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In this contribution, we show first results of repeat-pass interferometric measurements of glacier flow velocity obtained in fall 2018 with Gamma Remote Sensing's novel GS-L system, a compact synthetic aperture radar system at L-band. In this experiment, the GS-L SAR system was operated in a car-borne mode so that mobile mapping of a glacier and its surroundings could be performed from a road. Several repeat-pass SAR acquisitions where taken along a slightly curved road section on the "Susten" mountain pass, in central Switzerland, from which substantial parts of the "Steingletscher" glacier can be imaged.The carborne SAR data was focused along a synthetic aperture of approx. 250m using a time-domain back-projection (TDBP) approach and the data was focused directly to a reconstruction grid in map coordinates [1,2].A CUDA/ ANSI C implementation of the TDBP focusing was used to focus the data as described in our previous Ku-band carborne SAR test cases [3-6]. The TDBP-processing to map coordinates --- involving an accurate digital elevation model --- allows to directly form differential interferograms in map coordinates.A highly-precise navigation-grade ring-laser-gyro INS/GNSS system with a local GNSS reference station was used for positioning and attitude determination of the SAR system so that the azimuth-varying baselines (due to the repeated slightly different driving paths on the road) are well-known and the topography induced phase can be directly removed to a large extent by means of the TDBP-based focusing procedure.In the context of the DInSAR-based estimation of glacier flow velocity that is presented we discuss aspects such as mitigation of troposphere-induced phase contributions and residual motion-induced phases, as well as interferometric stacking of the time-series of carborne repeat-pass measurements.References:[1] O. Frey and C. Magnard and M. Ruegg and E. Meier, "Focusing of Airborne Synthetic Aperture Radar Data from Highly Nonlinear Flight Tracks," IEEE Trans. Geosci. Remote Sens., vol. 47, no. 6, pp. 1844–1858, 2009 [Online]. Available: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4812049[2] O. Frey, E. Meier, and D. Nuesch, "Processing SAR data of rugged terrain by time-domain back-projection," in SPIE Vol. 5980: SAR Image Analysis, Modeling, and Techniques X, 2005. [3] O. Frey, C. L. Werner, U. Wegmuller, A. Wiesmann, D. Henke, and C. Magnard, "A car-borne SAR and InSAR experiment," in Proc. IEEE Int. Geosci. Remote Sens. Symp., 2013, pp. 93–96 [Online]. Available: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6721100[4] O. Frey, C. L. Werner, and U. Wegmuller, "GPU-based parallelized time-domain back-projection processing for agile SAR platforms," in Proc. IEEE Int. Geosci. Remote Sens. Symp., 2014, pp. 1132–1135.[5] O. Frey, C. L. Werner, I. Hajnsek, and R. Coscione, "A car-borne SAR system for interferometric measurements: development status and system enhancements," in Proc. IEEE Int. Geosci. Remote Sens. Symp., 2018, pp. 6508–6511. [6] R. Coscione, I. Hajnsek, and O. Frey, "An experimental car-borne SAR System: measurement setup and positioning error analysis," in Proc. IEEE Int. Geosci. Remote Sens. Symp., 2018, pp. 6364–6367. [ABSTRACT FROM AUTHOR]

In the year 1997, the Swiss Geophysical Commission (SGPK) launched the project Seismotectonic Atlas of Switzerland with the goal of a first nationwide inventory of seismotectonic relevant data. In the course of the project, the contribution of the Swiss Seismological Service (SED) focused on the calculation of earthquake focal mechanisms, the identification of stress regimes from stress inversions and possible ways to present the information on digital maps. Another goal of the project was the compilation of a map of active faults within the Swiss Alps from geological field data. The latter task, however, turned out to be challenging due to a lack of field-based evidence for recent fault activity and therefore only a handful of clearly active (i.e. neotectonic) faults could be mapped. Hence, large uncertainties regarding the seismotectonic interpretation remained.With the advances in earthquake monitoring and processing (e.g. improved data quality, significant densification of the seismic network, improved seismic velocity models, and relative relocation techniques), accuracy and precision of hypocenters improved significantly, so that today, location uncertainties can be narrowed down to the subkilometer scale (e.g. Diehl et al. 2017). In addition, recent re-processed and re-interpreted 2D and new high-resolution 2D and 3D reflection seismic data as well as geological 3D models provide new insights into the subsurface structural setting of the Swiss Molasse Basin (Heuberger et al. 2016; e.g. Landesgeologie 2017; Sommaruga et al. 2012). Furthermore, with swisstopo's harmonization of geological vector data (GeoCover) a more complete structural dataset becomes available. Insofar, the interplay between seismicity and faults can now be investigated in much more detail. Finally, the Global Navigation Satellite System (GNSS) in Switzerland provides increasing data volumes, leading to steady improvements of surface deformation estimates in the Alps and its foreland. In the light of these new developments, the SGPK has launched a follow-up project called 'SeismoTeCH' (Seismotectonic Characterization of Switzerland). In the corresponding pilot study presented here, we try to highlight different aspects and possibilities of seismotectonic interpretation, but also the pitfalls associated with it. Furthermore, we try to establish a strategic roadmap for the development of a future seismotectonic model of Switzerland.References:Diehl, T., Kraft, T., Kissling, E., & Wiemer, S. (2017). The induced earthquake sequence related to the St. Gallen deep geothermal project (Switzerland): Fault reactivation and fluid interactions imaged by microseismicity. Journal of Geophysical Research: Solid Earth, 122(9), 7272ñ7290. doi:10.1002/2017JB014473Heuberger, S., Roth, P., Zingg, O., Naef, H., & Meier, B. P. (2016). The St. Gallen Fault Zone: a long-lived, multiphase structure in the North Alpine Foreland Basin revealed by 3D seismic data. Swiss Journal of Geosciences, 109(1), 83ñ102. doi:10.1007/s00015-016-0208-5Landesgeologie. (2017). GeoMol: Geologisches 3D-Modell des Schweizer Molassebeckens - Schlussbericht. Berichte der Landesgeologie, 10, 128 pp.Sommaruga, A., Eichenberger, U., & Marillier, F. (2012). Seismic Atlas of the Swiss Molasse Basin. MatÈriaux pour la GÈologie de la Suisse - GÈophysique, (44). [ABSTRACT FROM AUTHOR]

The ETRS89 was defined and introduced by EUREF in the early nineties, so some thirtyyears ago, for positioning applications, but also for unifying Pan-European nationalreference frames. By definition, the ETRS89 and ITRS are intimately linked by a 14-parametersimilarity transformation, in such a way that the ETRS89 horizontal station velocities areminimized in order to accommodate centimetric operational geodetic applications in Europe.However, as both systems coincide together at epoch 1989.0, the ETRS89 realizations divergefrom the ITRS by about 60 cm today.Given the development and improvement of fast, easy-to-use, and highly accurate tools and methodsof precise point positioning, making use of IGS GNSS orbits that are aligned to the ITRS, the questionthat arrises is weather we still need to use the ETRS89 in Europe ? The paper will address the prosand cons of the ETRS89 from the user perspectives. [ABSTRACT FROM AUTHOR]

Understanding the initial and flow conditions of contemporary flows in Martian gullies, generally believed to be triggered and fluidized by CO2 sublimation, is crucial for deciphering climate conditions needed to trigger and sustain them. We employ the RAMMS (RApid Mass Movement Simulation) debris flow and avalanche model to back-calculate initial and flow conditions of recent flows in three gullies in Hale crater. We infer minimum release depths of 1.0-1.5 m and initial release volumes of 100-200 m3. Entrainment leads to final flow volumes that are ~2.5-5.5 times larger than initially released, and entrainment is found necessary to match the observed flow deposits. Simulated mean cross-channel flow velocities decrease from 3-4 m s-1 to ~1 m s-1 from release area to flow terminus, while flow depths generally decrease from 0.5-1 m to 0.1-0.2 m. The mean cross-channel erosion depth and deposition thicknesses are ~0.1-0.3 m. Back-calculated dry-Coulomb friction ranges from 0.1 to 0.25 and viscous-turbulent friction between 100-200 m s-2, which are values similar to those of granular debris flows on Earth. These results suggest that recent flows in gullies are fluidized to a similar degree as are granular debris flows on Earth. Using a novel model for mass-flow fluidization by CO2 sublimation we are able to show that under Martian atmospheric conditions very small volumetric fractions of CO2 of <<1% within mass flows may indeed yield sufficiently large gas fluxes to cause fluidization and enhance flow mobility. [ABSTRACT FROM AUTHOR]

Pohang earthquake(moment magnitude 5.4) happened in November 15, 2017. 9 short period stations were installed and vertical green function was calculated from ambient noise before and after earthquake using deconvolution method. 6 short period stations were installed additionally after Pohang earthquake. Surface wave of vertical green function derived from ambient noise after earthquake arrived later than that before earthquake. We calculated velocity structure from dispersion curve of green function derived from ambient noise. Also we applied travel time tomography using aftershocks of Pohang earthquake. results from two methods showed the structure of Heunghae basin well. 3D velocity structure was applied to improve locations of aftershocks. [ABSTRACT FROM AUTHOR]

Serpentinization of mantle-derived peridotites at mid-ocean ridges occurs in slow spreading rate contexts, next to large-offset axial normal faults (detachment faults) that bring these mantle-derived rocks into the upper lithosphere. In this context, serpentinization contributes to the formation of a 2 to 5 km-thick geophysically-defined crustal layer. Based on an overview of mostly published geological, petrological and geophysical constraints, we address the tectonic and magmatic controls on mid-ocean ridge serpentinization, and on its spatial distribution. Microstructural, mineralogical and oxygen isotope studies indicate that mid-ocean ridge serpentinization involves an initial stage of formation of a serpentine mesh texture under low fluid-rock ratio conditions, followed by several stages of higher fluid-rock ratio veining and recrystallization of the initial serpentine, all occurring for the most part at relatively high temperatures (200-350°C), within the range that is most kinetically favorable for olivine serpentinization. Microcracks that are used as pathways for hydrothermal fluids at the mesh texture formation stage are tightly-spaced (< a few hundred microns) and kinetic constraints indicate that this stage probably occurs within a few years of hydrothermal fluids gaining access to the peridotite. This leads to a conceptual model of mesh texture formation in the axial ultramafic basement in and next to axial detachment fault zones, at temperatures in the 200-350°C range, and in association with weak hydrothermal circulation. Seismicity constraints suggest that this may occur at depths of as much as 15km below seafloor at very slow spreading ridges. Yet, gravity and seismic velocity constraints are not consistent with large volumes of serpentinized mantle at such depths, suggesting that this type of serpentinization is restricted to the fault's damage zone. Lower temperature serpentinization also probably occurs (at slower rates) at shallower, crustal depths, in tectonically damaged domains farther away from the fault, although we lack the samples to check this. Finally, episodes of extensive serpentinization involving black-smoker type fluids occur locally in domains of the tectonically damaged ultramafic basement that channel vigorous hydrothermal cells cooling magmatic intrusions. These three modes of serpentinization are expected to combine in detachment-dominated ridge regions to create an upper lithosphere layer made of partially serpentinized peridotites and isolated gabbroic bodies, with crustal-type seismic velocities and densities. [ABSTRACT FROM AUTHOR]

The rupture directivity causes variations in the ground motion at different source azimuths.Rupture directivity was estimated for the 2016 Gyeongju earthquake (Mw 5.5), its foreshock(Mw 5.1), and 22 aftershocks (Mw ≥ 3.0) using relative peak ground velocity (PGV)changes. The PGVs were estimated using velocity data recorded at the regional seismographnetworks administered by Korea Meteorological Administration and Korea Institute ofGeoscience and Mineral Resources, and at the temporary aftershock monitoring network.Epicentral distance was limited with 120 km to prevent the effect that the post-critical Mohoreflections (SmS) governs the peak amplitude of waveform. The Boatwright&#x2019;s method,in which the rupture directivity function could be estimated based on the relativepeak ground motions of seismic stations, was applied for station correction andinversion of rupture directivity. The fault rupture direction was estimated by usingBen-Menahem&#x2019;s directivity function. The inversion results were compared with focalmechanisms for each earthquake and with aftershocks distribution pattern. The resultsshow that the foreshock (Mw 5.1) and mainshock (Mw 5.5) have opposite rupturedirectivity and both directions are well correlated with the aftershock distribution. Thefault plane solution and rupture directions estimated in this study show that thesubparallel multiple ruptures are responsible for the 2016 Gyeongju earthquake sequence. [ABSTRACT FROM AUTHOR]

We present a comprehensive study of Rayleigh wave group velocity tomography in SouthIndia. South India is a stable continent comprising of Precambrian terrains such as the easternDharwar craton (EDC), the western Dharwar craton (WDC), the southern Granulite terrain(SGT), and the Cuddapah basin. The data used for analysis were recorded at 51 broadbandstations operated during 2009-2012 across this region. Based on the analysis a total of781 unique earthquake events with shallow to moderate depths were chosen. Theepicentral distance was from 5o-30o and magnitude Ms &#x003E;= 4.5. This attributedto a total of 4873 source-station raypaths for which the dispersion curves werecalculated to obtain Rayleigh-wave group velocity maps for time periods from10-200 secs. Due to the high ray coverage over the southern terrain, we obtained ahigh resolution of 0.5o-1o across all time periods. The tomographic velocity mapsshow a thinner crust (∼35 Km) in the late Archean (∼2.7 Ga) EDC and relativelyhigher (∼40-50 Km) in adjoining terrains (mid-Archean and Proterozoic). Themid-Archean (∼3.36 Ga) WDC has a thicker crust (∼50 Km). Furthermore, the local groupvelocity dispersion curve obtained for each grid cell from 10-200 seconds wereinverted for shear wave velocity models. The shear wave velocity models gave aquantitative image of the crust as well as the lithospheric root. The mid-ArcheanWDC has a thicker lithosphere with lithosphere-asthenosphere(LAB) around anaverage of 160-180 Km. The southern root of the lithosphere of WDC continued tillnorthern province of SGT which showed higher LAB compared to the thickness in therest of SGT (∼140 Km). The LAB in late Archean EDC along with the Cuddapahprovince was found to be flat and thinner (∼140-160 Km) compared to WDC. Thecoastal areas showed a thin LAB (∼110-130 Km) except in the WDC boundary. Thesouthernmost tip showed a very thin LAB (100-110 Km). This observation suggests thatthe average crustal and lithospheric thickness of WDC is more compared to theEDC. This can infer that the WDC after it&#x2019;s cratonization has remained mostlyinert, while EDC might have undergone tectonothermal changes in the Proterozoic. [ABSTRACT FROM AUTHOR]

Local seismicity in geothermal fields is generally associated with perturbations of the pore pressure because of injection tests or fluid circulation during power plant operation. Besides, many geothermal regions are also prone to earthquake triggering as a result of transient stress variations caused by surface waves originated by strong regional earthquakes. To investigate possible changes in the seismicity rate in geothermal fields during and after the occurrence of regional strong earthquakes, we have analyzed seismic records following strong earthquakes (Mw>7) that have been acquired in the Los Humeros Caldera, Mexico. In the framework of the GEMEX project (cooperation between Europe and Mexico for geothermal development), a dense network of 45 stations was installed in 2017/2018 in this caldera that hosts one of the largest geothermal power plants of the country. Thanks to this network an intense local seismic activity has been recorded in the geothermal field, from which it has been possible to identify high frequency events (VT, >10 Hz) and low frequency seismicity (LP, 1-8 Hz). The two sets of events have been spatially correlated with 3D seismic velocity models of the region in order to better characterize the structure of the geothermal field and identify regions where the fluids could have a role on the triggering of the observed seismicity. This work is supported by the project GeMEX PT5.2.N: 267084 funded by CONACyT-SENER: S0019, 2015-04. [ABSTRACT FROM AUTHOR]

The influence of riparian vegetation on ecological and flow process in channels has become an increasingly important aspect of river flood risk and environmental management. Previous studies mainly focused on vegetation with the same height in either submerged or emergent condition which is not as real as natural rivers and channels. It happened while most of the rivers and natural channels consisted of different height of vegetation and experienced both emergent and submerged condition together. Therefore, understanding the hydrodynamics of flow in vegetated open channels with different types of vegetation and formations would provide valuable scientific means to evaluate the effect of vegetation on open channel flows. This study investigate the effect of different types and configuration of vegetation on the flow characteristics in open channels. Cylindrical cylinders with 6.35 mm diameter and two different heights of 10 cm and 20 cm which represent short and tall dowels respectively, have been planted in 10 mm thickness plates in staggered and linear formations to simulate the vegetation in both submerged and emergent condition. Different flow depths have been selected to cover all different submergence ration. The results reveal that the velocity profile is mostly uniform over the depth in different configurations, except at region behind the tall dowel. The increase of velocity profile above the short vegetation in three layers vegetation condition is much larger than that in two layers condition. Generally, in both cases the flow velocity inside the vegetation layer is significantly smaller than that in the surface layer (i.e. non-vegetation layer). A near-constant velocity dominates inside the vegetation layer, and then starts to increase near the interface at the top of vegetation. There is a sudden change in the shape of the velocity profile near the top edge of vegetation. The results also showed that for both two and three layers cases, the flow velocity is strongly dependent on locations, and that the distributions of the turbulent intensity attains maximum just around the edge of vegetation height. The same sets of vegetation configurations have also been simulated using K-e model with grid dependence analysis to capture the inflection over the short vegetation region. The simulated results are finally corroborated with experimental data and found to work satisfactorily for the present set of experiments. [ABSTRACT FROM AUTHOR]

Massive datasets can be used to examine geophysical phenomena in more detail than ever before but require analytical methods that are both efficient and capable of extracting useful information from faint signals immersed in noise. We have developed the AELUMA (Automated Event Location Using a Mesh of Arrays) method, which recasts any dense network of sensors as a distributed mesh of triangular arrays. Each array provides a local estimate of signal properties such as propagation direction, phase velocity and time of arrival. Machine learning techniques are used to combine signal characteristics observed at arrays across the network to estimate the origin time and location of the source. An advantage of this method is that little information about the propagation medium is required.The AELUMA method has been highly successful at detecting a variety of geophysical phenomena recorded at the USArray Transportable Array (TA) such as gravity wave signals excited by convective storms, faint gravity waves associated with the solar terminator, both natural and anthropogenic infrasound and seismic sources. This method is applicable to networks that are sufficiently dense such that signals, or their envelopes, may be correlated between adjacent stations, but does not require the signal to be observable across the entire network. Here we report on preliminary work on extending AELUMA to data from very sparse networks, including global scale networks. [ABSTRACT FROM AUTHOR]

The upper portion of oceanic crust is extremely difficult to image using conventional seismic imaging methods due to its complex internal structure and scattering of seismic energy on rough seafloor or basement topography. Recent advances in seismic data processing allow us to build high-resolution velocity models of the upper oceanic crust that can provide us with clues on physical properties and seismic structure. We perform acoustic full-waveform inversion of long-offset streamer data to explore the seismic velocity structure at the Mid-Atlantic Ridge (MAR) both on and off-axis. The results will build upon previous work revealing the regional seismic velocity distribution of 0-71 Ma upper oceanic crust at 31°S, between the MAR and the Rio Grande Rise. Two important issues that will be addressed are the nature of the seismic layer 2A/2B boundary and the spatial distribution of faults, which may give clues on the geometry of hydrothermal circulation. [ABSTRACT FROM AUTHOR]

Hydrometeor fall velocity is a critical parameterized variable in cloud microphysics schemes to control diffusive and coagulation growth, as well as gravitational settling and fallout of hydrometeors in numerical weather and climate models. An accurate parameterization of fall velocity is essential for accurate simulation of precipitation amounts and characteristics of clouds. Despite previous progress over the recent decades, large uncertainties still remain in the parameterization of fall velocity. We will report on a study in which the impact of uncertaintiesin fall velocity parameterization for frozen hydrometeors on an idealized squall line development is revisited from the perspective of hydrometeor population dynamics. We will show that for large precipitating frozen hydrometeors (i.e., snow/graupel/hail), the impact of the uncertaintiesvarieswith the size of precipitating hydrometeors whichis determined not only by the assumed size-mass and size-number-concentration relations, but also by the parameterized process rates. For example, results from the sensitivity experiments with varying fall velocity of graupel show that for a given microphysics scheme, uncertainties in the parameterization strongly affect the early development of an idealized squall line. In particular, both too fast andtoo slow fall velocities of graupel result in a weaker early development of the squall line, but they lead to different dynamics of hydrometeor population balance. This study also reveals that the impact of the uncertainties in the parameterization of hydrometeor fall velocity on the overall hydrometeor population dynamics varies with different microphysics parameterization schemes, illustrating great uncertainty and complexity in the current cloud microphysics parameterizations used for weather and climate modeling. [ABSTRACT FROM AUTHOR]

Over the past decades, many numerical models have been developed to understand, simulate and predict debris flow processes. Typically, these models simplify the complex interactions between water and solids using a single phase approach and different rheological models to represent flow resistance. Further, different rheological models have different sets of uncertain parameters that need to be specified to simulate debris flow. In this study, we perform a sensitivity analysis for a debris flow numerical model (FLO-2D) to identify the most sensitive parameters for a suite of relevant simulated variables (i.e., run-out distance, maximum flow velocity, minimum flow velocity, deposit depth). We use the Distributed Evaluation of Local Sensitivity Analysis (DELSA) method, which is a hybrid local-global technique. Specifically, we analyze the debris flow event occurred in northern Chile on March 25, 2015. We include two different ravine types: (i) La Mesilla ravine, characterized by a big alluvial fan where considerable sedimentation occurs, and (ii) Acerillas ravine, characterized by a marked narrow channel with almost none alluvial fan, where sediments are mainly transported to the river. We apply the DELSA method for the above ravines, considering eight FLO-2D parameters used to estimate the friction factor. We also examine the influence of topography and grid cell size on parameter sensitivities. Our results show that volumetric concentration and beta2 - a parameter related to yield stress - are the most sensitive parameters, regardless of the target variable. Additionally, different parameter sensitivities are obtained for each debris flow variable (i.e., flow velocity, flow height, deposited area, run-out, etc.). [ABSTRACT FROM AUTHOR]

Recent advances in understanding the scalar transfer across the wind-driven air-water interface, including both experimental observations and numerical simulations, reveal that the transport processes are dominated by the along-wind circulatory motions within the aqueous boundary layer. Such circulatory motions are attributed to coherent elongated eddies arising within the turbulent shear layer and Langmuir cells formed from the interaction between wave drift and shear layer. These streamwise vortices manifest themselves by inducing distinct elongated streaks on the water surface. The population density of these streaks, which can be quantified by the distribution of transverse spacing between streaks, thus characterizes the rate of interfacial scalar transfer. The prevalent notion of transverse spacings between streaks on non-breaking wind-driven wavy surfaces is that, similar to the streaks within a wall boundary layer, the statistics of non-dimensional streak spacing are essentially invariant with Reynolds number exhibiting constant mean value and remarkably similar probability distributions conforming to lognormal behavior. In this study, such statistics are reappraised by analyzing infrared images of non-breaking wind waves at various wind speeds. The experiments were conducted in the wind-wave facility Aeolotron at the University of Heidelberg. Thermal footprints induced by gravity-capillary waves and Langmuir cells are first extracted from the infrared images, and the streaky signatures solely attributed to elongated coherent vortices of the turbulent shear layer are therefore derived. Image segmentation technique is applied to identify the elongated streaks. The streak transverse spacings are then measured, and their ensemble statistics are calculated. The results reveal that the probability distributions of streak spacing all exhibit lognormal probability distribution for various non-breaking wind-wave conditions. The mean streak spacing decreases as the wind friction velocity increases. The non-dimensional mean streak spacing in viscous length scale, however, increases with the wind friction velocity; this contradicts to the previous conclusions that non-dimensional spacings remain to be approximately constant. The oscillatory motions of surface waves on the turbulent shear layer might be the cause of such a variation.This work was supported by the Taiwan Ministry of Science and Technology (MOST 107-2611-M-002 -014 -MY3). [ABSTRACT FROM AUTHOR]

Active source acquisition with cable-free systems ('nodes') implies recording of continuous data over the entire acquisition period (e.g. days to months). Due to the lack of well-defined seismic sources, data outside the shot windows are usually not considered for processing and interpretation, despite the potential useful information contained in the continuous data. Ambient seismic noise interferometry is a suitable method to extract complementary subsurface information from other sources of abundant environmental seismic energy such as road traffic. We present a case study from the ore quarry 'Erzberg' located in central Austria. Seismic investigation of this area aims at characterizing the site response to blasting and subsequently, to optimize the mining process. Furthermore, the subsurface distribution of potential new ore veins is of interest. In November 2016, 125 3C – stations where deployed for three weeks to record both production blasts and specifically designed seismic shots. The acquisition area is 2.5 km by 2.0 km wide and covers both the active mine and its surroundings. The active source data have been processed towards a 3D P-wave velocity model with average velocities ranging from ca. 4 km/s to 5 km/s.Beamforming analysis of the continuous passive data indicate a dominant noise source outside and towards the east of the deployment area. Coherent signals are found in the frequency band 1 Hz to 6 Hz, which is in agreement with the assumption of traffic noise originating from a nearby state road. Ambient noise interferometry is performed by converting each of the recording stations into a virtual source. The resulting virtual source gathers show clear Rayleigh and Love waves on the vertical and transverse components. The moveout of the arrivals indicate apparent surface wave velocities between 1.7 km/s and 1.9 km/s, which would suggest P/S wave velocity ratios in the range of 2 – 2.5. The inversion of surface wave dispersion for a 3D shear-wave velocity model will allow to extract localized P/S ratios and as such contribute to the seismic site characterization. We conclude that active source data acquisition with nodes offers complementary information at negligible additional costs. Traffic noise from a few weeks or even days is sufficient to generate shear wave velocity models, which can be combined with results from active source processing and in turn benefit the interpretation. [ABSTRACT FROM AUTHOR]

Geophysical gravity-driven flows, like avalanches, pyroclastic flows and debris flows, involve the rapid motion of granular mixtures. The full description of the rheological stratification in dry granular flows still represents an open problem. Experimental investigations at the laboratory scale are an essential tool that can provide precious informations about their dynamics. In this work, we present an experimental campaign devoted to the measurement of the velocity and the volume fraction of dry granular chute flows over a loose bed. Optical non-invasive techniques were employed. The employed granular medium consists of acetal-polymeric beads (mean diameter d of 3.3mm) and an internal angle of friction of 27°. All the experiments were carried out in a 2m-long Plexiglas flume with a 8cm-wide rectangular cross section. The upper part of the channel was used as a reservoir where the granular material was loaded and let flow down through an adjustable gate. A small weir was placed at the end of the channel in order to allow the formation of a lower wedge of granular material, corresponding to the erodible bed. Several mass flow rates were investigated by imposing different gate openings.Two high-speed cameras were employed. One camera was placed aside the channel to obtain sidewall velocity and volume fraction measurements while the other camera was located above the free surface. The open-source particle image velocimetry (PIV) code PIVlab [Thielicke and Stamhuis, J. Open Res. Softw., 2014] was employed for estimating the flow velocities. The stochastic optical method (SOM), recently proposed by [Sarno et al., Granul. Matter, 2016], was used to get reliable estimations of the near-wall volume fraction profiles.All the free surface velocity profiles exhibit an approximately parabolic shape, due to the sidewall friction, with a maximum at the cross-section midpoint and a minimum at the sidewalls.All the sidewall profiles can be divided into three zones. In the lower zone, the volume fraction reaches high approximately constant values, close to the loose packing volume fraction (≈0.6), whereas the flow velocities are small and exhibit an exponential tail. Friction among the grains is the main momentum exchange mechanism in this layer. In the central zone, volume fraction still shows high constant values and a linear trend of the velocity is observed. The upper zone, beneath the free surface, was found to be of the same thickness (≈2d) in all the experiments. Herein, the velocity profile show a convex (∂zz(ux)<0) shape and the volume fraction rapidly decreases indicating a more collisional behavior. A velocity threshold was used to identify the interface between the faster flowing layer and the slower one (creep flow) in all the experiments. Interestingly, by aligning the velocity profiles at this meaningful interface, we observed that they collapse onto a unique master curve, with the only exception of the upper collisional layer. It suggests that the flow dynamics is governed by the lower basal boundary condition. [ABSTRACT FROM AUTHOR]

Recent laboratory experiments and the new "patched charge model" have greatly advanced our understanding of dust charging, and subsequent mobilization and transport on the surfaces of airless planetary bodies. Initial launch conditions of lofted dust particles are critical to understand their electrostatic dynamics in various near-surface plasma environments. Here we report results of a series of laboratory experiments about the charge, size, velocity, and rate of lofted dust particles. All lofted dust particles are charged negatively, even under UV radiation, due to the microcavity charging effect described in the patched charge model. The charge is several orders of magnitude larger than values predicted from previous charge models. In addition to single-sized particles, large aggregates are also lofted with the size up to 140 microns in diameter. Preliminary experiments show that the launch velocity is on the order of 1 m/s for particles tens of microns, and smaller particles are lofted with higher velocities. Due to large variations in cohesive force, the launch velocity has a wide distribution. Recent experiments show that dust lofting is a time-dependent process, which begins fast and slows down as time progresses. The transient lofting rate can be as high as several particles per square cm per second, fast enough to supply the lunar horizon glow. These results will advance future studies to explain the existing and future observations on airless bodies that relate to electrostatic dust transport. [ABSTRACT FROM AUTHOR]

We present tomographic results of the crust and the upper mantle beneath Ireland and Britain. A large number of broad-band measurements of surface-wave phase velocities have been accurately collected to produce a state-of-the-art 3D seismic-velocity structure. We applied different surface-wave analysis methods with complementary frequency bands thus sensitive to different depth: cross-correlation of teleseismic surface waves, and waveform inversion. The use of automated techniques led to an unprecedented coverage, making it possible to improve the resolution of the crust and lithosphere of Ireland and its surroundings, compared to previous models. These latest results would contribute to enhance our understanding of the structure and the evolution of the lithosphere beneath the area. [ABSTRACT FROM AUTHOR]

On September 28, 2018, a magnitude Mw 7.5 earthquake occurred in the neck of Sulawesi's Minahasa peninsula. The combined effects of the earthquake and tsunami caused catastrophic damage and more than 2000 deaths. An international tsunami survey team (ITST) was deployed 3 weeks after the event to document flow depths, runup heights, inundation distances, sediment deposition, damage patterns at various scales, performance of the man-made infrastructure and impact on the natural environment. The 23 to 29 October ITST covered a 100 km stretch of coastline circling the entire Palu Bay and adjacent coastlines along the Makassar Strait. A 200 km long reconnaissance flight with an Indonesian Army Mil Mi-17 helicopter provided oblique aerial photography of impacted sites. The collected field survey data includes 130 tsunami runup and flow depth measurements. The tsunami impact peaked inside Palu Bay with flow depths above ground reaching 6 m and maximum runup heights exceeding 10 m. Inundation and tsunami damage was mostly limited to within 0.5 km of the shoreline except along rivers. A rapid decrease of tsunami heights was observed towards the bay entrance and outside of the Palu Bay along the Makassar Strait coastlines. Two tsunami eyewitness video recording locations inside Palu Bay were surveyed for subsequent video image calibration, tsunami hydrograph and flow velocity analysis. We deployed a Leica BLK360 scanner from the NHERI RAPID facility. We acquired precise topographic data using terrestrial laser scanning (TLS) at selected video sites with multiple scans acquired from different instrument positions. These ground-based LiDAR measurements produce 3-dimensional "point cloud" datasets. Digital photography from 3 scanner-mounted cameras yields full dome panoramic images overlaid on highly accurate point clouds. The main coastal road in Palu was overwashed with flow velocities of more than 7 m/s. Field observations, drone videos, helicopter and satellite imagery are presented. Eyewitnesses interviewed based on established protocols indicate rapid tsunami arrivals within a few minutes of the earthquake. We educated residents about tsunami hazards as community-based education and awareness programs are essential to save lives in locales at risk from locally generated tsunamis. [ABSTRACT FROM AUTHOR]

Like all NASA missions, InSight's data will be archived at the Planetary Data System (PDS), a long-term digital data archive. This includes data from SEIS, the first seismometer deployed on the Martian ground (40 years after the Viking deck-mounted instruments), as well as those of the Auxiliary Payload Sensors Suite (APSS). For SEIS, the distributed data are those of the very broad-band (VBB), short-period (SP) sensors, SEIS electronics, leveling system, and selected lander telemetry channels.SEIS and APSS data are received from the spacecraft in raw telemetry packets and converted to both SEED format files and ASCII tables (GeoCSV) for analysis and archiving. APSS data in SEED format will permit straightforward data comparison. Both data sets will then be delivered to the Mars SEIS Data Service (MSDS) at IPGP Data Center. IPGP maintains the SEIS data portal, which will become open-access a week prior to the first public data distribution. MSDS will also deliver SEIS data to PDS for archiving and to IRIS as a second data portal. IRIS, an InSight educational partner, has the goal of engaging students with seismic data from Mars. The IRIS Data Management Center and MSDS will make data from the seismometer available to students, the international seismological community, and the public. Data for schools will be distributed via several international "seismo@school" projects.The initial release of raw data archive products to the PDS, covering the period from landing to the start of the science monitoring phase, will occur within 3 months of the start of the science monitoring phase (anticipated April 2019), with calibrated products and SPICE kernels following a month later. After these initial releases, the calibrated and SPICE data will be released by the PDS every 3 months, beginning in July 2019. Public release of "uncertified" seismic velocity data via IRIS will start about 7 months after the start of the science monitoring phase and will be made every 4 weeks. [ABSTRACT FROM AUTHOR]

The specific controls modulating recent glacier changes in the Central Himalayas are still relatively poorly understood. This hinders our ability to predict future glacier changes in this region, which is vital for water resource management. In this study, we mapped changes in area, surface elevation and surface flow velocity of 162 glaciers in the Annapurna Conservation Area in Nepal since 2000 using satellite imagery. We examined the influence of glacier surface gradients, minimum and maximum elevations, hypsometry, disposition to be avalanche-fed and supraglacial debris on recent glacier changes. We found that total glacier area decreased by 8.5 % (n = 162) between 2000 and 2014/15, and mean surface elevation change was -0.33 m a-1 and mean glacier mass balance was -0.28 m w.e. a-1 between 2000 and 2013/16 (n = 72). Ice surface velocities decreased on seven glacier tongues between 2002 and 2016. We found orographically-driven south-to-north positive trends in glacier mass balance. However, within these trends, glacier changes were heterogeneous between glaciers and between sub-regions. In the Damodar Himal in the north of the Annapurna region, glaciers that had lower maximum elevations, bottom-heavy hypsometries and were more avalanche-prone, tended to lose the most mass. However, these trends were not clear in glaciers in Central Annapurna. This is attributed to differences in the glacier characteristics between the two sub-regions. This study presents new glacier change data in the previously little-studied Annapurna region and sheds light on the influence of different glacier-specific controls on individual glacier behaviour. [ABSTRACT FROM AUTHOR]

Jakarta exhibits among the fastest subsidence rates on Earth with up to 20 cm/year. It thus exposes over 30 million inhabitants to dramatic flooding due to the rising of ocean levels. Jakarta is also a relatively thick sedimentary basin that is known to amplify ground motions and will likely be prone to intense liquefaction during the next strong earthquake. We use a temporary deployment of broadband seismic stations between 2013 and 2014 to explore the temporal evolution of seismic velocity and seismic attenuation. We use both inter-station and single-station correlation functions in all components of the correlation tensor to map the changes at various spatial scales. We also explore the stability of our results with various methodologies to measure changes in seismic velocities (e.g., moving window cross spectrum, stretching, dynamic time warping, and wavelet cross-spectrum). These changes in velocity and attenuation yield changes in future ground motions, which we quantify using ground motion prediction equation and pseudo-analytical wave modeling. Finally, we correlate our results with remote sensing observation of land subsidence. [ABSTRACT FROM AUTHOR]

Understanding ocean features and their variability at different spatial and temporal scales by integrating multi-platform observation system is still one of the major scientific challenges. The LOng-term Glider Missions for Environmental Characterization 2017 (LOGMEC17) is a multi-platform, multi-scale, multi-disciplinary combined acoustical and oceanographic campaign, aimed at studying the variability and predictability of Ligurian Sea characteristics at different scales. LOGMEC17 took place in autumn 2017 and involved research vessels but also gliders, moorings, towed vehicles, satellites and HF coastal radar providing a variety of ocean measurements.The two deep gliders have been programmed to follow the repeat cycle satellite tracks of Jason-3 and Sentinel-3, collecting about 50 days of data up to a depth of 1000m. The comparison between glider-derived Dynamic Height and altimeter Absolute Dynamic Topography was carried out using the co-located and near-contemporaneous remote and in-situ measurements. Furthermore combined analysis of remote sensing observations and glider data was useful to trace the path and variability of the most relevant water masses in the Ligurian Sea.The ocean current time-series obtained by the upward-looking ADCPs mounted to the two moorings deployed in the Eastern part of the Ligurian Sea show periodic tilted stripes. The spectral analysis highlights a power peak in the near-inertial frequency band slightly higher than the theoretic inertial frequency f (blue shift). The velocity shear clearly identifies an upward phase velocity, implying downward energy propagation. In order to further investigate the NIWs characteristics, the rotary auto spectra of the currents observed at the two moorings was carried out. Results indicate that at the near-coastal mooring (43.87°N 9.83 °E, water depth 100m), the strongest power in the near-inertial band was found between 45 and 65m depth, while at the open-sea mooring (43.86°N 9.21 °E, water depth 250m) results indicate a more vertically uniform power spectra with a strong signal identified between 70 and 120 m depth. [ABSTRACT FROM AUTHOR]

Our current understanding of Earth's interior is derived almost entirely from seismology. However, observations of seismic velocity alone are insufficient to distinguish between various rock types and mineral assemblages that may exist in the lower continental crust. Seismic studies have served us well in understanding the mantle and the core, but our knowledge of the continental crust is far less comprehensive. Unlike the mantle, the crust is both compositionally and structurally complex, and conclusive seismic interpretation can be challenging. Seismic anisotropy is the directional dependence of seismic velocity and, if characterized accurately, provides the potential to interpret subsurface deformation conditions and to differentiate between rock types and mineral assemblages. As rocks are deformed at lower crustal conditions, their constituent minerals respond by aligning in crystallographic preferred orientations (CPO). A rock's elastic properties can be derived from the combinations of the single-crystal elastic tensors for each mineral grain in their constituent orientations. Textures with a strong CPO result in seismic anisotropy. Formulating an accurate interpretation of seismic signals associated with anisotropy requires a simplified assumption of symmetry of the bulk elastic tensors; most commonly, transverse isotropy is assumed. However, the true elastic symmetry of most crustal rocks is far more complicated, and relatively few have been characterized. The effects of inaccurate assumptions of transverse isotropy on seismic inversions have not been evaluated thoroughly and, without a clear understanding of these effects, our use of seismic observations to interpret lower crustal composition and structure is limited. The objective of this work is to further evaluate the factors influencing the magnitude and symmetry of seismic anisotropy in the lower crust, specifically rocks from the Pelham gneiss dome in north-central Massachusetts, so that we may more accurately model seismic signals with respect to specific rock compositions and structures. We have collected a suite of 77 oriented samples covering the five common rock types in Pelham dome: felsic gneiss, felsic schist, mafic gneiss, mafic schist, and quartzite. We use electron backscatter diffraction (EBSD) to measure mineral CPO, and then calculate the aggregate elastic tensors. We will use symmetry decomposition to evaluate the commonly made symmetry assumptions for Pelham dome rocks. EBSD data from approximately half of our total sample suite will be presented and discussed. Our goal is to improve the ability to use seismically determined elastic tensors to infer rock type, mineralogy, and deformation processes, while adding to the database of elastic tensors for lower crustal rocks. [ABSTRACT FROM AUTHOR]

The structure of gravity currents has been extensively studied using both and laboratory and numerical methods. Much of the previous work has focused on lock-exchange type flows that typically result in an exaggerated current head and a distorted turbulence distribution. The work presented herein investigates steady state flows, primarily looking at the structure of the body of the flow. Within most natural flows the body of the flow forms the majority of the current. Similarly, the flow is typically assumed to be two-dimensional within experimental and numerical studies. This study aims to quantify the three-dimensional turbulent structure of steady state gravity currents.A combination of three-dimensional direct numerical simulation (DNS), planar particle imaging velocity (PIV) and tomographic (volumetric) PIV has been used to investigate the body of pseudo-steady gravity currents, and more particularly the impact of Reynolds and Schmidt numbers on the formation of coherent turbulent structures. These structures are of interest due to their ability to control the distribution of mass, momentum and temperature, as well as their potential impact on erosion and deposition in particle laden flows. PIV was used to investigate a range of Reynolds numbers by considering various slopes with a constant influx, as well as a constant slope with varying influx. DNS, carried out using the spectral element code Nek5000, was used to investigate a range of Schmidt numbers, as well as a potentially wider range of Reynolds numbers than experimentally achievable, with a constant influx and varying slope. Multiple vortex identification techniques were utilised to identify the number and size of structures within the flow. This study describes the three-dimensional turbulent structure of the body of pseudo-steady gravity current flow for the first time. Both the laboratory and numerical data reveal the complex three-dimensional flow present within gravity currents from a simple ducted domain. The results show that cross-stream and vertical flow velocities within these currents are of very similar magnitude. Turbulence structure is dictated by both the Reynolds and Schmidt number. The impact of these structures on the dynamics was then established: it was found that increasing the Reynolds number results in a greater number of smaller vortices, while increasing Schmidt number suppresses the formation of structures and reduces the thickness of the mixed layer. [ABSTRACT FROM AUTHOR]

The velocity distribution inside the deep Earth can be illuminated using a wide range of seismological techniques. This has revealed a number of surprising structures, such as the Large Low Shear wave Velocity Provinces (LLSVPs), that have been linked to fundamental behaviour of Earth's large scale convection. Since these structures should possess anomalous density, they are expected to be represented in Earth's long wavelength gravity field.However, it is unclear how to determine the density anomaly associated with deep mantle structures from seismology. Commonly it is assumed that velocity and density are correlated, due to their common dependence on temperature. However, in the deep mantle, the scaling of velocity to density is highly uncertain, due to incomplete knowledge of mineralogy and rock properties at high pressures. In addition, compositional variations become more important in the deep Earth, because thermal expansivity is reduced at high pressure. If velocity anomalies are caused by compositional variations, there might be no or even a negative correlation of density and velocity. These theoretical problems are further compounded by methodological differences between different seismological methods, which lead to disagreements in terms of velocity anomaly magnitude and spatial structure.As an alternative to converting velocity to density, we propose to use the recently developed idea of votemaps. Votemaps codense information from several seismic models, by counting at each position how many of the seismic models show a significant velocity anomaly (relative to the velocity scale of each model). In this way, probable locations of anomalous features are defined. We use a linear inversion to determine the density of each feature, by fitting the measured gravity field. Since it is unclear how much deep Earth signals are hidden by shallow density anomalies in the lithosphere, we will use both the isostatic gravity anomaly and a gravity anomaly determined by stripping the gravity effect of the seismological model Crust1.0. [ABSTRACT FROM AUTHOR]

We present the results of a new global Bayesian tomographic inversionfor a radial anisotropic shear wave velocity model of the Earth. Thedevelopment of radial anisotropic shear wave models are useful forunderstanding mantle dynamics. Our model improves on existing work byproviding robust estimates of uncertainties.A key aspect of this new model is the careful selection of surfacewave observations produced by earthquakes from the Harvard CMTcatalog. We automatically process a large set of seismic signalsrecorded for these events by simultaneously inverting Love andRayleigh waveforms up to the fifth overtone. After initial processing,only events where high quality Love and Rayleigh surface waves areobserved are retained for the tomographic inversion. This careful dataselection ensures that inference of radial anisotropy is not biaseddue to variations in spatial coverage of Love and Rayleigh observations.Our tomographic inversion uses a novel Bayesian Trans-dimensional Treeapproach that dynamically adapts the complexity of the solution toincrease spatial resolution where observations provide additionalconstraint. This leads to a robust estimation of both the shear wavemodel and its uncertainties. Furthermore, we demonstrate how ourapproach can be extended to a joint inversion to include body shearwaves to further constrain radial anisotropy of the Earths mantle. [ABSTRACT FROM AUTHOR]

Low-lying communities protected by dykes are at increasing risk to climate change impacts. A strategy that is increasingly recognized as a viable option for flood protection and mitigation of these communities is managed realignment of dyke infrastructure. In hypertidal, developed estuaries such as the Salmon River Estuary in the Upper Bay of Fundy, the town of Truro, Nova Scotia, is one such community that may benefit from managed realignment to expand the floodplain. Before managed realignment is implemented, hydrodynamic modelling must be done to determine the best location for new dykes further inland and breaches in the existing dyke infrastructure. This task presents challenges, however, as the bathymetry of the Salmon River is highly variable due to its hypertidal environment with high suspended sediment concentrations and frequent high river discharge events. To address this challenge, Delft3D was used to model the hydrodynamics within a portion of the Salmon River south of the Onslow North River Marsh Body and identify the sensitivities presented in model outputs as a result of changing the bathymetry. Model outputs using bathymetry from the spring of 2014 are compared to model outputs using newer bathymetry that was collected in August 2018 using a SonTek M9 HydroSurveyor at high tide times and an unmanned aerial system (UAS) survey of the edges of the Salmon River at low tide times. The hydrodynamic model was initialized and calibrated using WebTide, a tidal prediction model, and four water level recorders. To validate the model results, field data were collected at the same time the new bathymetry was collected and during the same time period the model was run for in August 2018. This includes the deployment of two Acoustic Doppler Velocimeters (ADVs), two Acoustic Doppler Current Profilers (ADCPs), two Optical Backscattering (OBS) sensors, and two water samplers (ISCOs) over four tidal cycles in August 2018 to collect information on flow velocity, water depth, and suspended sediment concentration. Preliminary results of field data collection show flow velocities ranging from approximately 0.06 m/s to 0.77 m/s over a tidal cycle, water depths upwards of 2.71 m above mudflats that are dry at low tide, and suspended sediment concentrations upwards of 70 g/L. Validating model results with these results will help determine the ability of Delft3D to simulate real hydrodynamic conditions in the Salmon River and whether hydrodynamic models are necessary for planning and implementing managed realignment projects in low-lying coastal communities. [ABSTRACT FROM AUTHOR]

The viscoelastic Earth structure beneath the Antarctic ice sheet is an important control on future ice sheet dynamics and a key factor in ice and sea-level reconstructions. However, constraining viscoelastic structure in the mantle beneath the Antarctic is challenging. Relative to other formerly or currently glaciated areas, Antarctica has a paucity of records that constrain local viscosity. Moreover, while seismic studies indicate that three-dimensional mantle structure beneath Antarctica is complex, and includes a low viscosity upper mantle in the West, the conversion from seismic wave speed to viscosity is subject to considerable uncertainty. These challenges have motivated the recent application of Global Position System (GPS) data, in tandem with forward models of crustal deformation due to glacial isostatic adjustment (GIA), to infer 1-D viscoelastic structure beneath various parts of the West Antarctic (Nield et al., 2014; Zhao et al., 2017; Barletta et al., 2018).However, important questions regarding these GPS-based modeling techniques remain unanswered. What specifically do these 1-D viscosity models represent in an area with complex 3-D mantle structure, and over what geographic length-scale are they applicable (on the scale of a single glacier catchment, the entire West Antarctic, or somewhere in-between)? To investigate these questions, we generate synthetic "observations" of present-day crustal deformation rates using 3-D viscoelastic Earth structure inferred from seismic tomography and a finite volume treatment of GIA (Latychev et al., 2005), and compare these rates with a suite of 1-D forward Earth model predictions. Furthermore, given that horizontal deformation rates are highly sensitive to 3-D Earth structure in this region (Powell et al., 2018), we also test whether and how much their inclusion will improve any inference of 1-D Earth structure. The results have significant implications for analyses of Earth structure in the region and for projections of Antarctic Ice Sheet stability in a progressively warming world. [ABSTRACT FROM AUTHOR]

Aquifers beneath big cities are considered a very important resource from an energetic and water supply point of view. Unfortunately, the amount of disposable water and its energetic potential are limited over a long term perspective. In this context, the monitoring of physical-chemical parameters and the assessment of water and energy balances at the city scale is crucial for the evaluation and the preservation of the resources. In order to assess and to optimize the exploitation of the subsurface low-enthalpy geothermal potential of aquifer systems and to predict the evolution of the thermal regime, heat transport processes, both advective and conductive, must be considered. This requires the hydraulic head and the fluid flow velocity field to the be accurately characterized. Numerical modeling has been commonly adopted to estimate homogeneous equivalent hydraulic properties and, trying to calibrate them, to reproduce hydraulic head fluctuations. Nevertheless, if the homogeneous equivalent models can reproduce very well the hydraulic head variations, the fluid flow velocity field is almost always incorrect, and this can generate problems in the heat advection assessment. This is often due to local heterogeneities that are usually not represented but that are crucial for transport simulations. This work aims to describe the spatial variability of the hydraulic and thermal properties of an aquifer starting from borehole log descriptions and grain size distribution analysis and trying to integrate them in a coupled fluid-flow and heat-transfer 3D finite element model. This objective is achieved by converting qualitative borehole log stratigraphic information into hydrogeological and thermal parameters (e.g., hydraulic conductivity, storativity, thermal conductivity) and by interpolating these parameters over the mesh nodes through 3D kriging techniques. This approach is applied to a case study in a decommissioned large industrial district located in Milan (Northern Italy). The local stratigraphic sequence consists of fluvioglacial deposits separated vertically by low permeability layers, resulting in 3 main aquifers showing significant lateral and vertical heterogeneities within the study area. This study shows how the redevelopment of former industrial areas in highly urbanized contexts must be planned carefully to take advantage of the natural resources (i.e., water and energy) and to minimize the impacts of new buildings on the subsurface environment. [ABSTRACT FROM AUTHOR]

Santorini is the most active arc volcano of the Hellenic subduction zone and has a history ofalternating effusive, shield-forming eruptions and explosive caldera collapse. The most recentcaldera-forming event is the well-studied 3.6 kyr Late Bronze Age (LBA/Minoan) eruption.In 2011-2012, the volcano experienced inflation and seismicity attributed to magmaintrusion between 3.3 and 5.9 km depth. To investigate processes that control calderaformation and the accumulation of magma at arc volcanoes, we use a high-resolution,P-wave, seismic velocity model together with existing geological and geochemicalconstrains. The PROTEUS experiment collected dense, 3D, active-source marine-landseismic data using 90 ocean bottom seismometers, 65 seismic land stations, and∼14,300 controlled-sound marine sources from the U.S. R/V Marcus Langseth.We use seismic tomography to invert &#x003E;220,000 Pg travel times to image of theupper crustal structure to 7 km depth. Regional geology and tectonic features arereflected in the near-surface velocity structure. Magmatism has localized along NE-SWbasin-like structures that connect the Christiana, Santorini, and Kolumbo volcaniccenters, indicating a strong interaction between magmatism and tectonism. In theupper 3 km beneath the north-central caldera, we find a ∼3-km-wide, cylindricallow-velocity anomaly (-2 km/s) that lies directly above the pressure source of 2011-2012inflation and between two NE-SW-striking tectonic lineaments. Vents that formedduring the first three phases of the LBA eruption locate near the edges of the imagedstructure. We infer that collapse of a limited area of the caldera floor resulted ina high-porosity, low-density cylindrical volume, which formed by either chaoticcollapse along reverse faults, wholesale subsidence and infilling with tuffs andignimbrites, phreatomagmatic fracturing, or a combination of these processes. LBAphase 4 eruptive vents are located along the margins of the topographic calderaand the velocity structure indicates that the wider topographic caldera formed bycoherent down-drop following the more limited collapse in the northern caldera. Thisprogressive collapse sequence is consistent with models for multi-stage formationof nested calderas along conjugate reverse and normal faults. The upper-crustaldensity differences inferred from the seismic velocity model predict differences insubsurface gravitational loading that correlate with 2011-2012 edifice inflationindicating that sub-surface density anomalies may influence present-day magmaaccumulation. Directly beneath this structure, we image a second low-velocityanomaly that is 3-6 km below the northern caldera basin, 3-5 km wide, and elongated∼15 km NE-SW, parallel to tectonic structures. The largest-amplitude recoveredvelocity anomaly (-1 km/s) is consistent with 4-10% melt and coincides with the2011-2012 Mogi pressure source. Significant ray bending indicates that the recoveredsize and amplitude of the low velocity volume are minimum bounds. We infer anupper-crustal intrusion rate (∼2.6 km3/ky) consistent with the inferred long-termgrowth of the shallow magma system at Santorini. Future analysis of waveforms,reflectors, and shear waves, and full waveform inversion, will better constrain themelt content and distribution of crustal magma accumulation beneath Santorini. [ABSTRACT FROM AUTHOR]

Rock avalanches are large volume (&#x003E; 106 m3), extremely rapid, and highly mobile landslidesthat on entering fjords, lakes and the ocean, can trigger tsunamis. The tsunamis can havefar-reaching impacts beyond the extent of the initiating rock avalanche, posing a risk tocoastal communities. Modelling the runout of terrestrial rock avalanches into the water canimprove the understanding of emplacement processes, particularly over changes in medium(from air to water). It can also provide input parameters, including impact velocity, slidethickness distribution, slide mass, and runout distance, for numerical tsunami modelling.Where there are groups of closely spaced rock avalanches, these provide a rheologicalenvelope for key model parameters that can aid in scenario planning for futureevents. Here we present the modelling results of a group of post-glacial rock avalanche depositsin Milford Sound/Piopiotahi. Using the single-phase, depth-averaged numericalmodel DAN3D, we simulate a representative subset of rock avalanches identifiedby multibeam echosounder (MBES) on the fjord bottom. Initial results suggestthat modelling the change from air to water is effectively achieved by assuming adifference in the basal rheological parameters along the flow path at the water level.The results of the numerical modelling provide information on the rock avalanchedynamics including flow velocity, thickness distribution, and frontal geometry as theavalanche enters the water. These results can form the basis for tsunami modelling. [ABSTRACT FROM AUTHOR]

The presence of the broadband electrostatic emissions, which are routinely observed by satellites, can be understood on the basis of the existing theories of electrostatic wave generation in inhomogeneous equilibrium configurations. Satellite observations show that the electrostatic instability, which is expected to occur in most cases due to an inhomogeneous energy density caused by a strongly inhomogeneous transverse electric field, sometimes does not develop inside nonlinear plasma structures in the high-latitude region, even though the velocity shear is sufficient for its excitation. In this study, it is shown that the instability damping can be caused by out-of-phase variations of electric field and field-aligned current inside these structures. The sources of free energy required for the wave generation do not generally act in unison so that their combined effect turns out to be close to zero.The work was partly supported by Russian Science Foundation №17-77-20009. [ABSTRACT FROM AUTHOR]

The South China Sea lies at a key junction between major plates (i.e. Pacific, Eurasian and Indo-Australian) within one of the most tectonically complex regions in the world. A great diversity of plate reconstructions has been proposed for the South China Sea area since the Cenozoic. One class of 'conventional' proto-South China Sea plate models suggests that South China Sea opening was accommodated by one-sided, southward Proto-South China Sea subduction beneath Borneo during the Eocene and Early Miocene (e.g. Hall and Breitfield, 2017; Holloway, 1982; Taylor and Hayes, 1983). In contrast, an 'alternative' model proposed double-sided Proto South China Sea subduction within the same time period (Wu and Suppe, 2017). The alternative model was proposed to explain the origin of a slab-like, sub-horizontal fast tomographic anomaly below the present South China Sea at 500 to 700 km depths that exceed 1000 km in N-S and E-W extent (Wu and Suppe, 2017). A recent mantle flow model assimilated the conventional-style plate model (Zahirovic et al.,2016) and, despite many valuable insights, did not clearly reproduce a sub-horizontal slab below the present South China Sea.This study assimilates these two end-member plate models into the numerical model TERRA (Bunge et al., 1998). The computational domain is discretized on a regular grid based on the icosahedron, for a total of ~80 million grid points and a resolution of ~25 km, allowing us to simulate convection in the same regime as the real Earth. We implemented the plate models as a set of continuously closing plates in order to generate a global self-consistent velocity field to be assimilated into the convection models. We explicitly tested the viability of the two plate models against tomography following Schuberth et al. (2009) by converting the resulting temperature field to seismic velocities and applying a resolution filter from S40RTS (Ritsema et al., 2011). Our results show that the two plate models produce fast anomalies under the present-day South China Sea that are distinguishable, even within the coarser-scale S40RTS resolution filter. The alternative model produces more slab-related cold anomalies under present-day South China Sea. We will discuss a next set ofthermochemical model results that were designed to increase realism by incorporating possible oceanic and continental compositional differences. [ABSTRACT FROM AUTHOR]

Debris flows can be defined as very rapid to extremely rapid surging flows of saturated debris in a steep channel. Debris flows pose a significant hazard to infrastructure and the loss of life due to the combination of high flow velocities, large impact forces, long runout distances and poor temporal predictability. Entrainment of channel-bed material along the flow path can be an active process in debris flows, which can affect the volume and flow dynamics. The grain size and degree of saturation of the debris has also been noted to affect flow dynamics and runout distance. However, the composition of debris flows is often overlooked because it is difficult to constrain material properties from debris flow deposits in the field, even though the composition of a debris flow strongly affects the deposit geometry, such as the height and width of levees and lobes. Therefore, there is a current need to be able to systematically incorporate the processes and time-frame that recharge debris to the channel and their respective grain sizes into monitoring and characterization of debris flow hazards. The successful incorporation of these parameters will help refine hazard analyses and mitigate future losses. Terrestrial laser scanning (TLS) has been conducted in the White Canyon in Interior British Columbia (BC), Canada since early 2012 as part of the Canadian Railway Ground Hazard Research Program. The White Canyon located just outside the community of Lytton, BC, has been a central focus of this research effort. Over the 5+ years of TLS monitoring at the White Canyon, several debris flows have occurred on this active slope. In a few cases, these events have overwhelmed mitigation and have directly impacted the track. These events disrupt the safe operation of rail traffic through this major transportation corridor. In this work, we use the high-resolution TLS datasets to derive the volume of in-channel stored sediment and the grain size of the stored debris in select channels of the White Canyon. Machine learning algorithms are applied to characterize the grain size in the debris accumulations in the channels. We additionally link rockfall activity to in-channel stored sediment to characterize the channel recharge processes on this active slope. Developing a better understanding of debris channel recharge processes will continue to advance the practices of natural slope mitigation planning and ongoing control as they pertain to ensuring the safety of the workers and integrity of infrastructure. [ABSTRACT FROM AUTHOR]

Regions of low seismic velocity below mid-ocean ridges, volcanic islands, and active riftzones are routinely interpreted to be due to the presence of some quantity of partial melt. Thisis somewhat logical, given the evidence of magmatism at the surface. However, the exactquantity of melt, or the porosity, within the upper mantle remains elusive. Regions of lowseismic velocity below, for example Iceland, Afar, and La Réunion have historically beeninterpreted to be due to a porosity of up to 0.05. Such high retention of melt would requireslow rates of melt transport, on the order of cm yr−1. Yet U-series isotope studiesand the apparent climatic sensitivity of volcanism at both Iceland and mid-oceanridges would suggest that melt rises rapidly, at rates of 10 m yr−1 or more. Wecannot have both situations. To try and unravel this dichotomy we aim to predict theseismic observations by using a geodynamic model to calculate porosity, and theseismic structure for various physically reasonable scenarios of partial melting.The key uncertainty is permeability, which links melt transport rates to porosity.Focusing on La Réunion, we use the predicted seismic structure for the full waveformpropagation of source earthquakes to make comparisons between synthetic and observedseismic arrivals. Using the SKS arrivals from 21 source events at epicentral distancesof between 60 and 120∘, we find that the travel time delay correlates best withmodels that predict mean porosity of ∼ 0.03, with a low rate of melt transport.However, the waveform misfit for the SKS arrival correlates best with models thatpredict a very low mean porosity of &#x003C; 0.01 and fast transport. Given waveform misfitand isotope studies would both suggest fast transport, perhaps classic travel timetomographic studies have overestimated the retention of melt in the asthenosphere. [ABSTRACT FROM AUTHOR]

Velocity properties of the heterogeneous crust are required for solving a wide range of geophysical problems, including earthquakes hypocenters location and deep structure investigation for delineating geological anomalies of different nature. In this work, we considered an unusual approach of subsurface characterization on the basis of P- and S- waves travel times – so-called "reverse wave" method for areas of dense seismicity. Considered method is based on the principle of wave reversibility with is that the travel time of the seismic wave propagating from the source to the receiver is equal to the travel time of wave propagating from the receiver to the source. This principle allows us to consider quite a bit of travel times of seismic waves running from sufficiently weak local earthquakes to some seismic station as the reversal waves travel times, propagating from this seismic station to the hypocenters of the corresponding earthquakes. Thus, the initial parameters for velocity distribution reconstruction includes coordinates of the earthquake hypocenters and seismic wave travel times corresponding to the particular seismic station. The novel algorithm to find the solution of the inverse problem is developed which incorporates the iteration procedure to improve the reconstruction results and imposes additional smoothness conditions on the reconstructed values. Several numerical experiments based on forward problem solution were performed. Waves travel times in 3D heterogeneous medium have been calculated in the ray approximation. It made it possible to estimate the effect of various parameters including earthquakes density, size and shape of the velocity anomalies on the residual of the reconstructed velocity distribution. Obtained results allow us to choose optimal parameters for calculation of the velocity distribution depending on the set of initial data and make a comparison with tomographic methods.The work was carried out with the financial support of the grant of the President of the Russian Federation to support scientific schools No. SS-5545.2018.5. [ABSTRACT FROM AUTHOR]

Hagen Glacier is a major marine-terminating outlet-glacier that drains 6 % of the Northern part of the Greenland ice sheet. This part of the part of the ice sheet is critically understudied, and here we show that the dynamics of the glaciers in the region can be highly variable, potentially impacting the total mass budget of the whole northern sector. We present 35 years of ice velocity measurements derived from both synthetic aperture radar (Sentinel-1) and optical satellite data (Landsat). In conjunction with satellite observations of glacier area change and surface elevation change, the data document the surge of Hagen Glacier starting in 2002 in high detail, and reveal both prior and subsequent dramatic changes in flow regime and geometry. During the past 35 years, Hagen Glacier has experienced three distinct flow regimes: i) a long period of 'stagnant' flow causing a general thickening, ii) a period of fast flow with speed-up occurring over winter and iii) a deceleration with constant flow velocities during the winter and a marked summer speed-up. We investigate the possible drivers and controls of the observed changes in the context of atmospheric and ocean forcings, and discuss the future of glacier. [ABSTRACT FROM AUTHOR]

We present an analysis of wind regimes across four different sites of varying forest density and height. The threshold between the weak-wind and the strong-wind regime for the entire canopy is derived using the hockey stick-like dependence of the friction velocity on the mean advective wind speed. The height dependence of thresholds within the canopy is inverted compared to the one above grassland sites. We hypothesize that this can be understood by extending the accepted interpretation for weak-wind thresholds from grassland sites to forested sites.Even for large fluctuations above the canopy, the fluctuations of the vertical wind velocity in the subcanopy remain small during weak-wind situations. Correspondingly, in the strong-wind regime, turbulence in the subcanopy remains strong in spite of reduced above-canopy turbulence. This fact suggests that previously used methods for determining the degree of coupling across the canopy layer based upon the ratio of the vertical wind variance between the above-canopy and subcanopy may prove erroneous.The transport of mass and energy between the subcanopy and above-canopy layers is significantly reduced during the weak-wind regime. In particular, the vertical turbulent transport is reduced by more than one order of magnitude. This suggests a decoupling of the subcanopy layer during weak-wind situations and allows for the accumulation of carbon dioxide originating from soil respiration in the subcanopy layer during the weak-wind regime. [ABSTRACT FROM AUTHOR]

The complex nature of the core-mantle boundary (CMB) is well reflected in numerical mantle convection models. Observed thermal and chemical features are cold subducting slabs, hot rising plumes and dense piles. Particularly plumes are of importance as they are responsible for a number of structures. We find plume clusters when smaller plumes merge and line-plumes that leave a more elongated structure at the CMB. Additionally, plumes are known to push dense material up to form the piles which are related to the large low shear velocity provinces (LLSVPs). Typically dense material is inserted to the models by prescribing the thickness and density of an enriched layer at the lower boundary. Here we present another mechanism in which plumes play an essential role in order to form piles but without prescribing a dense layer. In our thermochemical model of mantle convection piles form by convection-assisted diffusion. The chemical transport across the CMB is strongly connected to plumes rising from the CMB. We discuss and compare the results of these self-organised structures to those obtained from our models in which an initial dense CMB layer is prescribed. [ABSTRACT FROM AUTHOR]

The whole North Atlantic region has highly anomalous topography and bathymetry. Observations show evidence for substantial topographic change with rapid onshore uplift close to the Atlantic coast and simultaneous subsidence of basins on the continental shelves, most likely throughout the Mesozoic. We present a review of geophysical data and interpretation of the whole region with emphasis on data relevant for assessing topographic change. We review the available data on topography, bathymetry, density, seismic velocity, and heat flow and present interpretations of the structure and composition of the crust and lithospheric mantle. We find that most of the northern North Atlantic Ocean has anomalously shallow bathymetry although it follows the "normal" square-root-of-age dependence, which however is elevated by up-to 2 km. Nevertheless, the heat flow variation follows the square-root-of-age dependence, although heat flow is anomalously low on the spreading ridges around and on Iceland. In apparent contrast, exceptionally low seismic velocities are observed along the spreading ridges around and below Iceland. Near-zero free-air gravity anomalies indicate that the oceanic areas are mainly in isostatic equilibrium, whereas anomalously low Bouguer anomalies indicate low density in the uppermost mantle. Anomalously thick oceanic crust is observed along the Greenland-Iceland-Faro Ridge and extending into the Davis Strait. We propose that the anomalous bathymetry is caused by compositional variation in the lithosphere, which indicates. that the oceanic lithosphere may include remnants of continental lithosphere.The onshore circum-Atlantic areas show rapid uplift close to the coast with rates up-to 3 cm/yr. This is surprisingly associated with strong positive free-air gravity anomalies which predicts isostatic subsidence. However, negative free-air gravity anomalies in onshore Canada and Bothnian Bay explain recent uplift in the shields as isostatic rebound after glaciation. Archaean lithosphere is everywhere thick in both Greenland and Fennoscandia, Proterozoic areas have thinner lithosphere and Palaeozoic-Mesozoic areas have very thin lithosphere. It is enigmatic that the presumed Archaean-Proterozoic Barents Sea region is submerged and includes deep sedimentary basins. [ABSTRACT FROM AUTHOR]

Turbulent boundary layers of natural atmospheres can be several orders of magnitude thicker than those of wind tunnels. Yet, it is quite common to assume that initiation threshold friction velocities derived from wind tunnel experiments also describe transport initiation in the field because the standard viewpoint is that mainly the mean flow field matters. However, observations seem to challenge this viewpoint. For example, according to wind tunnel measurements, sand transport on Mars should be very rare in the present climate on Mars, but observations suggest widespread and persistent sediment activity [1]. Or, in developing boundary layer wind tunnels, aeolian transport is first initiated at the downwind end of the test section, where friction velocities are smallest and the boundary layer thickest [2]. Here, based on a theoretical analysis and a reanalysis of wind tunnel experiments from the literature, we show that the nondimensionalized threshold friction velocity (Bagnold's threshold parameter) is a function of the particle Reynolds number and the ratio between boundary layer thickness and particle diameter (but not of the density ratio) for cohesionless conditions [3]. One of the most important conclusions is that aeolian transport in the field may be much more readily initiated than in wind tunnels because of a much thicker boundary layer.[1] Sullivan & Kok (2017), https://doi.org/10.1002/2017JE005275[2] Williams et al. (1994), https://doi.org/10.1111/j.1365-3091.1994.tb01408.x[3] Pähtz et al. (2018), https://doi.org/10.3390/geosciences8090314 [ABSTRACT FROM AUTHOR]

We present a comparison of the present-day crust to upper-mantle (400km) structure in the Western Mediterranean along two NW-SE oriented transects in the Alboran and Algerian domains. The Alboran domain transect crosses the Betics, the Alboran Basin, and the northern margin of Africa between the Tell and Rif mountains. The Algerian domain transect crosses Valencia Trough, the Balearic Promontory, the Algerian basin and ends in the Tell-Atlas Mountains in the northern margin of Africa. We model the thermal, compositional, density and seismic velocity structure, also incorporating slabs imaged by seismic tomography using recently updated version of the LitMod2D, an integrated geophysical-petrological modelling tool. LitMod2D combines data from petrology, geochemistry and geophysics in a self-consistent thermodynamic framework. The resulting structure is constrained by simultaneously fitting elevation, gravity, geoid and surface heat flow to reduce the uncertainties in the modelling. Further, we calculate synthetic receiver functions and surface wave dispersion curves from our velocity model. We do this to circumvent non-uniqueness of seismic tomography models and directly compare the prediction from our velocity model with the observed seismological data. Preliminary results suggest that crust is thickest beneath the Betics and thins beneath the Alboran basin within a distance of ~100 km. Farther SE, crust gradually thickens beneath the north margin of Africa, between Tell and Rif mountains over ~300 km distance. The LAB shows a similar trend though affected by the presence of the slab underneath Betics. For the Algerian domain transect, maximum crustal thickness occurs beneath the Tell-Atlas Mountains with noticeable variations across the Algerian basin, Balearic Promontory and Valencia Trough, the LAB showing a similar tendency. Comparing the modelled geometries suggests that both transects have opposite trends with the deepest Moho and LAB in the NW side of the Alboran domain transect and in the SE side of the Algerian domain transect, imposing important constrains on the geodynamic evolution of the Western Mediterranean.This is a SUBITOP (674899-SUBITOP-H2020-MSCA-ITN-2015) and MITE (CGL2014-59516) contribution. [ABSTRACT FROM AUTHOR]

Eastern Mediterranean is a unique setting where crust-mantle interractions can be studied, especially along the Hellenic and Cyprus subduction zones. Two subduction fronts are separated by N – S oriented tear from the west of Cyprus up to the Antalya Bay. The discontinuous nature of Cyprus and Hellenic subduction zones is an important question to be addressed. Furthermore, the response of the overriding crust to this complex tectonic setting has not been studied. In this study we aim to answer these questions using available seismological data.We discuss the mechanics of this transition between two subduction zones by studying the seismic velocity structure from teleseismic tomography, seismicity and the earthquake focal mechanisms in the region. There are observations that the geometry, kinematics and dynamics of the subducting plates with overlying mantle structure are correlated with the surface topography, GPS, volcanism and heat flow measurements in the region. In that regard, we computed the focal mechanism solutions of ~60 earthquakes M>4.4 between the depths of 10 and 140 km using regional waveforms. We attempt to interpret these mechanisms and seismicity distribution with an improved 3-D teleseismic P-tomographic model. The high resolution tomographic model shows the details of discontinuity between the Hellenic and Cyprus subductions. Earthquake mechanisms and the tomographic model show that in the transition zone between Hellenic and Cyprus slabs, along the Antalya Bay, a piece of the slab subducts toward northeast consistent with the prior kinematic models based on GPS velocities. In addition, some of the reverse mechanisms show intra-slab deformation and fragmentation while strike-slip earthquakes show a transitional character of the zone between two subduction fronts. In the west of Isparta Angle, we observe significant number earthquakes with normal mechanisms. The strike directions of these events are oriented E-W in the west, near Gökova Bay terminating with events with N-S directions in the east. This zone of extension sits on top of a 100 km deep low velocity zone in a tear zone of the Hellenic slab. This extensional zone and the low velocity mantle structure beneath are likely related to upwelling of astenospheric material along a slab tear. The correlation between tomographic images and geomorphology in the Isparta Angle also indicate that the active tectonics is significantly influenced by the mantle dynamics. Our study shows that the seismic structure and earthquake mechanisms reveal information about the relation between the subduction and the deformation of the Anatolian Plate. [ABSTRACT FROM AUTHOR]

Seismic methods are now part of the geophysical investigation toolbox commonly used to study the Critical Zone (CZ), not only its structure, but also its water content and flows. Acquisition setups usually consist in a collection of geophones implanted along linear profiles or arrays, at the surface of the ground excited by a portable mechanical source. Depending on the dimensions of the setups, the density of the arrays and the energy of the sources, the recorded wavefields can be analysed to image contrasts in mechanical properties of the near-surface (down to 1-100 m-depths and with 0.1-10 m-scale resolutions) using the standard equipments available for environmental applications. The most popular interpretation method is refraction tomography which consists in picking first arrivals times of the wavefield that are then inverted for pressure (P) or shear (S) waves velocity models (VP or VS, depending on the type of sources and sensors). As an alternative to S-wave refraction tomography, the recorded wavefield can also be processed to extract surface-wave dispersion data that are then inverted for VS models. VP and VS showing, by definition, partially decoupled behaviours in the presence of fluids, VP/VS or Poisson's ratio are usually estimated to image their presence in materials. We developed this approach in various contexts in the framework of the French program CRITEX. We present herein several experiments/surveys that helped describing both spatial and temporal variations of water content in the CZ, along the continuum between the saturated and unsaturated zones. Among these examples, only a few allowed the production of quantitative results (such as piezometric levels or actual saturation values). We illustrate how strong prior information about the probed CZ and/or alternative geophysical imaging techniques, geotechnical sounding or log data are mandatory to limit posterior uncertainties in VP and VS models. We also present means to estimate both traveltime and dispersion measurements errors and test their propagation in VP, VS models and derived criteria. We finally discuss the limits of discrete elastic forward problems currently used to interpret data recorded at the surface of poro-visco-elastic media with continuously varying properties. [ABSTRACT FROM AUTHOR]

In this study, we show results from ambient noise tomography at the KTB drilling site, Germany. The Continental Deep Drilling Project, or 'Kontinentales Tiefbohrprogramm der Bundesrepublik Deutschland' (KTB) is at the northwestern edge of the Bohemian Massif and is located on the Variscan belt of Europe. During the KTB project crustal rocks have been drilled down to 9 km depth and several active seismic studies have been performed in the surrounding. Therefore the KTB area is here taken as a sample for testing and verifying the potential resolution of passive seismic techniques. The aim of this study is to present a new shear-wave velocity model of the area while comparing the results to the previous velocity models and hints for anisotropy depicted by former passive and active seismological studies. We use a unique data-set composed of two years of continuous data recorded at nine 3-component temporary stations installed from July 2012 to July 2014 located on top and vicinity of the drilling site. Moreover, we included a number of permanent stations in the region in order to improve the path coverage and density. Cross correlations of ambient noise are computed between the station pairs using all possible combination of three-component data. Dispersion curves of surface waves are extracted in the 0.07 to 3 Hz frequency band and are then inverted to obtain group velocity maps. We present here a new velocity model of the upper crust, which shows that velocity variations at short periods (down to 12 km depth) correlate well with geology of the region. [ABSTRACT FROM AUTHOR]

Wave shape is recognized to be a critically important parameter in shallow water as water waves change shape as they shoal and break which influences wave orbital velocities, bed shear stresses and wave impact forces. For very large waves generated by the impact of landslides or avalanches into water, the impacts can be immense due to run-up that can be greater than 100 m above shorelines. In this study, laboratory experiments are conducted to generate waves from the impact of slides into a large wave flume. In these experiments the water depths, source volumes, and slide materials are varied, resulting in waves with a range of different amplitudes and shapes. Observations are made using a system of digital cameras and capacitance wave probes, and the wave shape is quantified by calculating the asymmetry about the vertical axis at each wave probe. The experimental results indicate that waves with positive or near-zero asymmetry in the near-field have a small influence on the maximum wave amplitude as the waves propagate along the flume. However, waves with negative asymmetry in the near-field change rapidly in shape and amplitude due to breaking until a stable state with symmetrical shape is reached. A method of quantifying the wave shape is developed and validated using the observations. This is achieved by modifying the solitary wave equation by introducing horizontal scale coefficients to account for the asymmetry. This new method could be used in combination with predictions of the maximum wave amplitude to predict more accurate boundary conditions for numerical models, which could then be applied to simulate wave propagation, improve tsunami hazard evaluation and reduce risk to human life and infrastructure in mountainous coastal regions. [ABSTRACT FROM AUTHOR]

We present a new Sino-German cooperation project in the northern Tibetan plateau:Unraveling the Dynamic Processes beneath the Northern Tibetan Plateau - PaleozoicCollision and Cenozoic Destruction of Mantle Lithosphere and Plateau Uplift. The project isfunded by the German Research Foundation (DFG) and the National Natural ScienceFoundation of China (NSFC) and involves seismic experiments as well as data analysis. Theproject aims to study fundamental questions on plateau building, processes that modify anddestroy continental lithosphere and which control lithospheric dynamics beneath orogenicbelts. The northern Tibetan Plateau features widespread Cenozoic volcanism. While themultiple terranes that constitute the Tibetan plateau become older from south to north, themagmatic events within the plateau become younger from south to north. This indicates morerecent tectonic acitivity in the northern Tibetan plateau, which is in fact expanding towardsNortheast. Seismic observations beneath Northern Tibet show poor Sn wave propagation andlow Pn wave velocities, while the shallow mantle shows low seismic velocities and strongseismic anisotropy. What is causative for those observation and what is the mode and mechanism of uplift inNorthern Tibet? Is it either caused by thickening of the Indian and Eurasian mantlelithosphere or are those observations rather explained by removal of Eurasian mantlelithosphere? What is the extend of the Indian plate beneath Tibet? Does a gap betweenIndian and Eurasian mantle lithosphere exist or do they meet beneath northernTibet? Northern Tibet is constituted of the Hoh Xil Songpan-Ganzi and the NorthQingtang terranes, which collided in the Triassic (around 250 Ma). What is thesubduction polarity of the Paleozoic Tethys ocean separating both terannes? Is theTriassic fault reactivated in Cenocoic as indicated by a Moho jump at the faultlocation? To tackle those questions we plan to deploy and analyze two linear passive-source seismicarrays in northeastern Tibet as well as to include in our analysis data from the temporalTITAN deployments, that have been conducted in Tibet from 2008 to today. Toresolve the crustal and upper mantle structure of the area we are performing surfacewave tomography using ambient noise and earthquakes and plan to jointly invertthem with receiver functions. We will present a project overview as well as firstresults. [ABSTRACT FROM AUTHOR]

At the base of Earth's mantle, just above the boundary with the core, lie two large and nearly antipodal provinces characterized by anomalously slow seismic wave speeds, termed the Large Low Shear-wave Velocity Provinces (LLSVPs). One of these structures lies beneath Africa, and the other beneath the Pacific Ocean. Accumulating evidence has increasingly revealed that the LLSVPs play an important role in mantle dynamics, most notably in that they are spatially associated with most deep-seated mantle plumes, and they coincide with the broad, antipodal upwellings of Earth's degree 2 mantle flow. In affecting large-scale convection in the mantle, and the nucleation of plumes that can fragment the lithosphere, these lowermost mantle structures may furthermore influence long-term plate motions. A key question is therefore: how stable have these features been through time? Here we review multiple independent lines of evidence that indicate that the LLSVPs have been in approximately the same position for the last 300 Ma, and possibly considerably longer. Such long-term stability of the LLSVPs remains a contentious interpretation, and so we also discuss some of the important criticism that has been raised in response to it. Given the broad implications that this discussion carries for our understanding of the nature and history of mantle convection and plate tectonics, we regard the further interrogation of LLSVP stability beyond 300 Ma to be one of the foremost imperatives in modern geophysics. The way forward is not yet clear: innovative observational methods and novel experiments together with further numerical simulations are needed to resolve the question of Earth's degree-2 stability. [ABSTRACT FROM AUTHOR]