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Climate change affects the stability and erosion of high‐alpine rock walls above glaciers (headwalls) that deliver debris to glacier surfaces. Since supraglacial debris in the ablation zone alters the melt behaviour of the underlying ice, the responses of debris‐covered glaciers and of headwalls to climate change may be coupled. In this study, we analyse the beryllium‐10 (10Be)‐cosmogenic nuclide concentration history of glacial headwalls delivering debris to the Glacier d'Otemma in Switzerland. By systematic downglacier‐profile‐sampling of two parallel medial moraines, we assess changes in headwall erosion through time for small, well‐defined debris source areas. We compute apparent headwall erosion rates from 10Be concentrations ([10Be]), measured in 15 amalgamated medial moraine debris samples. To estimate both the additional 10Be production during glacial debris transport and the age of our samples we combine our field‐based data with a simple model that simulates downglacier debris trajectories. Furthermore, we evaluate additional grain size fractions for eight samples to test for stochastic mass wasting effects on [10Be]. Our results indicate that [10Be] along the medial moraines vary systematically with time and consistently for different grain sizes. [10Be] are higher for older debris, closer to the glacier terminus, and lower for younger debris, closer to the glacier head. Computed apparent headwall erosion rates vary between ~0.6 and 10.8 mm yr−1, increasing over a maximum time span of ~200 years towards the present. As ice cover retreats, newly exposed headwall surfaces may become susceptible to enhanced weathering and erosion, expand to lower elevations, and contribute formerly shielded bedrock of likely different [10Be]. Hence, we suggest that recently lower [10Be] reflect the deglaciation of the debris source areas since the end of the Little Ice Age., In glacial landscapes, systematic downglacier‐sampling of medial moraine debris holds the potential to assess changes in headwall erosion through time. Cosmogenic beryllium‐10 (10Be) concentrations within the medial moraines of Glacier d'Otemma, Switzerland, broadly increase downglacier and translate into increasing headwall erosion rates towards the present. These trends may reflect processes associated with the exposure of new bedrock surfaces across recently deglaciating source headwalls., European Research Council (ERC) H2020‐EU.1.1., https://doi.org/10.5880/GFZ.3.3.2021.007

Oceanic circulation and mass‐field variability play important roles in exciting Earth's wobbles and length‐of‐day changes (ΔΛ), on time scales from days to several years. Modern descriptions of these effects employ oceanic angular momentum (OAM) series from numerical forward models or ocean state estimates, but nothing is known about how ocean reanalyses with sequential data assimilation (DA) would fare in that context. Here, we compute daily OAM series from three 1/4° global ocean reanalyses that are based on the same hydrodynamic core and input data (e.g., altimetry, Argo) but different DA schemes. Comparisons are carried out (a) among the reanalyses, (b) with an established ocean state estimate, and (c) with Earth rotation data, all focusing on the period 2006–2015. The reanalyses generally provide credible OAM estimates across a range of frequencies, although differences in amplitude spectra indicate a sensitivity to the adopted DA scheme. For periods less than 120 days, the reanalysis‐based OAM series explain ∼40%–50% and ∼30%–40% of the atmosphere‐corrected equatorial and axial geodetic excitation, similar to what is achieved with the state estimate. We find mixed performance of the reanalyses in seasonal excitation budgets, with some questionable mean ocean mass changes affecting the annual cycle in ΔΛ. Modeled excitations at interannual frequencies are more uncertain compared to OAM series from the state estimate and show hints of DA artifacts in one case. If users are to choose any of the tested reanalyses for rotation research, our study points to the Ocean Reanalysis System 5 as the most sensible choice., Key Points: We evaluate three ocean reanalyses for their skill in explaining Earth rotation variations on different time scales from 2006 to 2015. For periods, Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, https://resources.marine.copernicus.eu/product-detail/GLOBAL_REANALYSIS_PHY_001_031/INFORMATION, https://isdc.gfz-potsdam.de/ggfc-oceans/oam/, https://www.ncei.noaa.gov/access/metadata/landing-page/bin/iso?id=gov.noaa.ngdc.mgg.dem:316, https://podaac-tools.jpl.nasa.gov/drive/files/GeodeticsGravity/tellus/L3/mascon/RL06/JPL/v02/CRI/netcdf, https://keof.jpl.nasa.gov/combinations/

Tephra layers of the Mýtina Maar, Czech Republic, contain ferrimagnetic Mg–Al-rich titanomagnetite, which is suggested to originate from a fractionated alkaline CO2-rich lithospheric mantle melt. We investigated the magnetic mineralogy and Curie temperature (TC) from tephra deposits of two drill cores (, Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, CzechGeo/EPOS

Stibnite was mined until the end of the twentieth century in the Schlaining ore district, Austria, near the easternmost border of the Eastern Alps where windows of Penninic ophiolites and metasediments are exposed below Austroalpine tectonic units. In Early Miocene, structurally controlled small vein and metasomatic stibnite-quartz deposits were formed in Penninic Mesozoic calcareous marbles and calcite schists. Fluid inclusion studies identified two fluids involved in the mineralization: (i) a low-salinity, low-CO2 metamorphic fluid that precipitated quartz at approximately 240 °C and (ii) a stibnite-forming ore fluid that had a meteoric origin. There is no evidence of boiling or that the fluids mixed during mineralization. The ore components Sb and H2S were leached by fluid/rock interaction from buried rock units. Stibnite mineralization occurred by cooling the ore fluid to below 300 °C, at less than 2000 m depth. Quartz precipitated at slightly lower temperatures, approximately contemporaneous with stibnite. Fluid migration and ore deposition are probably related to high heat flow during the exhumation of the Rechnitz Window in response to Neogene extension and/or shallow Early Miocene andesitic magmatism. The study emphasizes that data obtained from the analyses of gangue minerals alone cannot routinely be used to infer the origin and depositional conditions of the associated ore minerals., Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ (4217)

To mitigate temporal aliasing effects in monthly mean global gravity fields from the GRACE and GRACE‐FO satellite tandem missions, both tidal and non‐tidal background models describing high‐frequency mass variability in atmosphere and oceans are needed. To quantify tides in the atmosphere, we exploit the higher spatial (31 km) and temporal (1 hr) resolution provided by the latest atmospheric ECMWF reanalysis, ERA5. The oceanic response to atmospheric tides is subsequently modeled with the general ocean circulation model MPIOM (in a recently revised TP10L40 configuration that includes the feedback of self‐attraction and loading to the momentum equations and has an improved bathymetry around Antarctica) as well as the shallow water model TiME (employing a much higher spatial resolution and more elaborate tidal dissipation than MPIOM). Both ocean models consider jointly the effects of atmospheric pressure variations and surface wind stress. We present the characteristics of 16 waves beating at frequencies in the 1–6 cpd band and find that TiME typically outperforms the corresponding results from MPIOM and also FES2014b as measured from comparisons with tide gauge data. Moreover, we note improvements in GRACE‐FO laser ranging interferometer range‐acceleration pre‐fit residuals when employing the ocean tide solutions from TiME, in particular, for the S1 spectral line with most notable improvements around Australia, India, and the northern part of South America., Plain Language Summary: In addition to many rather slow processes such as the melting of glaciers, rapid mass redistribution related to the weather also measurably affect the Earth's gravity field. The ability of monitoring liquid freshwater changes within the Earth system from the satellite gravity missions GRACE (2002–2017) and GRACE‐FO (since 2018) relies on accurate background models of mass variability in atmosphere and oceans for both tidal and non‐tidal processes. Atmospheric tides are primarily excited in the middle atmosphere by solar energy absorption at periods of 24 hr and its overtones. We find additional tidal signatures in the atmosphere excited by periodic deformations of both crust and sea‐surface of the Earth. We thus introduce here a new data set for the atmospheric tides and their corresponding oceanic response that features both more waves and higher accuracy than other background models previously used for the processing of GRACE and GRACE‐FO satellite gravimetry data., Key Points: Sixteen relevant tidal lines identified in hourly data from ERA5 atmospheric reanalysis. Dedicated simulations with a high‐resolution global hydrodynamic model to simulate ocean tides with atmospheric influence. New tidal models reduce pre‐fit residuals in GRACE‐FO Laser Ranging Interferometer data., Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, https://pypi.org/project/cdsapi/, https://mpimet.mpg.de/en/science/models/mpi-esm/mpiom, https://doi.org/10.5067/graod-1bg06

The intensity of the equatorial electrojet (EEJ) shows temporal and spatial variability that is not yet fully understood nor accurately modeled. Atmospheric solar tides are among the main drivers of this variability but determining different tidal components and their respective time series is challenging. It requires good temporal and spatial coverage with observations, which, previously could only be achieved by accumulating data over many years. Here, we propose a new technique for modeling the EEJ based on principal component analysis (PCA) of a hybrid ground‐satellite geomagnetic data set. The proposed PCA‐based model (PCEEJ) represents the observed EEJ better than the climatological EEJM‐2 model, especially when there is good local time separation among the satellites involved. The amplitudes of various solar tidal modes are determined from PCEEJ based tidal equation fitting. This allows to evaluate interannual and intraannual changes of solar tidal signatures in the EEJ. On average, the obtained time series of migrating and nonmigrating tides agree with the average climatology available from earlier work. A comparison of tidal signatures in the EEJ with tides derived from neutral atmosphere temperature observations show a remarkable correlation for nonmigrating tides such as DE3, DE2, DE4, and SW4. The results indicate that it is possible to obtain a meaningful EEJ spectrum related to solar tides for a relatively short time interval of 70 days., Key Points: A novel technique to model the equatorial electrojet (EEJ) based on the principal component analysis of a hybrid ground‐satellite data set. The new modeling matches observations better than the EEJM‐2 model, especially when the Swarm satellites have optimum local time coverage. Time series of migrating and nonmigrating tides amplitude in the EEJ are derived from 70‐day window., Coordenação de Aperfeiçoamento de Pessoal de Nível Superior http://dx.doi.org/10.13039/501100002322, Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro http://dx.doi.org/10.13039/501100004586, MEXT Japan Society for the Promotion of Science http://dx.doi.org/10.13039/501100001691

Earthquakes and slow‐slip events interact, however, detailed studies investigating their interplay are still limited. We generate the highest resolution microseismicity catalog to date for the northern Armutlu Peninsula in a ∼1‐year period to perform a detailed seismicity distribution analysis and correlate the results with a local, geodetically observed slow‐slip transient within the same period. Seismicity shows a transition of cluster‐type behavior from swarm‐like to burst‐like, accompanied by an increasing relative proportion of clustered (non‐Poissonian) relative to background (Poissonian) seismicity and gradually decreasing b‐value as the geodetically observed slow‐slip transient ends. The observed slow‐slip transient decay correlates with gradually increasing effective‐stress‐drop values. The observed correlation between the b‐value and geodetic transient highlights the influence of aseismic deformation on seismic deformation and the impact of slow‐slip transients on local seismic hazard., Plain Language Summary: Seismic and aseismic slip on faults can change the stress state in the crust and affect the recurrence time of earthquakes. Observations of how earthquakes and aseismic fault slip influence each other are limited because of the dearth of synchronous high‐resolution seismological and geodetic data. Here we use high‐resolution earthquake data in the northern Armutlu Peninsula along the Marmara seismic gap of the North Anatolian Fault (Turkey) to correlate the earthquake distribution with a local slow‐slip transient that occurred in the same period. We find that the slow‐slip transient modulates the spatiotemporal and frequency‐magnitude evolution of earthquakes, which highlights the influence of slow fault creep on fast fault slip. Our study demonstrates the importance of considering slow‐slip transients for seismic hazard assessment., Key Points: Seismicity analysis suggests that both external and internal forcing drive deformation in the Armutlu Peninsula. Temporal correlation between a slow‐slip transient and seismic b‐value highlights interactions between aseismic and seismic deformation. Slow‐slip transients modulate the frequency‐magnitude and spatiotemporal earthquake distribution., VW momentum grant, Helmotz Association Young Investigator Group http://dx.doi.org/10.13039/501100009318, Helmholtz‐Zentrum Potsdam—Deutsches GeoForschungs Zentrum GFZ, GIPP http://dx.doi.org/10.13039/501100010956

In this study, we present an empirical model of the equatorial electron pitch angle distributions (PADs) in the outer radiation belt based on the full data set collected by the Magnetic Electron Ion Spectrometer (MagEIS) instrument onboard the Van Allen Probes in 2012–2019. The PADs are fitted with a combination of the first, third and fifth sine harmonics. The resulting equation resolves all PAD types found in the outer radiation belt (pancake, flat‐top, butterfly and cap PADs) and can be analytically integrated to derive omnidirectional flux. We introduce a two‐step modeling procedure that for the first time ensures a continuous dependence on L, magnetic local time and activity, parametrized by the solar wind dynamic pressure. We propose two methods to reconstruct equatorial electron flux using the model. The first approach requires two uni‐directional flux observations and is applicable to low‐PA data. The second method can be used to reconstruct the full equatorial PADs from a single uni‐ or omnidirectional measurement at off‐equatorial latitudes. The model can be used for converting the long‐term data sets of electron fluxes to phase space density in terms of adiabatic invariants, for physics‐based modeling in the form of boundary conditions, and for data assimilation purposes., Plain Language Summary: Pitch angle distributions (PADs) are critically important for understanding the dynamics of trapped electrons in Earth's radiation belt region. Specific PAD types are linked to processes acting within the radiation belts which relate to the origins and loss mechanisms of the particle populations, as well as wave activity. In this study we present a polynomial model of the equatorial electron PADs at energies 30 keV–1.6 MeV with a continuous dependence on L‐shell, magnetic local time and activity driven by the solar wind dynamic pressure. The model can be used to reconstruct equatorial electron flux from observations at high latitudes and can be applied for converting the long‐term electron flux data sets to phase space density, driving the boundary conditions for the physics‐based simulations and for data assimilation., Key Points: A sum of the first, third, and fifth sine harmonics is used to approximate equatorial electron Pitch angle distributions (PADs) measured by the MagEIS detector onboard the Van Allen Probes. We present a PAD model with a continuous dependence on L, magnetic local time and activity, driven by the solar wind dynamic pressure. The model allows reconstructions of equatorial PADs from uni‐ and omni‐directional measurements at off‐equatorial latitudes., Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, Alexander von Humboldt‐Stiftung http://dx.doi.org/10.13039/100005156, https://doi.org/10.5880/GFZ.2.7.2022.001

The dynamics of the Alps and surrounding regions is still not completely understood, partly because of a non‐unique interpretation of its upper‐mantle architecture. In particular, it is unclear if interpreted slabs are consistent with the observed surface deformation and topography. We derive three end‐member scenarios of lithospheric thickness and slab geometries by clustering available shear‐wave tomography models into a statistical ensemble. We use these scenarios as input for geodynamic simulations and compare modeled topography, surface velocities and mantle flow to observations. We found that a slab detached beneath the Alps, but attached beneath the Northern Apennines captures first‐order patterns in topography and vertical surface velocities and can provide a causative explanation for the observed seismicity., Plain Language Summary: Present‐day surface deformation, including earthquakes, plate motion, and mass (re)distribution, results from processes operating at the surface and in the interior of the Earth. Understanding these processes and their coupling is of utmost importance in light of the hazard they pose to society. The Alps provide an excellent natural laboratory to understand such coupling. Here, we use seismic tomography models to constrain its upper‐mantle architecture. We further use these models to quantify forces originating from the resolved architecture and their effects on the present‐day surface deformation. The models can reproduce first‐order patterns in the observed topography and vertical surface motions. We found a causative correlation between the presence of a shallow slab attached to the overlying lithosphere in the Northern Apennines and the seismicity in the region. Our results allow us to better understand the transfer of internal forces to the surface, thereby helping to quantify the present‐day mechanical setup of the area., Key Points: Statistical ensemble of S‐wave tomography models is used to infer the Lithosphere‐Asthenosphere Boundary configuration and slab geometries in the Alps. The 3‐D upper‐mantle architecture from the statistics reproduce first‐order patterns in observed topography and Global Navigation Satellite Systems vertical velocities. A shallow/attached slab in the Northern Apennines is consistent with the mantle depth seismicity observed in this region., Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, https://doi.org/10.5880/GFZ.4.5.2019.004, https://gfzpublic.gfz-potsdam.de/pubman/item/item_238001, http://ds.iris.edu/ds/products/emc-earthmodels/, https://doi.org/10.5281/zenodo.7071571, https://doi.org/10.5281/zenodo.6538257

The lithospheric architecture of passive margins is crucial for understanding the tectonic processes that caused the breakup of Gondwana. We highlight the evolution of the South Atlantic passive margins by a simple thermal lithosphere‐asthenosphere boundary (LAB) model based on onset and cessation of rifting, crustal thickness, and stretching factors. We simulate lithospheric thinning and select the LAB as the T = 1,330°C isotherm, which is calculated by 1D advection and diffusion. Stretching factors and margin geometry are adjusted to state‐of‐the‐art data sets, giving a thermal LAB model that is especially designed for the continental margins of the South Atlantic. Our LAB model shows distinct variations along the passive margins that are not imaged by global LAB models, indicating different rifting mechanisms. For example, we model up to 200 km deep lithosphere in the South American Santos Basin and shallow lithosphere less than 60 km in the Namibe Basin offshore Africa. These two conjugate basins reflect a strong asymmetry in LAB depth that resembles variations in margin width. In a Gondwana reconstruction, we discuss these patterns together with seismic velocity perturbations for the Central and Austral Segments of the margins. The shallow lithosphere in the Namibe Basin correlates with signatures of the Angola Dome, attributed to epeirogenic uplift in the Neogene, suggesting an additional component of post‐breakup lithospheric thinning., Plain Language Summary: Passive margins mark the transition zone from a continent to the ocean without being an active boundary of tectonic plates. They are typical for all continents on the globe. In the South Atlantic, the passive margins are located adjacent to the eastern coastline of South America and the western coastline of Africa. Studying the architecture of passive margins is essential for understanding plate tectonic history of the earth because they define how the continents once fitted together and how they broke apart. Passive margin segments on opposite sides of an ocean form so called conjugate margin pairs. Most geophysical studies of passive margins focus on the first few kilometers under the surface. However, their deeper extension to the base of the rigid shell of the earth, known as lithospheric thickness, is to a large extent unknown. Based on a simple temperature model, we find that the lithospheric thickness is highly variable and shows large variations along the South Atlantic passive margins. These differences are associated with the extension of conjugate margin pairs: where one margin is narrower than the conjugate, its lithospheric thickness is greater. This asymmetry indicates that the geodynamic processes, causing the breakup of the two continents, must have been asymmetric as well. Offshore Angola, the lithosphere is modeled shallow and matches with relatively young rock signatures. This suggests additional tectonic activity on the African side after the breakup between the two continents occurred., Key Points: A simple thermal lithosphere‐asthenosphere boundary (LAB) model for the South Atlantic passive margins has been developed. The LAB model shows distinct variations along the margins that correlate with margin widths. Conjugate margin pairs reflect an asymmetry in LAB depth patterns that are locally related to post‐breakup lithospheric thinning., Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, https://doi.org/10.5880/GFZ.1.3.2020.006, https://www.earthbyte.org/webdav/ftp/Data_Collections/Muller_etal_2019_Tectonics/, https://doi.org/10.5281/zenodo.7074000, https://earthbyte.org/webdav/ftp/Data_Collections/Haas_etal_2022_Tectonics/

The Cenozoic strata of the Xining Basin, NE Tibet, have provided crucial records for understanding the tectonic and palaeo‐environmental evolution of the region. Yet, the age of the lower part of the sedimentary stratigraphy and, consequently, the early tectonic evolution of the basin remain debated. Here, we present the litho‐ and magnetostratigraphy of various early Eocene sections throughout the Xining Basin independently constrained by the U–Pb radiometric age of a carbonate bed. Our study extends the dated stratigraphy down to 53.0 Ma (C24n.1r) and reveals highly variable accumulation rates during the early Eocene ranging from 0.5 to 8 cm/ka. This is in stark contrast to the low but stable accumulation rates (2–3 cm/ka) observed throughout the overlying Palaeogene and Neogene strata. Such a pattern of basin infill is not characteristic of flexural subsidence as previously proposed, but rather supports an extensional origin of the Xining Basin with multiple depocentres, which subsequently coalesced into a more stable and slowly subsiding basin. Whether this extension was related to the far‐field effects of the subducting Pacific Plate or the India–Asia collision remains to be confirmed by future studies., European Research Council http://dx.doi.org/10.13039/501100000781, Hessisches Ministerium für Wissenschaft und Kunst http://dx.doi.org/10.13039/501100003495

Carbonate minerals are ubiquitous in most sediment-hosted mineral deposits. These deposits can contain a variety of carbonate types with complex paragenetic relationships. When normalized to chondritic values (CN), rare-earth elements and yttrium (REE+YCN) can be used to constrain fluid chemistry and fluid-rock interaction processes in both low- and high-temperature settings. Unlike other phases (e.g., pyrite), the application of in situ laser ablation-inductively coupled plasma-mass spectroscopy (LA-ICP-MS) data to the differentiation of pre-ore and hydrothermal carbonates remains relatively untested. To assess the potential applicability of carbonate in situ REE+Y data, we combined transmitted light and cathodoluminescence (CL) petrography with LA-ICP-MS analysis of carbonate mineral phases from (1) the Proterozoic George Fisher clastic dominated (CD-type) massive sulfide deposit and from (2) correlative, barren host rock lithologies (Urquhart Shale Formation). The REE+YCN composition of pre-ore calcite suggests it formed during diagenesis from diagenetic pore fluids derived from ferruginous, anoxic seawater. Hydrothermal and hydrothermally altered calcite and dolomite from George Fisher is generally more LREE depleted than the pre-ore calcite, whole-rock REE concentrations, and shale reference values. We suggest this is the result of hydrothermal alteration by saline Cl--rich mineralizing fluids. Furthermore, the presence of both positive and negative Eu/Eu* values in calcite and dolomite indicates that the mineralizing fluids were relatively hot (>250°C) and cooled below 200–250°C during ore formation. This study confirms the hypothesis that in situ REE+Y data can be used to differentiate between pre-ore and hydrothermal carbonate and provide important constraints on the conditions of ore formation., Helmholtz-Gemeinschaft http://dx.doi.org/10.13039/501100001656, https://doi.org/10.5880/GFZ.3.1.2020.005

The subduction of serpentinized slabs is the dominant process to transport “water” into Earth's mantle, and plays a pivotal role for subduction dynamics. Antigorite, the most abundant serpentine mineral in subduction settings, may imprint a seismic signature on serpentinized slabs, making them seismically distinguishable from the dry, non‐serpentinized ones. However, the complete single‐crystal elasticity of antigorite has not been experimentally constrained at high pressures, hindering the use of seismological approaches to detect serpentinization in subducting slabs. Here, we report the full elastic stiffness tensor of antigorite by single‐crystal Brillouin spectroscopy and X‐ray diffraction up to 7.71(5) GPa. We use our results to model seismic properties of antigorite‐bearing rocks and show that their seismological detectability depends on the geometrical relation between seismic wave paths and foliation of serpentinized rocks. In particular, we demonstrate that seismic shear anisotropy shows low sensitivity to serpentinization for a range of relevant geometries., Plain Language Summary: The subduction of serpentinized slabs plays a key role in the deep recycling of water into the Earth's interior. Antigorite is the main serpentine mineral in subducting slabs, and the most important carrier of water. Antigorite‐bearing rocks are predicted to have a distinct seismic signature, potentially allowing them to be detected with seismological approaches. However, our current knowledge on seismic properties of antigorite‐bearing rocks is limited, mostly hampered by a lack of experimental constraints on single‐crystal elasticity of antigorite at relevant pressures. In this study, state‐of‐the‐art techniques were employed to produce the first experimental description of the complete high‐pressure elasticity of antigorite single crystals. Our experimental data set was implemented in the modeling of seismic properties of antigorite‐bearing rocks at pressures relevant for subduction. Our results were used to discuss the relation between seismic wave path and shear wave anisotropy in serpentinized slabs, and challenge the use of shear wave splitting as a proxy for serpentinization in slabs., Key Points: Single‐crystal elasticity of antigorite at high pressures is determined by Brillouin spectroscopy and X‐ray diffraction experiments. Seismic signature of serpentinized slabs is constrained in a relevant composition‐pressure space. Serpentinization in slabs may be undetectable through shear wave anisotropy., Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, EC Horizon 2020 Framework Programme http://dx.doi.org/10.13039/100010661, https://doi.org/10.6084/m9.figshare.20348748, https://doi.org/10.6084/m9.figshare.20348781

In this study, we investigated the phase stability of Al‐free and Al‐bearing superhydrous phase B (shy‐B) up to 55 GPa and 2500 K. In comparison with Al‐free shy‐B, the incorporation of 11.7 wt.% Al2O3 in shy‐B expands the stability by ∼400–800 K at 20–30 GPa. The determined dehydration boundary for Al‐bearing phase D indicates that it could be present even at normal mantle geotherm conditions at 30–40 GPa. Up to 23.8 mol.% Al2O3 can be dissolved into the structures of akimotoite and bridgmanite as a result of the decomposition reactions of Al‐bearing shy‐B and phase D between 20 and 40 GPa. Results of further experiments indicate that δ‐AlOOH is the stable hydrous phase coexisting with Al‐depleted bridgmanite at pressures above 52 GPa. This study shows that the incorporation of Al in dense hydrous magnesium silicates can have a profound impact on our picture of the water cycle in the deep Earth., Plain Language Summary: Constraining the deep cycle of water has a tremendous impact on our picture of the current state of the Earth and the evolution of the Earth's interior. Dense hydrous magnesium silicates (DHMSs) are considered potential H2O carriers in the Earth's mantle. However, the DHMSs can only be present at the relatively cold conditions of subduction slabs due their limited thermal stability. We determined the phase stability of Al‐bearing DHMSs at high pressure and temperature (P‐T) conditions. Our results show that the thermal stability of Al‐bearing shy‐B extends by 400–800 K with respect to its Al‐free counterpart at 600–800 km depth. The incorporation of Al also expands the phase stability of phase D and enhances the likelihood of its occurrence at normal mantle conditions at 800–1100 km. In addition, we observe that 23.8 mol.% Al2O3 can be dissolved into the structures of akimotoite and bridgmanite as a result of the decomposition reactions of Al‐bearing shy‐B and phase D between 600 and 100 km depth. Furthermore, δ‐AlOOH is the stable hydrous phase coexisting with Al‐depleted bridgmanite in the MgO‐SiO2‐Al2O3‐H2O system at pressures above 52 GPa and 1500 K., Key Points: In comparison with Al‐free shy‐B, the incorporation of 11.7 wt.% Al2O3 in superhydrous phase B (shy‐B) expands the stability by ∼400–800 K at 20–30 GPa. Al‐bearing phase D could be present even at normal mantle geotherm conditions at 30–40 GPa. δ‐AlOOH is the stable hydrous phase coexisting with Al‐depleted bridgmanite at pressures above 52 GPa., Center for Molecular Water Science, CMWS, https://doi.org/10.5281/zenodo.6320835

An earthquake‐induced stress drop on a megathrust instigates different responses on the upper plate and slab. We mimic homogenous and heterogeneous megathrust interfaces at the laboratory scale to monitor the strain relaxation on two elastically bi‐material plates by establishing analog velocity weakening and neutral materials. A sequential elastic rebound follows the coseismic shear‐stress drop in our elastoplastic‐frictional models: a fast rebound of the upper plate and the delayed and smaller rebound on the elastic belt (model slab). A combination of the rebound of the slab and the rapid relaxation (i.e., elastic restoration) of the upper plate after an elastic overshooting may accelerate the relocking of the megathrust. This acceleration triggers/antedates the failure of a nearby asperity and enhances the early slip reversal in the rupture area. Hence, the trench‐normal landward displacement in the upper plate may reach a significant amount of the entire interseismic slip reversal and speeds up the stress build‐up on the upper plate backthrust that emerges self‐consistently at the downdip end of the seismogenic zones. Moreover, the backthrust switches its kinematic mode from a normal to reverse mechanism during the coseismic and postseismic stages, reflecting the sense of shear on the interface., Plain Language Summary: Subduction zones, where one tectonic plate slides underneath the other, host the largest earthquakes on earth. Two plates with different physical properties define the upper and lower plates in the subduction zones. A frictional interaction at the interface between these plates prevents them from sliding and builds up elastic strain energy until the stress exceeds their strength and releases accumulated energy as an earthquake. The source of the earthquake is located offshore; hence illuminating the plates' reactions to the earthquakes is not as straightforward as the earthquakes that occur inland. Here we mimic the subduction zone at the scale of an analog model in the laboratory to generate analog earthquakes and carefully monitor our simplified model by employing a high‐resolution monitoring technique. We evaluate the models to examine the feedback relationship between upper and lower plates during and shortly after the earthquakes. We demonstrate that the plates respond differently and sequentially to the elastic strain release: a seaward‐landward motion of the upper plate and an acceleration in the lower plate sliding underneath the upper plate. Our results suggest that these responses may trigger another earthquake in the nearby region and speed up the stress build‐up on other faults., Key Points: Seismotectonic scale models provide high‐resolution observations to study the surface deformation signals from shallow megathrust earthquakes. Surface displacement time‐series suggest a sequential elastic rebound of the upper plate and slab during great subduction megathrust earthquakes. Slip reversal may be caused by rapid restoration of the upper plate after overshooting and amplified upper plate motion., SUBITOP Marie Sklodowska‐Curie Action project from the European Union's EU Framework Programme, Deutsche Forschungsgemeinschaft, https://doi.org/10.5880/fidgeo.2022.024

The Atmosphere and Ocean De‐Aliasing Level‐1B (AOD1B) product provides a priori information about temporal variations in the Earth's gravity field induced by non‐tidal circulation processes in atmosphere and ocean. It is routinely applied as a background model in the Gravity Recovery and Climate Experiment (GRACE)/GRACE Follow‐On (GRACE‐FO) satellite gravimetry data processing. We here present three new datasets in preparation for the upcoming release RL07 of AOD1B, that are based on either the global ERA5 reanalysis or the ECMWF operational data together with simulations from the Max‐Planck‐Institute for Meteorology general circulation model forced consistently with the fields of the same atmospheric data set. The oceanic simulations newly include an updated bathymetry around Antarctica including cavities under the ice shelves, the explicit implementation of the feedback effects of self‐attraction and loading to ocean dynamics as well as a refined harmonic tidal analysis. Comparison to the current release of AOD1B in terms of GRACE‐FO K‐band range‐acceleration pre‐fit residuals, LRI line‐of‐sight gravity differences and band‐pass filtered altimetry data reveals an overall improvement in the representation of the high‐frequency mass variability. Potential benefits of enhancing the temporal resolution remain inconclusive so that the upcoming release 07 will be sampled again every 3 hr., Plain Language Summary: Satellite gravimetry missions such as the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow‐On (GRACE‐FO), which play a vital role in the monitoring of the Earth's mass transports, require a priori background information on the high‐frequency mass variations which can not be resolved by the monthly gravity solutions. The Atmosphere and Ocean De‐Aliasing Level‐1B (AOD1B) data product provides the required background information for non‐tidal high‐frequency mass changes in the atmosphere and oceans. However, the accurate representation of these mass variations remains challenging and deficiencies in the background models have a significant impact on the overall gravity field errors. Thus, we here present three new datasets in preparation for an upcoming release of AOD1B (RL07). The datasets improve over previous releases by incorporating the effects of the self attraction and solid earth deformation caused by anomalous water masses (SAL), an improved representation of the bathymetry and atmospheric forcing around Antarctica, making use of the new ERA5 atmospheric reanalysis as well as an updated estimation and subtraction of atmospherically induced tidal signals. We compare the new data to the previous release of AOD1B using microwave‐ and laser‐ranging data from GRACE‐FO as well as Jason‐3 altimetry data and show a global improvement in the representation of high‐frequency mass changes., Key Points: Atmospheric mass variability from ECMWF’s latest global reanalysis ERA5 is discussed. Ocean response from Max‐Planck‐Institute for Meteorology Ocean Model includes feedback of self‐attraction and loading. Applicable for Gravity Recovery and Climate Experiment (GRACE), GRACE Follow‐On, and legacy data from SLR satellites., Deutsche Forschungsgemeinschaft, DFG http://dx.doi.org/10.13039/501100001659, https://doi.org/10.5880/GFZ.1.3.2022.003

Faults and fractures can be permeable pathways for focused fluid flow in structurally controlled ore‐forming hydrothermal systems. However, quantifying their role in fluid flow on the scale of several kilometers with numerical models typically requires high‐resolution meshes. This study introduces a modified numerical representation of m‐scale fault zones using lower‐dimensional elements (here, one‐dimensional [1D] elements in a 2D domain) to resolve structurally controlled fluid flow with coarser mesh resolutions and apply the method to magmatic‐hydrothermal ore‐forming systems. We modeled horizontal and vertical structure‐controlled magmatic‐hydrothermal deposits to understand the role of permeability and structure connectivity on ore deposition. The simulation results of vertically extended porphyry copper systems show that ore deposition can occur along permeable vertical structures where ascending, overpressured magmatic fluids are cooled by downflowing ambient fluids. Structure permeability and fault location control the distribution of ore grades. In highly permeable structures, the mineralization can span up to 3 km vertically, resulting in heat‐pipe mechanisms that promote the ascent of a magmatic vapor phase to an overlying structurally controlled epithermal system. Simulations for the formation of subhorizontal vein‐type deposits suggest that the major control on fluid flow and metal deposition along horizontal structures is the absence of vertical structures above the injection location but their presence at greater distances. Using a dynamic permeability model mimicking crack‐seal mechanisms within the structures leads to a pulsating behavior of fracture‐controlled hydrothermal systems and prevents the inflow of ambient fluids under overpressured conditions., Plain Language Summary: Faults and fractures can serve as permeable pathways for focused fluid flow in the subsurface and therefore be essential geological features for the formation of economic mineral deposits. However, quantifying their role in the hydrothermal systems on the scale of several kilometers with numerical models typically requires high‐resolution meshes. This study presents a modified numerical representation of m‐scale fault zones with variable orientations to understand the hydrology of magmatic‐hydrothermal ore‐forming systems. The vertically extended systems simulation results show that ore deposition can occur along permeable vertical structures where ascending magmatic fluids are cooled by downflowing ambient fluids. Structure permeability and fault location can directly control the distribution of ore grades. In contrast, mineralization in horizontal structures requires the absence of vertical structures above the injection location of metal‐bearing magmatic volatiles but their presence at greater distances. Our model also shows how dynamic opening and closing of the structures in response to magmatic degassing can lead to a pulsating behavior and prevent the downflow of ambient fluids., Key Points: We describe structurally controlled fluid flow by representing faults and fractures as one‐dimensional line elements within a 2D modeling domain. Vertical structures are efficient pathways for focused fluid flow and formation of high‐grade mineralization. Ore formation in horizontal fractures requires a hydraulic connection to distal vertical fault zones., German Federal Ministry of Education and Research, Deutsche Forschungsgemeinschaft, DFG http://dx.doi.org/10.13039/501100001659, Helmholtz Recruitment Initiative

Modeling studies have predicted that the acoustic resonance of the atmosphere during geophysical events such as earthquakes and volcanos can lead to an oscillation of the geomagnetic field with a frequency of about 4 mHz. However, observational evidence is still limited due to scarcity of suitable events. On 15 January 2022, the submarine volcano Hunga Tonga‐Hunga Ha'apai (20.5°S, 175.4°W, Tonga) erupted in the Pacific Ocean and caused severe atmospheric disturbance, providing an opportunity to investigate geomagnetic effects associated with acoustic resonance. Following the eruption, geomagnetic oscillation is observed at Apia, approximately 835 km from Hunga Tonga, mainly in the Pc 5 band (150–600 s, or 1.7–6.7 mHz) lasting for about 2 hr. The dominant frequency of the oscillation is 3.8 mHz, which is consistent with the frequency of the atmospheric oscillation due to acoustic resonance. The oscillation is most prominent in the eastward (Y) component, with an amplitude of ∼3 nT, which is much larger than those previously reported for other events (2700 km). However, geomagnetic oscillation with a much smaller amplitude (∼0.3 nT) is observed at Honolulu, which is located near the magnetic conjugate point of Hunga Tonga, in a similar wave form as at Apia, indicating interhemispheric coupling. This is the first time that geomagnetic oscillations due to the atmospheric acoustic resonance are simultaneously detected at magnetic conjugate points., Key Points: The effect of the January 2022 Hunga Tonga‐Hunga Ha’apai volcano eruption on the geomagnetic field is examined. Geomagnetic oscillation with a frequency of ∼3.8 mHz is observed simultaneously near the volcano and its magnetic conjugate point. The oscillation is attributed to the acoustic resonance of the atmosphere., Coordenação de Aperfeiçoamento de Pessoal de Nível Superior http://dx.doi.org/10.13039/501100002322, Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, https://www.intermagnet.org/data-donnee/download-eng.php

Volcano‐seismic signals such as long‐period events and tremor are important indicators for volcanic activity and unrest. However, their wavefield is complex and characterization and location using traditional seismological instrumentation is often difficult. In 2019 we recorded the full seismic wavefield using a newly developed 3C rotational sensor co‐located with a 3C traditional seismometer on Etna, Italy. We compare the performance of the rotational sensor, the seismometer and the Istituto Nazionale di Geofisica e Vulcanologia‐Osservatorio Etneo (INGV‐OE) seismic network with respect to the analysis of complex volcano‐seismic signals. We create event catalogs for volcano‐tectonic (VT) and long‐period (LP) events combining a STA/LTA algorithm and cross‐correlations. The event detection based on the rotational sensor is as reliable as the seismometer‐based detection. The LP events are dominated by SH‐type waves. Derived SH phase velocities range from 500 to 1,000 m/s for LP events and 300–400 m/s for volcanic tremor. SH‐waves compose the tremor during weak volcanic activity and SH‐ and SV‐waves during sustained strombolian activity. We derive back azimuths using (a) horizontal rotational components and (b) vertical rotation rate and transverse acceleration. The estimated back azimuths are consistent with the INGV‐OE event location for (a) VT events with an epicentral distance larger than 3 km and some closer events, (b) LP events and tremor in the main crater area. Measuring the full wavefield we can reliably analyze the back azimuths, phase velocities and wavefield composition for VT, LP events and tremor in regions that are difficult to access such as volcanoes., Plain Language Summary: Traditional seismographs usually include mass and spring systems which measure vibrations constrained to up‐down, north‐south and east‐west directions. We compare the traditional seismometer to a rotational sensor which measures ground rotation around the same three directions. We installed a rotational sensor on Etna volcano in 2019 to test these new sensors in a volcanic environment. We compare the performance of the rotational sensor, a traditional seismometer and the Istituto Nazionale di Geofisica e Vulcanologia‐Osservatorio Etneo (INGV‐OE) seismometer network. We detect two types of a few second long earthquakes and find that the rotational sensor performs as good as the seismometer. We use the rotational sensor to calculate directions of the earthquake locations and find that most directions agree with the INGV‐OE network location and the area of the active craters. We find that for some earthquakes the ground only moved horizontally while for others it also moved up and down. Using a rotational sensor on a volcano we can easily and reliably estimate the ground motion, the speed of the earthquake waves in the ground and understand better how these earthquakes are generated., Key Points: We tested the performance of a rotational sensor compared to a seismometer and a seismic network using long‐period (LP), volcano‐tectonic (VT) events and tremor on Etna. LP and VT events are dominated by SH‐ and SV‐waves, respectively. Tremor changed from SH‐ to a mixed wavefield during strombolian eruptions. LP event and tremor back azimuths point to the main craters consistent with the Istituto Nazionale di Geofisica e Vulcanologia location; VT event back azimuths are at times consistent., Eurovolc, Daimler Benz Foundation, https://doi.org/10.14470/ME7564062119

The southern Central Andes (SCA) (between 27° S and 40° S) is bordered to the west by the convergent margin between the continental South American Plate and the oceanic Nazca Plate. The subduction angle along this margin is variable, as is the deformation of the upper plate. Between 33° S and 35° S, the subduction angle of the Nazca plate increases from sub-horizontal (, Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, Federal State of Brandenburg, Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ (4217)

The Big Naryn Complex (BNC) in the East Djetim-Too Range of the Kyrgyz Middle Tianshan block is a tectonized, at least 2 km thick sequence of predominantly felsic to intermediate volcanic rocks intruded by porphyric rhyolite sills. It overlies a basement of metamorphic rocks and is overlain by late Neoproterozoic Djetim-Too Formation sediments; these also occur as tectonic intercalations in the BNC. The up to ca. 1100 m thick Lower Member is composed of predominantly rhyolites-to-dacites and minor basalts, while the at least 900 m thick pyroclastic Upper Member is dominated by rhyolitic-to-dacitic ignimbrites. Porphyric rhyolite sills are concentrated at the top of the Lower Member. A Lower Member rhyolite and a sill sample have LA-ICP-MS U–Pb zircon crystallization ages of 726.1 ± 2.2 Ma and 720.3 ± 6.5 Ma, respectively, showing that most of the magmatism occurred within a short time span in the late Tonian–early Cryogenian. Inherited zircons in the sill sample have Neoarchean (2.63, 2.64 Ga), Paleo- (2.33–1.81 Ga), Meso- (1.55 Ga), and Neoproterozoic (ca. 815 Ma) ages, and were derived from a heterogeneous Kuilyu Complex basement. A 1751 ± 7 Ma 40Ar/39Ar age for amphibole from metagabbro is the age of cooling subsequent to Paleoproterozoic metamorphism of the Kuilyu Complex. The large amount of pyroclastic rocks, and their major and trace element compositions, the presence of Neoarchean to Neoproterozoic inherited zircons and a depositional basement of metamorphic rocks point to formation of the BNC in a continental magmatic arc setting., Akademie Věd České Republiky http://dx.doi.org/10.13039/501100004240, Universität Potsdam (1031)

Clustering algorithms can be applied to seismic catalogs to automatically classify earthquakes upon the similarity of their attributes, in order to extract information on seismicity processes and faulting patterns out of large seismic datasets. We describe here a Python open-source software for density-based clustering of seismicity named seiscloud, based on the pyrocko library for seismology. Seiscloud is a tool to dig data out of large local, regional, or global seismic catalogs and to automatically recognize seismicity clusters, characterized by similar features, such as epicentral or hypocentral locations, origin times, focal mechanisms, or moment tensors. Alternatively, the code can rely on user-provided distance matrices to identify clusters of events sharing indirect features, such as similar waveforms. The code can either process local seismic catalogs or download selected subsets of seismic catalogs, accessing different global seismicity catalog providers, perform the seismic clustering over different steps in a flexible, easily adaptable approach, and provide results in form of declustered seismic catalogs and a number of illustrative figures. Here, the algorithm usage is explained and discussed through an application to Northern Chile seismicity., Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ (4217)

During the last few years, the determination of high-resolution global gravity field has gained momentum due to high-accuracy satellite-derived observations and development of forward gravity modelling. Forward modelling computes the global gravitational field from mass distribution sources instead of actual gravity measurements and helps improving and complementing the medium to high-frequency components of the global gravity field models. In this study, we approximate the global gravity potential of the Earth’s upper crust based on ellipsoidal approximation and a mass layer concept. Such an approach has an advantage of spectral methods and also avoids possible instabilities due to the use of a sequence of thin ellipsoidal shells. Lateral density within these volumetric shells bounded by confocal lower and upper shell ellipsoids is used in the computation of the ellipsoidal harmonic coefficients which are then transformed into spherical harmonic coefficients on the Earth’s surface in the final step. The main outcome of this research is a spectral representation of the gravitatioal potential of the Earth’s upper crust, computed up to degree and order 3660 in terms of spherical harmonic coefficients (ROLI_EllApprox_SphN_3660). We evaluate our methodology by comparing this model with other similar forward models in the literature which show sub-cm agreement in terms of geoid undulations. Finally, EIGEN-6C4 is augmented by ROLI_EllApprox_SphN_3660 and the gravity field functionals computed from the expanded model which has about 5 km half-wavelength spatial resolution are compared w.r.t. ground-truth data in different regions worldwide. Our investigations show that the contribution of the topographic model increases the agreement up to ~ 20% in the gravity value comparisons.

Megathrust earthquakes impose changes of differential stress and pore pressure in the lithosphere‐asthenosphere system that are transiently relaxed during the postseismic period primarily due to afterslip, viscoelastic and poroelastic processes. Especially during the early postseismic phase, however, the relative contribution of these processes to the observed surface deformation is unclear. To investigate this, we use geodetic data collected in the first 48 days following the 2010 Maule earthquake and a poro‐viscoelastic forward model combined with an afterslip inversion. This model approach fits the geodetic data 14% better than a pure elastic model. Particularly near the region of maximum coseismic slip, the predicted surface poroelastic uplift pattern explains well the observations. If poroelasticity is neglected, the spatial afterslip distribution is locally altered by up to ±40%. Moreover, we find that shallow crustal aftershocks mostly occur in regions of increased postseismic pore‐pressure changes, indicating that both processes might be mechanically coupled., Plain Language Summary: Large earthquakes modify the state of stress and pore pressure in the upper crust and mantle. These changes induce stress relaxation processes and pore pressure diffusion in the postseismic phase. The two main stress relaxation processes are postseismic slip along the rupture plane of the earthquake and viscoelastic deformation in the rock volume. These processes decay with time, but can sustain over several years or decades, respectively. The other process that results in volumetric crustal deformation is poroelasticity due to pore pressure diffusion, which has not been investigated in detail. Using postseismic surface displacement data acquired by radar satellites after the 2010 Maule earthquake, we show that poroelastic deformation may considerably affect the vertical component of the observed geodetic signal during the first months. Poroelastic deformation also has an impact on the estimation of the postseismic slip, which in turn affects the energy stored at the fault plane that is available for the next event. In addition, shallow aftershocks within the continental crust show a good, positive spatial correlation with regions of increased postseismic pore‐pressure changes, suggesting they are linked. These findings are thus important to assess the potential seismic hazard of the segment., Key Points: A poro‐viscoelastic deformation model improves the geodetic data misfit by 14% compared to an elastic model that only accounts for afterslip. Poroelastic deformation mainly produces surface uplift and landward displacement patterns on the coastal forearc region. Neglecting poroelastic effects may locally alter the afterslip amplitude by up to ±40% near the region of maximum coseismic slip., Helmholtz Association (亥姆霍兹联合会致力) http://dx.doi.org/10.13039/501100009318

The behavior of the shallow portion of the subduction zone, which generates the largest earthquakes and devastating tsunamis, is still insufficiently constrained. Monitoring only a fraction of a single megathrust earthquake cycle and the offshore location of the source of these earthquakes are the foremost reasons for the insufficient understanding. The frictional‐elastoplastic interaction between the megathrust interface and its overlying wedge causes variable surface strain signals such that the wedge strain patterns may reveal the mechanical state of the interface. To contribute to this understanding, we employ Seismotectonic Scale Modeling and simplify elastoplastic megathrust subduction to generate hundreds of analog seismic cycles at a laboratory scale and monitor the surface strain signals over the model's forearc across high to low temporal resolutions. We establish two compressional and critical wedge configurations to explore the mechanical and kinematic interaction between the shallow wedge and the interface. Our results demonstrate that this interaction can partition the wedge into different segments such that the anelastic extensional segment overlays the seismogenic zone at depth. Moreover, the different segments of the wedge may switch their state from compression/extension to extension/compression domains. We highlight that a more segmented upper plate represents megathrust subduction that generates more characteristic and periodic events. Additionally, the strain time series reveals that the strain state may remain quasi‐stable over a few seismic cycles in the coastal zone and then switch to the opposite mode. These observations are crucial for evaluating earthquake‐related morphotectonic markers and short‐term interseismic time series of the coastal regions., Key Points: Analog earthquake cycle experiments provide observations to evaluate the surface strain signals from the shallow megathrust. The extensional segment of the forearc overlays the seismogenic zone at depth. The strain state may remain quasi‐stable over a few seismic cycles in the coastal zone., SUBITOP Marie Sklodowska‐Curie Action project from the European Union's EU Framework Programme, Deutsche Forschungsgemeinschaft (CRC 1114) “Scaling Cascades in Complex Systems”, https://doi.org/10.5880/fidgeo.2022.015

To explore the dynamic mechanism of continental rifting within a convergent setting, we determine the first P wave radial anisotropic tomography beneath the Woodlark rift in southeastern Papua New Guinea, which develops within the obliquely colliding zone between the Australian and southwest Pacific plates. The rift zone is depicted as localized low‐velocity anomalies with positive radial anisotropy, which rules out a dominant role of active mantle upwelling in promoting the rift development and favors passive rifting with decompression melting as main processes. Downwelling slab relics in the upper mantle bounding the rift zone are revealed based on observed high‐velocity anomalies and negative radial anisotropy, which may contribute to the ultra‐high pressure rock exhumations and rift initiation. Our observations thus indicate that the Woodlark rift follows a passive model and is mainly driven by slab pull from the northward subduction of the Solomon plate., Plain Language Summary: The Woodlark rift in Papua New Guinea develops within the shear zone between the Australian and southwest Pacific plates and is one of the youngest and most rapidly extending continental rifts in the world. In this work, we analyze teleseismic P wave arrivals to study both 3‐D velocity and radial anisotropy structures of the upper mantle, offering new evidence to understand rift initiation under a generally convergent setting. Slab remnants in the upper mantle bordering the rift zone are detected and sinking into the deeper mantle. Downwelling of these slab segments may induce small scale return flows in the mantle and contribute to exhumation of the ultra‐high pressure rocks and rift development. Significant low‐velocity anomalies are revealed beneath the rift zone and have consistently positive radial anisotropy, which indicates a dominant strain in the horizontal plane and supports a passive rifting model, where mantle material is brought to shallower depths simply as a result of the extension of the lithosphere and melt is produced due to the lowered melting point at reduced pressure (decompression melting). Tensional stresses transferred from slab pull of the northward Solomon subduction are probably driving the rifting., Key Points: P wave radial anisotropic structure beneath the young and highly extended Woodlark rift is constrained from teleseismic tomography. Downwelling of slab relics bordering the rift zone may contribute to ultra‐high pressure rock exhumation and rift development. Slab‐pull drives rift initiation and induces decompression melting in the upper mantle under the rift zone by horizontal stress transfer., National Natural Science Foundation of China (NSFC) http://dx.doi.org/10.13039/501100001809, National Science Foundation (NSF) http://dx.doi.org/10.13039/100000001, MEXT | Japan Society for the Promotion of Science (JSPS) http://dx.doi.org/10.13039/501100001691, Alexander von Humboldt‐Stiftung (Humboldt‐Stiftung) http://dx.doi.org/10.13039/100005156, https://doi.org/10.7914/SN/XD_1999, https://doi.org/10.7914/SN/ZN_2010

Shallow earthquakes frequently disturb the hydrological and mechanical state of the subsurface, with consequences for hazard and water management. Transient post‐seismic hydrological behavior has been widely reported, suggesting that the recovery of material properties (relaxation) following ground shaking may impact groundwater fluctuations. However, the monitoring of seismic velocity variations associated with earthquake damage and hydrological variations are often done assuming that both effects are independent. In a field site prone to highly variable hydrological conditions, we disentangle the different forcing of the relative seismic velocity variations δv retrieved from a small dense seismic array in Nepal in the aftermath of the 2015 Mw 7.8 Gorkha earthquake. We successfully model transient damage effects by introducing a universal relaxation function that contains a unique maximum relaxation timescale for the main shock and the aftershocks, independent of the ground shaking levels. Next, we remove the modeled velocity from the raw data and test whether the corresponding residuals agree with a background hydrological behavior we inferred from a previously calibrated groundwater model. The fitting of the δv data with this model is improved when we introduce transient hydrological properties in the phase immediately following the main shock. This transient behavior, interpreted as an enhanced permeability in the shallow subsurface, lasts for ∼6 months and is shorter than the damage relaxation (∼1 yr). Thus, we demonstrate the capability of seismic interferometry to deconvolve transient hydrological properties after earthquakes from non‐linear mechanical recovery., Plain Language Summary: Earthquake ground shaking damage the rocks in the subsurface of the Earth, altering their strength and their permeability. After the main shock, the rock properties slowly return to their pre‐earthquake state, but the duration of this recovery is poorly constrained. One way to investigate these time‐dependent changes is through the monitoring of seismic velocity inferred from ambient ground vibration recorded at seismic stations. Here, we constrain the evolution of seismic velocity following the large 2015 Mw 7.8 Gorkha earthquake in Nepal, in a field site characterized by seasonal groundwater fluctuations. We find that the velocity recoveries after the main shock and the aftershocks can be modeled with the same recovery timescale, independently from the initial shaking intensity. This suggests that earthquakes of different sizes activate the same geological structures and mechanisms during the recovery phase. Thanks to the unique hydrological setting of our field site and a model that links seismic velocity and groundwater level, we also show that this change of rock properties after the main shock is accompanied by a transient change in hydrological properties, an observation inferred for the first time with seismic measurement., Key Points: We estimate a recovery time scale (, GFZ HART program, https://doi.org/10.5880/GFZ.4.6.2021.002, https://doi.org/10.14470/KA7560056170

We investigate induced seismicity associated with a hydraulic stimulation campaign performed in 2020 in the 5.8 km deep geothermal OTN‐2 well near Helsinki, Finland as part of the St1 Deep Heat project. A total of 2,875 m3 of fresh water was injected during 16 days at well‐head pressures −1.9 ${M}_{\mathrm{L}}^{\mathrm{H}\mathrm{e}\mathrm{l}} > -1.9$ were recorded during and after the stimulation campaign. The analyzed statistical parameters include magnitude‐frequency b‐value, interevent time and interevent time ratio, as well as magnitude correlations. We find that the b‐value remained stationary for the entire injection period suggesting limited stress build‐up or limited fracture network coalescence in the reservoir. The seismicity during the stimulation neither shows signatures of magnitude correlations, nor temporal clustering or anticlustering beyond those arising from varying injection rates. The interevent time statistics are characterized by a Poissonian time‐varying distribution. The calculated parameters indicate no earthquake interaction. Focal mechanisms suggest that the injection activated a spatially distributed network of similarly oriented fractures. The seismicity displays stable behavior with no signatures pointing toward a runaway event. The cumulative seismic moment is proportional to the cumulative hydraulic energy and the maximum magnitude is controlled by injection rate. The performed study provides a base for implementation of time‐dependent probabilistic seismic hazard assessment for the project site., Plain Language Summary: We investigate anthropogenic seismicity associated with fluid injection into the 5.8 km deep geothermal OTN‐2 well near Helsinki, Finland, as a part of St1 Deep Heat Project. A total of 2,875 m3 of fresh water was injected during 16 days at well‐head pressures, Key Points: Induced seismicity associated with stimulation campaign in a 5.8 km deep geothermal OTN‐2 well passively responds to injection operations. Seismicity is a non‐stationary Poisson process with seismicity rate and maximum magnitude modulated by the hydraulic energy input rate. Seismicity clusters in space and time in response to fluid injection but no interaction between earthquakes is observed., Helmholtz Association http://dx.doi.org/10.13039/501100009318, https://doi.org/10.5880/GFZ.4.2.2022.001

The spatial and angular emission patterns of artificial and natural light emitted, scattered, and reflected from the Earth at night are far more complex than those for scattered and reflected solar radiation during daytime. In this commentary, we use examples to show that there is additional information contained in the angular distribution of emitted light. We argue that this information could be used to improve existing remote sensing retrievals based on night lights, and in some cases could make entirely new remote sensing analyses possible. This work will be challenging, so we hope this article will encourage researchers and funding agencies to pursue further study of how multi‐angle views can be analyzed or acquired., Plain Language Summary: When satellites take images of Earth, they usually do so from directly above (or as close to it as is reasonably possible). In this comment, we show that for studies that use imagery of Earth at night, it may be beneficial to take several images of the same area at different angles within a short period of time. For example, different types of lights shine in different directions (street lights usually shine down, while video advertisements shine sideways), and tall buildings can block the view of a street from some viewing angles. Additionally, since views from different directions pass through different amounts of air, imagery at multiple angles could be used to obtain information about Earth's atmosphere, and measure artificial and natural night sky brightness. The main point of the paper is to encourage researchers, funding agencies, and space agencies to think about what new possibilities could be achieved in the future with views of night lights at different angles., Key Points: Remote sensing using the visible band at night is more complex than during the daytime, especially due to the variety of artificial lights. Views of night lights intentionally taken from multiple angles provide several advantages over near‐nadir or circumstantial view geometries. Night lights remote sensing would benefit from greater consideration of the role viewing geometry plays in the observed radiance., EC H2020 H2020 Societal Challenges http://dx.doi.org/10.13039/100010676, Helmholtz Association http://dx.doi.org/10.13039/501100009318, Slovak Research and Development Agency, Xunta de Galicia (Regional Government of Galicia) http://dx.doi.org/10.13039/501100010801, National Aeronautics and Space Administration http://dx.doi.org/10.13039/100000104, University of Hong Kong http://dx.doi.org/10.13039/501100003803, Fonds de recherche du Québec, EC Emprego, Assuntos Sociais e Inclusão European Social Fund http://dx.doi.org/10.13039/501100004895, Natural Environment Research Council http://dx.doi.org/10.13039/501100000270, City of Cologne, Germany

The collision between the Indian and Eurasian plates promotes the southeastward extrusion of the Indochina Peninsula while the internal dynamics of its crustal deformation remain enigmatic. Here, we make use of seismic data from 38 stations and employ the ambient noise tomography to construct a 3‐D crustal shear‐wave velocity (Vs) model beneath the Indochina Peninsula. A low‐Vs anomaly is revealed in the mid‐lower crust of the Shan‐Thai Block and probably corresponds to the southern extension of the crustal flow from SE Tibet. Although the Khorat Plateau behaves as a rigid block, the observed low‐Vs anomalies in the lower crust and also below the Moho indicate that the crust may have been partially modified by mantle‐derived melts. The strike‐slip shearing motions of the Red River Fault may have dominantly developed crustal deformation at its western flank where a low‐Vs anomaly is observed at the upper‐middle crust., Plain Language Summary: The Indochina Peninsula was believed to behave as a rigid block where significant southeastward extrusion and clockwise rotation have occurred in response to the collision between the Indian and Eurasian plates. Here, we employ ambient noise data to obtain the shear‐wave velocity (Vs) images and find deformations in the interior of the crust beneath the Indochina Peninsula. A low‐Vs anomaly is observed in the mid‐lower crust of the Shan‐Thai Block and represents the crustal flow from SE Tibet. The crust of the Khorat Plateau, the core of the Indochina Block, has been partially modified by mantle‐derived melts. The strike‐slip shearing motions of the Red River Fault have brought crustal deformation at its southwestern flank characterized as a low‐Vs anomaly in the upper‐middle crust., Key Points: A 3‐D crustal shear‐wave velocity (Vs) model was constructed for the Indochina Peninsula from ambient noise tomography. Low‐Vs in the middle‐lower crust of the Shan‐Thai Block may represent the southern extension of the crustal flow from SE Tibet. The crust of the rigid Khorat Plateau has been partially modified by intrusion of mantle‐derived melts., National Natural Science Foundation of China http://dx.doi.org/10.13039/501100001809, the State Key Laboratory of Marine Geology, Tongji University, Shanghai Sheshan National Geophysical Observatory, https://doi.org/10.5281/zenodo.5235658

Imaging the critical zone at depth, where intact bedrock transforms into regolith, is critical in understanding the interaction between geological and biological processes. We acquired a 500 m‐long near‐surface seismic profile to investigate the weathering structure in the Santa Gracia National Reserve, Chile, which is located in a granitic environment in an arid climate. Data processing comprised the combination of two seismic approaches: (1) body wave tomography and (2) multichannel analysis of surface wave (MASW) with Bayesian inversion. This allowed us to derive P‐wave and S‐wave velocity models down to 90 and 70 m depth, respectively. By calibrating the seismic results with those from an 87 m‐deep borehole that is crossed by the profile. We identified the boundaries of saprolite, weathered bedrock, and bedrock. These divisions are indicated in the seismic velocity variations and refer to weathering effects at depth. The thereby determined weathering front in the borehole location can be traced down to 30 m depth. The modelled lateral extent of the weathering front, however, cannot be described by an established weathering front model. The discrepancies suggest a more complex interaction between different aspects such as precipitation and topography in controlling the weathering front depth., Combined seismic approaches of body wave tomography and MASW method revealed the upper 90 m of the critical zone down to the bedrock. The integration of the borehole data with the resulting P‐ and S‐wave velocity model, as well as the vertical velocity gradient model, provides a strong constraint in identifying the different lithologies. The resulting conceptual model shows the extent of the critical zone in Santa Gracia Reserve, Chile and its relation to topography., German Science Foundation (DFG) priority research programme SPP‐1803 ‘EarthShape: Earth Surface Shaping by Biota’

Seismicity models are probabilistic forecasts of earthquake rates to support seismic hazard assessment. Physics‐based models allow extrapolating previously unsampled parameter ranges and enable conclusions on underlying tectonic or human‐induced processes. The Coulomb Failure (CF) and the rate‐and‐state (RS) models are two widely used physics‐based seismicity models both assuming pre‐existing populations of faults responding to Coulomb stress changes. The CF model depends on the absolute Coulomb stress and assumes instantaneous triggering if stress exceeds a threshold, while the RS model only depends on stress changes. Both models can predict background earthquake rates and time‐dependent stress effects, but the RS model with its three independent parameters can additionally explain delayed aftershock triggering. This study introduces a modified CF model where the instantaneous triggering is replaced by a mean time‐to‐failure depending on the absolute stress value. For the specific choice of an exponential dependence on stress and a stationary initial seismicity rate, we show that the model leads to identical results as the RS model and reproduces the Omori‐Utsu relation for aftershock decays as well stress‐shadowing effects. Thus, both CF and RS models can be seen as special cases of the new model. However, the new stress response model can also account for subcritical initial stress conditions and alternative functions of the mean time‐to‐failure depending on the problem and fracture mode., Plain Language Summary: One of the most pressing questions in earthquake physics is understanding where and when earthquakes occur and how seismicity is related to stress changes in the Earth's crust. This question is even more important today because humans are increasingly influencing stresses in the Earth by exploiting the subsurface. So far, two classes of physics‐based seismicity models have been used primarily. One assumes instantaneous earthquake occurrence when stress exceeds a threshold, and the other is based on the nucleation of earthquakes according to friction laws determined in the laboratory. Both models are very different in their approaches, have advantages and disadvantages, and are limited in their applicability. In this paper, we introduce a new concept of seismicity models, which is very simple and short to derive and combines the strengths of both previous models, as shown in various applications to human‐related seismicity. The forecasts of both traditional models turn out to be special cases of the new model., Key Points: We introduce a modified Coulomb Failure seismicity model in which a mean time‐to‐failure replaces instantaneous triggering. The model explains the main features of time‐dependent seismicity, including aftershock activity and stress shadow effects. As a special case, it includes the rate‐state model solutions but can also handle subcritical stresses and other fracture types., European Unions 2020 research and innovation programme, https://github.com/torstendahm/tdsr

About 10% of Europe's surface area is prone to rapid flooding of rivers confined in valleys. The devastating potential of such floods is exacerbated by the deficits of existing gauging networks, including low station densities and recording frequencies, and lack of information beyond stage height. Here, we use seismic data of the July 2021 Ahrtal flood, Germany, to extract information to complement sparse hydrometric data, and to reconstruct the rapid evolution of this fatal event. We show that a seismic station can deliver essential flood metrics such as magnitude, propagation velocity and debris transport rate. These seismic products provide high resolution insight to the non‐linear flood behavior. We argue that an approach combining distributed low‐cost seismometers with existing seismic stations, can provide important real time data on future catastrophic floods and associated hazards in upland catchments, offering precious response time also in currently ungauged landscapes., Plain Language Summary: Rapidly evolving floods are a major hazard for 10% of European landscapes. They are hard to adequately detect and describe by the classic gauge station scheme, but seismic sensors provide a valuable alternative to this difficulty. A seismometer can sense a flood like the devastating one that hit the Ahr valley, Germany, in July 2021 up to 1.5 km away. The seismic footprint of the flood allows to provide information on flood magnitude, velocity and trajectory at sub‐minute resolution and at near real time. We show how this new approach can be utilized for future flood protection., Key Points: Seismic sensing of valley confined floods improves classic detection approaches. Near‐real time information on flood magnitude, trajectory, and velocity. Gate keeper seismometer networks can improve flood risk management in Europe., GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam—GFZ German Research Centre for Geosciences http://dx.doi.org/10.13039/501100010956, German Research Foundation

Raman spectroscopy has been widely used in mineralogy and petrology for identifying mineral phases. Some recent applications of Raman spectroscopy involve measuring the residual pressure of mineral inclusions, such as quartz inclusions in garnet host, to recover the entrapment pressure condition during metamorphism. The crystallographic orientations of entrapped inclusions and host are important to know for the modelling of their elastic interaction. However, the analysis of tiny entrapped mineral inclusions using EBSD technique requires time consuming polishing. The crystallographic orientations can be measured using polarized Raman spectroscopy, as the intensities of Raman bands depend on the mutual orientation between the polarization direction of the laser and the crystallographic orientation of the crystal. In this study, the Raman polarizability tensor of quartz is first obtained and is used to fit arbitrary orientations of quartz grains. We have implemented two rotation methods: (1) sample rotation method, where the sample is rotated on a rotation stage, and (2) polarizer rotation method, where the polarization directions of the incident laser and the scattered Raman signal are parallel and can be rotated using a circular polarizer. The precision of the measured crystallographic orientation is systematically studied and is shown to be ca. 0.25 degrees using quartz wafers and quartz plates that are cut along known orientations. It is shown that the orientation of tiny mineral inclusions (ca. 2–5 μm) can be precisely determined and yield consistent results with EBSD., Alexander von Humboldt-Stiftung http://dx.doi.org/10.13039/100005156, Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, Freie Universität Berlin (1008)

The determination of the natural remanent magnetization (NRM) of archaeological features can be used for magnetic modelling, joining of shards, archaeomagnetic dating or the investigation of the firing–cooling–collapsing order of ancient buildings. The measurement of NRM is normally conducted on cylindrical or cubic samples in the laboratory. Nevertheless, archaeological finds should preferably not be destroyed, and laboratory instruments are high in costs. Therefore, we propose a lightweight and portable measurement set‐up including already available field magnetometers (preferably caesium magnetometers) in which the archaeological sample of arbitrary shape, in our case a piece of daub, is mounted inside a gimbal to be rotated in all directions. The magnetic field of the sample is measured at a large number of rotational positions with the magnetometer kept at fixed position. In these measurements, the unknown direction of the NRM vector of the sample is rotated, whereas the average magnetic susceptibility of the sample and the ambient magnetic field are constant and known. Hence, the vector of NRM can be determined through least‐squares inversion. For the inversion computation, the sample volume is discretized either as voxel model or approximated as an equivalent sphere. Under certain conditions depending on sample–sensor distance, dipole moment and radius of the sample, the approximation by a sphere is valid without effect on the accuracy of results. Empirically determined functions quantifying these conditions for different sensor sensitivities and noise levels are provided. Validation with laboratory measurements on palaeomagnetic subsamples from the destroyed daub samples indicate that the NRM can be determined by our proposed method with a maximum error in inclination of 2°, in declination of 20° and in magnetization of ±0.6 A/m. This is accurate enough, for example, to determine from daub pieces of burnt house remains whether the building was burnt and cooled before or after it collapsed., German Research Foundation http://dx.doi.org/10.13039/501100001659

The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission carries magnetometers that are dedicated to enhance the satellite’s navigation. After appropriate calibration and characterisation of artificial magnetic disturbances, these observations are valuable assets to characterise the natural variability of Earth’s magnetic field. We describe the data pre-processing, the calibration, and characterisation strategy against a high-precision magnetic field model applied to the GRACE-FO magnetic data. During times of geomagnetic quiet conditions, the mean residual to the magnetic model is around 1 nT with standard deviations below 10 nT. The mean difference to data of ESA’s Swarm mission, which is dedicated to monitor the Earth’s magnetic field, is mainly within ± 10 nT during conjunctions. The performance of GRACE-FO magnetic data is further discussed on selected scientific examples. During a magnetic storm event in August 2018, GRACE-FO reveals the local time dependence of the magnetospheric ring current signature, which is in good agreement with results from a network of ground magnetic observations. Also, derived field-aligned currents (FACs) are applied to monitor auroral FACs that compare well in amplitude and statistical behaviour for local time, hemisphere, and solar wind conditions to approved earlier findings from other missions including Swarm. On a case event, it is demonstrated that the dual-satellite constellation of GRACE-FO is most suitable to derive the persistence of auroral FACs with scale lengths of 180 km or longer. Due to a relatively larger noise level compared to dedicated magnetic missions, GRACE-FO is especially suitable for high-amplitude event studies. However, GRACE-FO is also sensitive to ionospheric signatures even below the noise level within statistical approaches. The combination with data of dedicated magnetic field missions and other missions carrying non-dedicated magnetometers greatly enhances related scientific perspectives., European Space Agency (FR), HEIBRIDS, Projekt DEAL, ftp://isdcftp.gfz-potsdam.de/grace-fo/MAGNETIC_FIELD

The use of the GLONASS legacy signals for real-time kinematic positioning is considered. Due to the FDMA multiplexing scheme, the conventional CDMA observation model has to be modified to restore the integer estimability of the ambiguities. This modification has a strong impact on positioning capabilities. In particular, the ambiguity resolution performance of this model is clearly weaker than for CDMA systems, so that fast and reliable full ambiguity resolution is usually not feasible for standalone GLONASS, and adding GLONASS data in a multi-GNSS approach can reduce the ambiguity resolution performance of the combined model. Partial ambiguity resolution was demonstrated to be a suitable tool to overcome this weakness (Teunissen in GPS Solut 23(4):100, 2019). We provide an exhaustive formal analysis of the positioning precision and ambiguity resolution capabilities for short, medium, and long baselines in a multi-GNSS environment with GPS, Galileo, BeiDou, QZSS, and GLONASS. Simulations are used to show that with a difference test-based partial ambiguity resolution method, adding GLONASS data improves the positioning performance in all considered cases. Real data from different baselines are used to verify these findings. When using all five available systems, instantaneous centimeter-level positioning is possible on an 88.5 km baseline with the ionosphere weighted model, and on average, only 3.27 epochs are required for a long baseline with the ionosphere float model, thereby enabling near instantaneous solutions., Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ (4217), https://saegnss2.curtin.edu/ldc/, ftp://cddis.gsfc.nasa.gov/gnss/data/, ftp://ftp.gfz-potsdam.de/GNSS/products/mgex/

The Niederschlag fluorite-barite vein deposit in the Western Erzgebirge, Germany, has been actively mined since 2013. We present the results of a first comprehensive study of the mineralogy, petrography, fluid inclusions, and trace element geochemistry of fluorite related to the Niederschlag deposit. Two different stages of fluorite mineralization are recognized. Stage I fluorite is older, fine-grained, associated with quartz, and forms complex breccia and replacement textures. Conversely, the younger Stage II fluorite is accompanied by barite and often occurs as banded and coarse crystalline open-space infill. Fluid inclusion and REY systematics are distinctly different for these two fluorite stages. Fluid inclusions in fluorite I reveal the presence of a low to medium saline (7–20% eq. w (NaCl+CaCl2)) fluid with homogenization temperatures of 140–180 °C, whereas fluorite II inclusions yield distinctly lower (80–120 °C) homogenization temperatures with at least two high salinity fluids involved (18–27% eq. w (NaCl+CaCl2)). In the absence of geochronological data, the genesis of the earlier generation of fluorite-quartz mineralization remains enigmatic but is tentatively related to Permian magmatism in the Erzgebirge. The younger fluorite-barite mineralization, on the other hand, has similarities to many fluorite-barite-Pb-Zn-Cu vein deposits in Europe that are widely accepted to be related to the Mesozoic opening of the northern Atlantic Ocean., European Social Fund http://dx.doi.org/10.13039/501100004895

Much of contemporary landslide research is concerned with predicting and mapping susceptibility to slope failure. Many studies rely on generalised linear models with environmental predictors that are trained with data collected from within and outside of the margins of mapped landslides. Whether and how the performance of these models depends on sample size, location, or time remains largely untested. We address this question by exploring the sensitivity of a multivariate logistic regression—one of the most widely used susceptibility models—to data sampled from different portions of landslides in two independent inventories (i.e. a historic and a multi-temporal) covering parts of the eastern rim of the Fergana Basin, Kyrgyzstan. We find that considering only areas on lower parts of landslides, and hence most likely their deposits, can improve the model performance by >10% over the reference case that uses the entire landslide areas, especially for landslides of intermediate size. Hence, using landslide toe areas may suffice for this particular model and come in useful where landslide scars are vague or hidden in this part of Central Asia. The model performance marginally varied after progressively updating and adding more landslides data through time. We conclude that landslide susceptibility estimates for the study area remain largely insensitive to changes in data over about a decade. Spatial or temporal stratified sampling contributes only minor variations to model performance. Our findings call for more extensive testing of the concept of dynamic susceptibility and its interpretation in data-driven models, especially within the broader framework of landslide risk assessment under environmental and land-use change., Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347

Knowledge of pressure-dependent static and dynamic moduli of porous reservoir rocks is of key importance for evaluating geological setting of a reservoir in geo-energy applications. We examined experimentally the evolution of static and dynamic bulk moduli for porous Bentheim sandstone with increasing confining pressure up to about 190 MPa under dry and water-saturated conditions. The static bulk moduli (Ks) were estimated from stress–volumetric strain curves while dynamic bulk moduli (Kd) were derived from the changes in ultrasonic P- and S- wave velocities (~ 1 MHz) along different traces, which were monitored simultaneously during the entire deformation. In conjunction with published data of other porous sandstones (Berea, Navajo and Weber sandstones), our results reveal that the ratio between dynamic and static bulk moduli (Kd/Ks) reduces rapidly from about 1.5 − 2.0 at ambient pressure to about 1.1 at high pressure under dry conditions and from about 2.0 − 4.0 to about 1.5 under water-saturated conditions, respectively. We interpret such a pressure-dependent reduction by closure of narrow (compliant) cracks, highlighting that Kd/Ks is positively correlated with the amount of narrow cracks. Above the crack closure pressure, where equant (stiff) pores dominate the void space, Kd/Ks is almost constant. The enhanced difference between dynamic and static bulk moduli under water saturation compared to dry conditions is possibly caused by high pore pressure that is locally maintained if measured using high-frequency ultrasonic wave velocities. In our experiments, the pressure dependence of dynamic bulk modulus of water-saturated Bentheim sandstone at effective pressures above 5 MPa can be roughly predicted by both the effective medium theory (Mori–Tanaka scheme) and the squirt-flow model. Static bulk moduli are found to be more sensitive to narrow cracks than dynamic bulk moduli for porous sandstones under dry and water-saturated conditions., Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ (4217)

Situated in the western Erzgebirge metallogenetic province (Vogtland, Germany), the Eichigt prospect is associated with several quartz-Mn-Fe-oxyhydroxide veins that are exposed at surface. Bulk-rock geochemical assays of vein material yield high concentrations of Li (0.6–4.1 kg/t), Co (0.6–14.7 kg/t), and Ni (0.2–2.8 kg/t), as well as significant quantities of Mn, Cu, and light rare earth elements, a very unusual metal tenor closely resembling the mixture of raw materials needed for Li-ion battery production. This study reports on the results of a first detailed investigation of this rather unique polymetallic mineralization style, including detailed petrographic and mineralogical studies complemented by bulk rock geochemistry, electron microprobe analyses, and laser ablation inductively coupled mass spectrometry. The mineralized material comprises an oxide assemblage of goethite hematite, hollandite, and lithiophorite that together cement angular fragments of vein quartz. Lithiophorite is the predominant host of Li (3.6–11.1 kg/t), Co (2.5–54.5 kg/t), and Ni (0.2–8.9 kg/t); Cu is contained in similar amounts in hollandite and lithiophorite whereas light rare earth elements (LREE) are mainly hosted in microcrystalline rhabdophane and florencite, which are finely intergrown with the Mn-Fe-oxyhydroxides. 40Ar/39Ar ages (~ 40–34 Ma) of coronadite group minerals coincide with tectonic activity related to the Cenozoic Eger Graben rifting. A low-temperature hydrothermal overprint of pre-existing base metal sulfide-quartz mineralization on fault structures that were reactivated during continental rifting is proposed as the most likely origin of the polymetallic oxyhydroxide mineralization at Eichigt. However, tectonically enhanced deep-reaching fracture-controlled supergene weathering cannot be completely ruled out as the origin of the mineralization., Lithium Australia, European Social Fund http://dx.doi.org/10.13039/501100004895, Technische Universität Bergakademie Freiberg (3135)

The simulation of broad-band (0.1 to 10 + Hz) ground-shaking over deep and spatially extended sedimentary basins at regional scales is challenging. We evaluate the ground-shaking of a potential M 6.5 earthquake in the southern Lower Rhine Embayment, one of the most important areas of earthquake recurrence north of the Alps, close to the city of Cologne in Germany. In a first step, information from geological investigations, seismic experiments and boreholes is combined for deriving a harmonized 3D velocity and attenuation model of the sedimentary layers. Three alternative approaches are then applied and compared to evaluate the impact of the sedimentary cover on ground-motion amplification. The first approach builds on existing response spectra ground-motion models whose amplification factors empirically take into account the influence of the sedimentary layers through a standard parameterization. In the second approach, site-specific 1D amplification functions are computed from the 3D basin model. Using a random vibration theory approach, we adjust the empirical response spectra predicted for soft rock conditions by local site amplification factors: amplifications and associated ground-motions are predicted both in the Fourier and in the response spectra domain. In the third approach, hybrid physics-based ground-motion simulations are used to predict time histories for soft rock conditions which are subsequently modified using the 1D site-specific amplification functions computed in method 2. For large distances and at short periods, the differences between the three approaches become less notable due to the significant attenuation of the sedimentary layers. At intermediate and long periods, generic empirical ground-motion models provide lower levels of amplification from sedimentary soils compared to methods taking into account site-specific 1D amplification functions. In the near-source region, hybrid physics-based ground-motions models illustrate the potentially large variability of ground-motion due to finite source effects., Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ (4217)

In this study, we have derived field-aligned currents (FACs) from magnetometers onboard the Defense Meteorological Satellite Project (DMSP) satellites. The magnetic latitude versus local time distribution of FACs from DMSP shows comparable dependences with previous findings on the intensity and orientation of interplanetary magnetic field (IMF) By and Bz components, which confirms the reliability of DMSP FAC data set. With simultaneous measurements of precipitating particles from DMSP, we further investigate the relation between large-scale FACs and precipitating particles. Our result shows that precipitation electron and ion fluxes both increase in magnitude and extend to lower latitude for enhanced southward IMF Bz, which is similar to the behavior of FACs. Under weak northward and southward Bz conditions, the locations of the R2 current maxima, at both dusk and dawn sides and in both hemispheres, are found to be close to the maxima of the particle energy fluxes; while for the same IMF conditions, R1 currents are displaced further to the respective particle flux peaks. Largest displacement (about 3.5°) is found between the downward R1 current and ion flux peak at the dawn side. Our results suggest that there exists systematic differences in locations of electron/ion precipitation and large-scale upward/downward FACs. As outlined by the statistical mean of these two parameters, the FAC peaks enclose the particle energy flux peaks in an auroral band at both dusk and dawn sides. Our comparisons also found that particle precipitation at dawn and dusk and in both hemispheres maximizes near the mean R2 current peaks. The particle precipitation flux maxima closer to the R1 current peaks are lower in magnitude. This is opposite to the known feature that R1 currents are on average stronger than R2 currents., European Space Agency http://dx.doi.org/10.13039/501100000844, Swarm DISC, German Research Foundation, Projekt DEAL

Regions of low seismicity present a particular challenge for probabilistic seismic hazard analysis when identifying suitable ground motion models (GMMs) and quantifying their epistemic uncertainty. The 2020 European Seismic Hazard Model adopts a scaled backbone approach to characterise this uncertainty for shallow seismicity in Europe, incorporating region-to-region source and attenuation variability based on European strong motion data. This approach, however, may not be suited to stable cratonic region of northeastern Europe (encompassing Finland, Sweden and the Baltic countries), where exploration of various global geophysical datasets reveals that its crustal properties are distinctly different from the rest of Europe, and are instead more closely represented by those of the Central and Eastern United States. Building upon the suite of models developed by the recent NGA East project, we construct a new scaled backbone ground motion model and calibrate its corresponding epistemic uncertainties. The resulting logic tree is shown to provide comparable hazard outcomes to the epistemic uncertainty modelling strategy adopted for the Eastern United States, despite the different approaches taken. Comparison with previous GMM selections for northeastern Europe, however, highlights key differences in short period accelerations resulting from new assumptions regarding the characteristics of the reference rock and its influence on site amplification., Horizon 2020 Framework Programme http://dx.doi.org/10.13039/100010661, Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ (4217)

To complement the new European Strong-Motion dataset and the ongoing efforts to update the seismic hazard and risk assessment of Europe and Mediterranean regions, we propose a new regionally adaptable ground-motion model (GMM). We present here the GMM capable of predicting the 5% damped RotD50 of PGA, PGV, and SA(T = 0.01 − 8 s) from shallow crustal earthquakes of 3 ≤ M W ≤ 7.4 occurring 0 < RJB ≤ 545 km away from sites with 90 ≤ Vs30 ≤ 3000 m s−1 or 0.001 ≤ slope ≤ 1 m m−1. The extended applicability derived from thousands of new recordings, however, comes with an apparent increase in the aleatory variability (σ). Firstly, anticipating contaminations and peculiarities in the dataset, we employed robust mixed-effect regressions to down weigh only, and not elimi nate entirely, the influence of outliers on the GMM median and σ. Secondly, we regionalised the attenuating path and localised the earthquake sources using the most recent models, to quantify region-specific anelastic attenuation and locality-specific earthquake characteristics as random-effects, respectively. Thirdly, using the mixed-effect variance–covariance structure, the GMM can be adapted to new regions, localities, and sites with specific datasets. Consequently, the σ is curtailed to a 7% increase at T < 0.3 s, and a sub stantial 15% decrease at T ≥ 0.3 s, compared to the RESORCE based partially non-ergodic GMM. We provide the 46 attenuating region-, 56 earthquake localities-, and 1829 site-spe cific adjustments, demonstrate their usage, and present their robustness through a 10-fold cross-validation exercise., SIGMA2 consortium (EDF, CEA, PG&E, SwissNuclear,. Areva, CEZ, CRIEPI), H2020 Research Infrastructures http://dx.doi.org/10.13039/100010666

Groningen is the largest onshore gas field under production in Europe. The pressure depletion of the gas field started in 1963. In 1991, the first induced micro-earthquakes have been located at reservoir level with increasing rates in the following decades. Most of these events are of magnitude less than 2.0 and cannot be felt. However, maximum observed magnitudes continuously increased over the years until the largest, significant event with ML=3.6 was recorded in 2014, which finally led to the decision to reduce the production. This causal sequence displays the crucial role of understanding and modeling the relation between production and induced seismicity for economic planing and hazard assessment. Here we test whether the induced seismicity related to gas exploration can be modeled by the statistical response of fault networks with rate-and-state-dependent frictional behavior. We use the long and complete local seismic catalog and additionally detailed information on production-induced changes at the reservoir level to test different seismicity models. Both the changes of the fluid pressure and of the reservoir compaction are tested as input to approximate the Coulomb stress changes. We find that the rate-and-state model with a constant tectonic background seismicity rate can reproduce the observed long delay of the seismicity onset. In contrast, so-called Coulomb failure models with instantaneous earthquake nucleation need to assume that all faults are initially far from a critical state of stress to explain the delay. Our rate-and-state model based on the fluid pore pressure fits the spatiotemporal pattern of the seismicity best, where the fit further improves by taking the fault density and orientation into account. Despite its simplicity with only three free parameters, the rate-and-state model can reproduce the main statistical features of the observed activity., Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347, Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659

Tree roots penetrate the soil to several meters depth, but the role of subsoils for the supply of nutrient elements such as phosphorus (P) to the trees is poorly understood. Here, we tested the hypothesis that increased P deficiency in the topsoil results in an increased microbial recycling of P from the forest subsoil. We sampled soils from four German temperate forest sites representing a gradient in total P stocks. We analyzed the oxygen isotopic composition of HCl-extractable phosphate (δ18OP) and identified differences in P speciation with increasing soil depth using X-ray absorption near-edge structure (XANES) spectroscopy. We further determined microbial oxygen demand with and without nutrient supply at different soil depths to analyse nutrient limitation of microbial growth and used nanoscale secondary ion mass spectrometry (NanoSIMS) to visualize spatial P gradients in the rhizosphere. We found that δ18OP values in the topsoil of all sites were close to the isotopic signal imparted by biological cycling when oxygen isotopes in phosphate are exchanged by enzymatic activity. However, with increasing soil depth and increasing HCl-P concentrations, δ18Ο values continuously decreased towards values expected for primary minerals in parent material at depths below 60 cm at sites with high subsoil P stocks and below more than 2 m at sites with low subsoil P stocks, respectively. For these depths, XANES spectra also indicated the presence of apatite. NanoSIMS images showed an enrichment of P in the rhizosphere in the topsoil of a site with high P stocks, while this P enrichment was absent at a site with low P stocks and in both subsoils. Addition of C, N and P alone or in combination revealed that microbial activity in subsoils of sites with low P stocks was mostly P limited, whereas sites with high P stocks indicated N limitation or N and P co-limitation. We conclude that subsoil P resources are recycled by trees and soil microorganisms. With continued weathering of the bedrock and mobilisation of P from the weathered rocks, P cycling will proceed to greater depths, especially at sites characterised by P limitation., Biogeochemistry, 150 (3), ISSN:0168-2563, ISSN:1573-515X