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The unprecedented and long-lasting seismicity of Triacastela (over 25 years) attracted the interest of the research community on this stable continental region (SCR), particularly after the anomalously high 5.1 and 4.9 Mw earthquakes compared to the regional standards. The high rainfall and tide rates of this region compared to the rest of the Iberian Peninsula, in addition to the recognized existence of thermal springs and crustal fluids, motivated us to test these sources of hydroseismicity as a potential trigger mechanism for the observed seismicity in Triacastela. Based on network upgrades, we have gathered the seismic catalog in two periods for analysis (before and after year 2002). Before 2002, neither a diffusion-type earthquake migration nor any significant statistical correlation between the seismicity rates and rainfall or tides is found. After 2002, some clusters migrate to the south, suggesting the presence of fluid migration during earthquake swarms, but no diffusion-type migration is observed on longer time scales. Furthermore, we find correlation coefficients close to zero, indicating that rainfall and tides can be excluded as driving mechanisms. However, the seismic upward migration, a high b-value (1.2), and a low aftershock-productivity parameter (α = 0.9) observed in this period support the hypothesis of upward fluid migration through fracture zones. The presence of Mantellic helium-3 along the seismogenic faults and the increase of geochemical precursors in the groundwater previously to 1995 and 1997 mainshocks further support deep fluids as a source for the observed induced fluid migration seismicity in Triacastela. [ABSTRACT FROM AUTHOR]

The Cabuérniga Fault System (CFS) extends for 150 km in E-W trend along the northern divide of the Cantabrian Mountains, near the Cantabrian Sea. This fault system was reactivated several times since the Paleozoic, and displays hydrothermal activity nowadays. We present here a detailed geological map of the whole CFS and six cross-sections distributed along strike, which allowed us to unravel the kinematic history of the individual fault segments comprising the CFS. The current CFS geometry mainly results from the reactivation of E-W Variscan thrusts and NW-SE Late-Variscan strike-slip faults during the Alpine Cycle. Reactivation took place in relation to both Permian and Mesozoic pre-orogenic extension and subsequent Cenozoic shortening. The eastern end of the CFS corresponds to a N-S structure arriving at the Cantabrian coast, while the western edge connects with the E-W trending Llanera fault, leading to an Alpine fault system extending 220 km. [ABSTRACT FROM AUTHOR]

The information and seismic parameters gained from pre-instrumental earthquakes are essential to improve the seismic catalogs and hazard studies. The earthquake damage (ED) that affected architectonic elements during earthquakes (e.g. fallen walls, conjugated fractures in walls, dropped keystones in arches), and when this earthquake damage is orientated (EDO), can be used to infer seismic parameters of pre-instrumental earthquakes such as epicenter location, seismogenic source or ground motion. However, there is not a common methodology to measure this orientation damage. For example, tilting and fallen walls are some of the most used elements to infer the horizontal ground motion in non-instrumental earthquakes. Nevertheless, according to the shape of the architectonic element (a wall in this case), it has only two degrees of freedom to fall, and therefore, its azimuth does not necessarily fit with the ground motion pulse orientation. In this work, a review of the earthquake damage (ED) and effects described in pre-instrumental earthquakes is carried out. A method is also proposed, considering not only the frequency of damage orientations but also considering the uncertainty angle of each element to be damage. The ED has been classified into five groups according to the angle of uncertainty to record the pulse orientation. This method has been checked taking advantage of recent earthquakes with a good instrumental record of the ground motion pulse, and also tested modeling different scenarios with different pulse orientations. This method, that takes into account the uncertainty angles, is a reliable method to calculate the EDO and back-calculate the ground motion pulse orientation in pre-instrumental earthquakes in absence of more accurate modern instrumental records. This method can also be useful for seismic risk assessment and restoration and protection of historical heritage. [ABSTRACT FROM AUTHOR]

The NW Iberian Peninsula is an intraplate region with significant seismicity, but it has rarely been studied. Despite the increase in seismicity during recent years, which has even forced changes to the building codes, a comprehensive statistical analysis of this seismicity has not been carried out. Thus, this study aims to characterize seismicity clusters on an intraplate region, based on comprehensive qualitative and quantitative analysis. The b value of the Gutenberg–Richter law is estimated and the Epidemic Type Aftershock Sequence model is employed. Additionally, qualitative analysis is carried out using the Mogi classification, and the results of this work are compared with those of other statistical studies in the literature. We identify clustered seismic activity in the NW Iberian Peninsula, which is classified into 18 swarms and eight sequences. A high b value and low efficiency of aftershock generation are characteristic of the swarms. These parameters, along with the similarities to other regions, point to fluid migration as the swarm seismic source mechanism. Earthquakes of higher magnitude than swarms and a b value close to 1 define the sequences of this region. The statistical results in sequences (high k, c, and p values) and the similarity to other regions would indicate a mix of tectonic origin and aseismic processes (such as fluid migration or slow slip events) as the driving force of seismic sequences. The presence of crustal fluids associated with fault activity in the NW Iberian Peninsula also supports the hypothesis of fluid migration as the source of seismic events. [ABSTRACT FROM AUTHOR]

Abstract The Pyrenean-Cantabrian Orogen arose through the collision of the Iberian and Eurasian plates, mostly in Cenozoic times. This orogen comprises two main mountain ranges, the Pyrenees to the east, and the Cantabrian Mountains to the west. To date, the early Alpine tectono-sedimentary phases preserved in the Cantabrian Mountains, of Permian and Triassic age, have been considered independently from the same phases in neighbouring basins of SW Europe, and even from the eastern part of the same orogeny (the Pyrenean orogeny). In consequence, the beginning of the Alpine cycle in the Cantabrian Mountains has been interpreted within a specific geodynamic context, far from the general evolutionary phases of the western Peri-Tethys basins. Through detailed field work, including geological mapping, sedimentology, lithostratigraphy and petrology of volcanic rocks, and new palaeontological data, here we define several new lithostratigraphical formations and five new tectono-sedimentary cycles (TS I-V) for the initial phases of evolution of the Mesozoic Basque-Cantabrian Basin, interrupted by periods of tectonic stability. To complete this information, we include data from an onshore borehole (Villabona Mine) and two offshore boreholes constrained by 2D reflection seismic profiles acquired in the North Iberian continental platform. The main tectono-sedimentary cycles, related to the deposition of five major identified lithostratigraphic units, can be described as follows: TS I (late Gzelian-early Asselian), relating to the late Variscan deformation and preserved in a single outcrop in all the Cantabrian Mountains (San Tirso Formation). This formation is constituted by medium-distal alluvial fan deposits in which humid intervals predominate, forming some thin coal beds. TS II (Asselian-Sakmarian), a post-Variscan extensional phase with associated calc-alkaline magmatism, represented by profuse volcanic and volcanosedimentary intercalations in the early Permian sedimentary basins (Acebal Formation) and small plutons in surrounding areas. TS III (Kungurian), or reactivation of the post-Variscan extension leading to alluvial and lacustrine carbonate sedimentation in arid climate conditions, which do not change during the rest of the Permian and Triassic periods (Sotres Formation). A generalized karstification in the basin represents the end of Permian deposition, followed by an interruption in sedimentation longer than 30 Myr. The Permian tectono-sedimentary cycles (TS II and TS III) are contemporary with Variscan belt collapse and the basins are controlled by extensional reactivation of N E -SW and E-W Variscan structures, and NW-SE late Variscan structures. TS IV (late Anisian–middle Carnian), renewed sedimentation in more extensive basins, precursors of the great Mesozoic Basque-Cantabrian Basin. This cycle is represented by fluvial deposits (Cicera Formation, or Buntsandstein facies), which are interrupted by the first Mesozoic marine ingression (Rueda Formation, or Muschelkalk facies). TS V (Norian-Rhaetian), or shallow marine carbonate deposits (Transición Formation) related to increasingly compartmentalized sub-basins, controlled by normal faults. This final TS is broadly connected with different basins of the western Peri-Tethys domain. The identification of units TS I-V in the Cantabrian Mountains along with the volcanic character of TS II, all indicate the development of a common post-Variscan to early Alpine tectono-sedimentary evolution for the whole Pyrenean-Cantabrian realm. Highlights • The beginning of the Alpine cycle in the Cantabrian Mountains has been erroneously interpreted within a specific geodynamic context far from the well-known general evolutionary stages of same-age western Peri-Tethys basins. • Through detailed multidisciplinary field work, including new palaeontological data, this study defines new lithostratigraphical units and five new tectono-sedimentary cycles (TS I-V) in the Cantabrian Mountains. • The end of the Permian deposition in the Cantabrian Mountains is represented by a karstification of palaeogeographic significance. • As our main contribution to the field, the TS I-V units defined point to a common post-Variscan to early Alpine tectono-sedimentary evolution for the whole Pyrenean-Cantabrian realm. [ABSTRACT FROM AUTHOR]

Despite that earthquakes in stable continental regions (SCR) often cause more damage than interplate seismicity, they remain poorly understood. This is mainly because of the lower rate of intraplate seismicity and because of its different behaviour compared to the better-known seismicity at the plate boundary. Understand the characteristics of the intraplate seismicity is a challenge for the seismic risk studies. We study and characterise an SCR (NW Iberian Peninsula), which not only registers moderate instrumental intraplate seismicity, but also important historic seismicity and paleoseismic activity. To tackle some of the difficulties posed by intraplate seismicity, we analyse a wide and multidisciplinary data set (e.g., geological structures, seismicity, focal mechanisms, and geophysical data). Seismicity in this region is not associated with an old rift, but with inherited faults widely distributed throughout the region with a great variety of orientations. The reactivation kinematics of these faults are coherent with the current regional stresses. Instrumental seismicity is not associated with the large active faults nor with crustal limits. Seismicity is mainly clustered in swarms and sequences. Although seismic swarms present lower magnitudes, they are the most common. Based on swarms' characteristics (high b-values, upward spatiotemporal migration), reported mantellic CO2 in some thermal springs, and the reactivation of inherited steeply-dipping faults, we propose the migration of deep fluids through steeply-dipping fractured areas as the cause of the intraplate seismicity. These processes could increase the pore pressure and decrease the stresses necessary for the fault rupture in a fault-valve behaviour. In general, in intraplate context, the important control in the seismicity of the inherited fault systems favourable oriented under the current stress tensor is observed, and also the need for mechanisms that can decrease the effective stress for the fault ruptures. Mechanisms as hydrothermal fluids in arterial faults with fault-valve processes has been identified as an effective driver of intraplate seismicity, playing an important role in stability of tectonic faults. The large number and variety of these faults, that share the low strain rates in intraplate polyorogenic context, may explain the different characteristics of these intraplate regions compared with the interplate regions, as the "unanticipated" behaviour, variety of kinematics, the long quiescence periods without seismicity associated and erosion obliterating their morphotectonic expression. • Seismogenic faults are inherited fault systems reactivated under current stress field. • Intraplate characteristics due to the large number and variety of inherited faults. • Need for mechanisms that can decrease the effective stress for the fault ruptures. • Deep fluid migration in subvertical faults decrease effective stress. • Fluids migration in a fault-valve behaviour responsible for seismic swarms. [ABSTRACT FROM AUTHOR]

Studies to provide information concerning seismic parameters and seismic sources of historical and archaeological seismic events are used to better evaluate the seismic hazard of a region. This is of especial interest when no surface rupture is recorded or the seismogenic fault cannot be identified. The orientation pattern of the earthquake damage (ED) (e.g., fallen columns, dropped key stones) that affected architectonic elements of cities after earthquakes has been traditionally used in historical and archaeoseismological studies to infer seismic parameters. However, in the literature depending on the authors, the parameters that can be obtained are contradictory (it has been proposed: the epicenter location, the orientation of the P-waves, the orientation of the compressional strain and the fault kinematics) and authors even question these relations with the earthquake damage. The earthquakes of Lorca in 2011, Christchurch in 2011 and Emilia Romagna in 2012 present an opportunity to measure systematically a large number and wide variety of earthquake damage in historical buildings (the same structures that are used in historical and archaeological studies). The damage pattern orientation has been compared with modern instrumental data, which is not possible in historical and archaeoseismological studies. From measurements and quantification of the orientation patterns in the studied earthquakes, it is observed that there is a systematic pattern of the earthquake damage orientation (EDO) in the proximity of the seismic source (fault trace) (<10 km). The EDO in these earthquakes is normal to the fault trend (±15°). This orientation can be generated by a pulse of motion that in the near fault region has a distinguishable acceleration normal to the fault due to the polarization of the S-waves. Therefore, the earthquake damage orientation could be used to estimate the seismogenic fault trend of historical earthquakes studies where no instrumental data are available. [ABSTRACT FROM AUTHOR]

The role of inherited weaknesses in metamorphic basements with respect to the geometry and tectonic evolution of subsequent orogens formation forms a cornerstone of structural reconstructions, especially in non-inverted orogens with old Variscan basements. In this study, we analyse the geometry, kinematics, and tectonic evolution of the complex western termination of the Alpine Pyrenean–Cantabrian orogen using an integrated approach based on analogue modelling, constrained by structural mapping and geochronology, to provide new insights into the role of pre-existing structures and the shift in the orientation of the stress field. Our results demonstrate that pre-existing structures are necessary to explain the complex western termination, which does not follow the same tectonic architecture as the rest of the orogen. The reason for this is the different orientation of the pre-existing Variscan structures in this area, which do not follow the general E–W trend. These western structures (including NNE–SSW and NW–SE strike-slip fault systems and a greater number of E–W thrusts) accommodate the shortening, but have a less favourable orientation. The reactivation of the NNE–SSW strike-slip faults and the southern E–W thrusts in the recent stages indicates a late intraplate tectonic regime, mainly following the shift of the Shmax (from N–S to NNW–SSE) which occurred when the convergence between the Iberian, Eurasian, and African plates changed. • NW Iberia Variscan structures control the lateral termination of Alpine orogen. • Multiple inherited structures accommodated Alpine shortening in wider region. • The wide variety of structure orientations generate more complex tectonic models. • Iberian plate convergence shifts, reactivated structures in intraplate regimen. [ABSTRACT FROM AUTHOR]

Regeneration after landslides is how an ecosystem recovers itself following a landslide event. Natural systems can recover and regenerate over time. The main objective of the current work is to identify and characterise the regeneration pattern after a great landslide event in 2013 in the Guerrero state (Mexico) using remote sensing, geographic information system (GIS), and machine learning techniques. Remarkably, the authors consider normalised difference vegetation index (NDVI) as a proxy of part of this "regeneration" in the present work. A first methodology attempt presented here was to monitor and characterise the "regeneration" after severe landslide events. First, the authors calculated and identified the (1) losses, (2) speed and (3) recovery time through a continuous change detection and classification algorithm (CCDC) in Google Earth Engine (GEE) from a NDVI-Landsat time series (from 1984 to 2021). Second, these three factors were introduced as variables in a not supervised machine-learning model to get 5 clusters that characterise the different regeneration patterns followed from 2013 to 2021 in the landslide zones. Finally, we studied 16 variables like elevation, slope, or soil pH. The authors included those variables in a supervised machine learning classification to find the most important main drivers related to the NDVI regeneration of the landslide areas. The results showed that the cluster called Group 0 had a low loss of NDVI value, speed and medium recovery time. Group 1 showed a medium–high loss, high speed and low recovery time. Group 2 reached a high loss, a low speed, and an increased recovery time. Group 3 with a medium loss, a medium speed, and a low recovery time. Finally, Group 4 with a high loss of NDVI, a medium speed, and a medium recovery time. Distance to the edge of the landslide, precipitation, land cover type and lithology are highlighted as the main drivers in landslide regeneration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lateritic clays occur in fault contact with granites in a Cenozoic basin. • Geochemical data indicates an allochthonous mafic source for the lateritic clays. • Hydrothermal fluids interacted with the lateritic clays and the granites. • Faults had extensional component and were re-activated with inverse strike-slip. • Faults were not effective seals for the hydrothermal fluids. Continental basin evolution can be influenced not only by tectonic activity, but by hydrothermal and weathering processes. This is displayed on the basement rocks (granites and xenoliths) and sedimentary cover (clays, sands and conglomerates) in the Cenozoic Ferreira basin of NW Spain. In this study, we applied petrological, geochemical and structural proxies to investigate a red clay unit and adjacent granitic basement rocks in a fault contact. Red clays have a lateritic composition (SiO 2 : 38–42 wt%, Fe 2 O 3 : 13–20 wt% and Al 2 O 3 : 24–29 wt%) with moderate to high contents in V (267 – 324 ppm) and Ni (46–71 ppm), and are characterized by (La/Yb) n and TREE that vary from ∼5 to 12 and ∼55 to 110 ppm, respectively. The basement rocks are peraluminous biotite granites (A/CNK: 1.12–13.57) with (La/Yb) n and TREE that vary from 7.7 to 27.42 and from 82.79 to 244.64 ppm, respectively. The xenoliths are peraluminous shales (A/CNK: 3.48–4.48) with (La/Yb) n and TREE varying from 7.66 to 11.10 and from 228.61 to 344.42 ppm, respectively. This geochemistry indicates that the lateritic red clays come from residual weathering of mafic ± intermediate rocks. They are interpreted to have been generated under the tropical climate conditions in the Late Cretaceous (∼70 Ma). Afterwards red clays were remobilized in subsequent tectonic events (Alpine), deposited in faulted grabens, and together with adjacent basement granites, affected by hydrothermal events that caused element mobility (e.g., REE leaching and Ce positive anomalies). Fault reactivations, under strike-slip stresses with a reverse component, channelized these hydrothermal fluids and uplifted part of the landscape. This uplift is interpreted as the trigger of an erosional regime that affected the lateritic red clay unit in the Ferreira basin. The conclusions of this study highlights the important interplay of different geological processes in small continental basins. [ABSTRACT FROM AUTHOR]

We report the results of a multidisciplinary study of the early Permian (Artinskian–Kungurian) Sotres Formation of northern Spain integrating sedimentology, palaeosols, mineralogy, stable isotopes, palynology, ichnology and tectonics. This continental unit was deposited in the near-equatorial Peri-Tethyan Cantabrian Basin. Having developed in the middle of the Variscan fold belt, it is preserved within the present-day Cantabrian Mountains. Three subunits are recognised in the Sotres Formation based on tectono-stratigraphic and sedimentological data: a lower alluvial subunit, a middle carbonate lacustrine subunit, and an upper palustrine subunit. Multidisciplinary results reveal an upward change in climate from humid-subhumid conditions at the base of the formation (Artinskian) to semi-arid and arid conditions at the top of the formation (Kungurian), which may reflect global deglaciation near the end of the Late Paleozoic Ice Age and a probable northward migration of the Intertropical Convergence Zone. This general upward warming/drying climate trend was interrupted by a short-lived interval of monsoon conditions in mid-Kungurian times, which may have coincided with a pulse of global cooling. Our findings are in agreement with the climate trends reported for other central Pangaean basins. Rising CO2 levels may have been a driving factor for climate transition during this time interval. However, in our study area, which lies within the active central Variscan orogenic belt, tectonic conditions must have also played a role in driving climate change. [ABSTRACT FROM AUTHOR]

Abstract Rift zones are fundamental features in oceanic island volcanoes, although their origin is still controversial, especially at the Canary Islands where the role of volcanic spreading is under debate. For this reason, we have performed a field study of > 400 dykes at 20 outcrops in the Lower Old Edifice and 2 outcrops of the Upper Old edifice of La Gomera Island, identifying different dyke swarms. We propose the development of an unnoticed E-W volcanic rift (Hermigua Rift) restricted to the Lower Old Edifice East flank, with up to 25% of extension and structural characteristics compatible with the spreading of the edifice over a basal weak decollement. Contemporaneously a dyke swarm of outward-dipping dykes intruded at the W-SW zones, indicating a progressive radial sliding of the edifice. This asymmetric volcano structural pattern suggests that volcano stresses were predominately local in origin, probably related to the buttressing effect of the neighbor contemporaneous Roque del Conde edifice (Tenerife Island). Additionally, we have deduced two different rift zones (NW-SE Enchereda and N-S Erque rifts) during the growth of the Upper Old Edifice, evidencing that La Gomera rifts were dynamic evolving structures. The structure and regional setting of the Upper Old Edifice rifts suggest a change to a predominance of regional stresses. Our results have implications for the understanding of the origin and evolution of rifts at oceanic island volcanoes, since: 1) confirm a principal role for volcanic spreading processes; 2) support that the location of neighbor volcanic loads strongly influences rifts development; and 3) suggests, in some situations, a possible main role for the regional stress field. Highlights • We identify several unnoticed rift zones at Old Volcanic Edifice of La Gomera by their underlying coherent dike complexes. • An unnoticed E-W structure (Hermigua Rift) developed at the east flank of the Lower Old Edifice with up to 25% of extension. • Contemporaneously a singular swarm of outward dipping dikes developed at the volcano west flank. • Asymmetric volcano structural pattern suggests that volcano stresses were local in origin related to the volcano spreading. • The neighbour contemporaneous Roque del Conde edifice (Tenerife Island) produced a buttressing effect. • Two new rift zones (NW-SE Enchereda and N-S Erque rifts) developed during the growth of the Upper Old Edifice. • Rifts of the Old Volcanic Edifice of La Gomera were dynamic evolving structures. • The character of the Upper Old Edifice rifts suggest a change to a predominance of regional stresses during its growth. [ABSTRACT FROM AUTHOR]

In the Cuesta del Rahue area, located in the Precordillera Neuquina (northern Argentine Patagonia), late Paleozoic turbiditic rocks with maximum depositional age of ca. 389 Ma were affected by three orogenic events. The oldest orogenic event is the Chanic orogeny (Late Devonian–early Carboniferous) that is characterized by folds with NNE vergence. This deformation is developed in low-grade to very low-grade metamorphic conditions, which allowed the development of a slaty/rough cleavage. The main Chanic structure is an asymmetric fold with a large normal limb tilted by the more recent orogenic events. The characteristics of the deformation and metamorphism allows us to assign the Cuesta del Rahue outcrop to the external hinterland of the western wedge of the Chanic orogen. Early to late Carboniferous igneous rocks intruded the Paleozoic rocks of the Cuesta del Rahue area and crosscut the Chanic structures. After the Chanic orogeny, the Gondwanan orogeny (late Carboniferous–early Permian) took place. The main structures of the Gondwanan orogen are thrust and related folds with SSW vergence that fold the large Chanic normal limb and also affect Carboniferous igneous rocks. The Gondwanan deformation was developed under non-metamorphic conditions, and Permian igneous rocks crosscut the Gondwanan structures. Mesozoic regional extension related to the beginning of the Andean cycle and the formation of the Neuquén Basin gave rise to normal faults and small-scale extensional folds. Finally, the Andean orogeny, developed during the Cenozoic in the study area, also affected the Cuesta del Rahue Paleozoic rocks, with the development of compressional structures related to the Aluminé thrust and fold belt. The main Andean structure in the study area is the NW–SE Rahue fault, which links the E–W Piedra Santa tear fault with the NNE–SSW Catán Lil reverse fault. The Rahue fault has a SW tectonic transport direction. It uplifted the Cuesta del Rahue area and placed Paleozoic rocks on top of Mesozoic and Cenozoic rocks. The Piedra Santa fault partially reactivated the Huincul right-lateral and left-lateral Chanic transverse faults that define the southern end of the doubly vergent Chanic orogen, giving rise to the current Huincul lineament. • New insights on the evolution of the Paleozoic basement of the Andes in the southern end of the Cuyo Sector are presented. • In the Cuesta del Rahue outcrop the Paleozoic basement is a turbiditic succession, Middle to Late Devonian in age. • The Cuesta del Rahue is located on the southern end of the western wedge of the Chanic orogen. • The Paleozoic rocks were deformed by the late Paleozoic Chanic and Gondwanan orogenies and the Cenozoic Andean orogeny. • Th Huincul lineament is a wrench fault, limiting by the south the Chanic orogen, partially reactivated during the Gondwanan and Andean orogenies. [ABSTRACT FROM AUTHOR]

During the late Carboniferous–middle Permian, the basement of the Chilean Coastal Cordillera was deformed by the Gondwanan Orogeny, developed by the subduction of the Paleo-Pacific plate under Gondwana from the early Carboniferous. In the Maule sector (35.4°S), the following metamorphic rock units are distinguished: (i) Western Series, formed by metapelites, metabasites, metacherts, metaconglomerates, and marbles, mixed in a subduction channel, with probably ages between the Cambrian and the Carboniferous; (ii) Eastern Series, consisting of metasediments of a fore-arc basin, Carboniferous in age. In the Eastern Series two units are recognized in terms of lithology and deformation style: the Eastern Pelitic Series and the Eastern Sandy Series. Three Gondwanan deformation episodes have been distinguished, affecting both series unequaly. In the Western Series, D1 structures consist of a foliation (S 1) developed under high-pressure and low-temperature conditions, while in the Eastern Series it comprise tight east-verging folds, with the associated S 1 developed under low PT metamorphic conditions (greenschist facies). D2 structures are only present in the Western Series and Eastern Pelitic Series and represent the exhumation of the accretionary prism and its emplacement to the east over the fore-arc basin, with the development of east-verging recumbent folds and a thick shear-zone. Difficulties in the propagation of the deformation by the presence of the Coastal Batholith to the east led to the development of the D3 deformation event, only well developed in the Eastern Sandy Series, and represented by the Los Tablones Back-thrust and associated folds, as well as N–S open right folds formed under low PT metamorphic conditions. • New data on the lithology, structure and metamorphism of the Paleozoic rocks of the Chilean Coastal Range are presented. • Paleozoic rocks of the Maule River were deformed during the Gondwana orogeny under different metamorphic conditions • The Western Series deformed in HP metamorphic conditions during D1 in the subduction channel and was exhumed by an east-directed thrust during D2 • Structures D1, D2 and D3 of the Oriental Series were developed under LP-LT metamorphic conditions. The D1 and D2 have East vergence and the D3 West [ABSTRACT FROM AUTHOR]

The Hope fault is the most active and southernmost splay of the Marlborough fault system in the northern South Island of New Zealand. The fault consists of five geometrically defined segments. We used trenching to acquire paleoseismic data and radiocarbon dating of faulted late Holocene sediments on the Hurunui segment of the Hope fault to derive an earthquake chronology that extends from the historic 1888 Mw 7.1 Amuri earthquake to ca. 300 C.E., thereby providing the longest chronologic record of earthquakes on the Hope fault to date. Earthquake event horizons were identified by upward fault terminations, colluvial wedges, unconformities, and/or progressive folding of shutter basin deposits. Six earthquakes identified at C.E. 1888, 1740-1840, 1479-1623, 819-1092, 439-551, and 373-419 indicate a mean recurrence interval of ~298 ± 88 yr, with successive median interevent times ranging from 98 to 595 yr. The large variance in interevent times with respect to mean recurrence interval is explained by (1) possible coalescence of rupture overlap from the adjacent Hope River segment onto the Hurunui segment at our study site (including the 1888 Mw 7.1 Amuri earthquake, sourced primarily from the Hope River segment), which results in apparently shorter interevent times at the study site compared to mean recurrence intervals from adjacent fault segments, (2) possible earthquake temporal clustering on the Hurunui segment, which could result in interevent times that are significantly shorter or longer than interevent times and mean recurrence intervals predicted by a periodic earthquake rupture model, and/or (3) "missing" events, which could result in interevent times and mean recurrence intervals at the study site that are longer than the actual mean recurrence interval. While we cannot exclude option 3 as a possibility, we prefer options 1 and 2 to explain earthquake chronologies and rupture behavior on the Hurunui segment of the Hope fault, given the detailed nature of our geologic and chronologic investigations. By demonstrating that the 1888 Amuri earthquake propagated through a proposed segment boundary, we provide the first evidence for coseismic multisegment ruptures on the Hope fault. In contrast, the penultimate earthquake ruptured the Hurunui segment at 1740-1840 C.E. with no known rupture of the Hope River segment. Paleoearthquake records near geometrically complex segment structural boundaries on major strike-slip faults may show temporal recurrence distributions resulting from earthquake ruptures that variably arrest or propagate through proposed segment boundaries. We note that earthquake recurrence along major strikeslip plate-boundary faults may vary between more periodic and more episodic end members, even on adjacent, geometrically defined segments. [ABSTRACT FROM AUTHOR]

Metallic mining wastes are a crucial environmental concern because of the accumulation and emission of toxic elements. The abandoned San Quintín mine tailings, from the exploitation of galena and sphalerite (Puertollano mining district, Spain), are surrounded by farmland and are crossed by the European Cultural Itinerary known as the “Don Quixote Route”. Geophysical, mineralogical and geochemical techniques have been applied to determine the geometry and composition of mine ponds and the possible occurrence of AMD that could entail ecosystem and human risks. Seven electrical resistivity tomography profiles were surveyed, and re-worked tailing samples of two ponds, five soil samples, nine water samples and gaseous mercury emissions were analyzed. Both mine ponds are ~ 8 m deep and overlie Quaternary colluvial sediments deposited over Precambrian metasediments. The pond infilling is mainly composed of quartz and clay minerals, and minor amounts of gypsum and sulfides, with significant As, Cd, Hg, Pb, Sb and Zn contents. This metal emission source affects the underlying colluvial sediments and high Hg and Pb contents have also been found in nearby agricultural soils. AMD has been identified, but metal contamination in the stream that borders the tailings is below the USEPA's recommended limits. Although gaseous mercury emissions from a cinnabar stockpile increase in summer, the measured levels do not reach the WHO's recommended limit. The Enrichment Factor and I geo indexes for As, Cd, Hg, Pb, Sb and Zn indicate strong to extreme contamination in the mine ponds and moderate contamination in the colluvial sediments/metasediments. Aeolian dispersion is the most important contaminant agent. The surrounding soils show strong to extreme levels of Hg and moderate to extreme levels of As, Cd, Pb and Sb. Restoration of these abandoned wastes is recommended to reduce the health risks for residents and tourists due to this aeolian contaminant dispersion. [ABSTRACT FROM AUTHOR]

One of the most important geological effects generated by the seismic events of Emilia Romagna (Italy, 2012) was the liquefaction. The first earthquake took place on 20th May (5.9 M w ) and generated liquefaction in the locality of San Carlo, mainly recorded as large fissure sand volcanoes. Detailed stratigraphic and sedimentology analyses of these sand bodies indicated the assemblage of rhythmic normal graded beds of sand for many individual sand volcanoes. This is interpreted as repeated individual sand extrusions generating polygenetic sand blows for a single earthquake. This original analysis, made for first time in a case of extensive seismic liquefaction, indicates that the different pulses sand extrusion occurred after seismic shaking, and therefore no related to the cyclic seismic shearing stimulated by surface seismic waves. Underground liquefaction of shallow sandy layers and ground cracking, assisted by relevant lateral spreading, promoted water and sand ejections (E–W direction). Localised and repeated ground subsidence and bulging supported by the ejection of the underlying fluidized sediments feedback transient ground undulations and repeated sand ejections. The unstable undulating behaviour of the ground reinforced and sustained the liquefaction process through time after the seismic shaking, leading the occurrence of polygenetic sand volcanoes. In summary, the seismic liquefaction is the starting point of the process, although only if these sand ejections could promote the instability of the ground since underground sand depletions feedback the liquefaction process through time. The process stops when the hydrostatic balance is recovered in the affected zone. [ABSTRACT FROM AUTHOR]

Pleistocene fluvial incision acceleration resulting in narrow and deeply entrenched valleys has been widely described and is generally attributed to uplift rate increase or greater climatic severity. In this paper, the long-term downcutting pattern of the Upper Ebro River and driving mechanisms are assessed, and we reconstruct the valley incision recorded by an outstanding sequence of 22 river terraces. Dating of 8 fluvial levels by means of the ESR, TCN, and OSL techniques, spanning the last 1.2 Ma, reveals a long-term incision deceleration pattern. The estimated age-incision model indicates a decrease in the incision rates, showing a long-term deceleration during the final Early Pleistocene (from 0.42 to 0.18 m/ka), and a tendency towards a steady state or base level stabilization from the Middle Pleistocene (0.15–0.03 m/ka) to the Late Pleistocene (0.03 m/ka). This incision pattern does not support climate change as a long-term incision-acceleration driver by itself, demonstrating the need for base level lowering effects to have operated. Upper Ebro deceleration incision is explained by the headward attenuation of the incision wave induced by the opening of the Ebro Cenozoic Basin in a geodynamic context characterized by an absence of significant uplift over the last million years. This trend could have changed the aggressor-victim roles of the rivers involved in fluvial captures at the drainage divide. The documented incision deceleration pattern differs from that reported for other valleys in the Iberian Peninsula, suggesting that the degree of maturity of the fluvial systems depends on their relative position with respect to the capture point, in addition to tectonic and lithostructural factors. In the Late Pleistocene-Holocene, a short-lived incision rate increase is recorded, corresponding to the last terrace dissection phase, during the transition from the last glacial MIS 2 to the interglacial MIS 1. • Incision acceleration is widely reported during Pleistocene valley entrenchment. • However, the Upper Ebro valley contains a complex sequence of fluvial terraces • which were dated within the last 1.2 Ma using ESR, TCN and OSL techniques • and indicate an incision deceleration pattern. • This suggests that the river incision is tending to a steady state. [ABSTRACT FROM AUTHOR]

In the northern Iberian Peninsula, the Pyrenean-Cantabrian orogenic belt extends E-W for ca. 1000 km between the Atlantic Ocean and Mediterranean Sea. This orogen developed from the collision between Iberia and Eurasia, mainly in Cenozoic times. Lower-middle Permian sediments crop out in small, elongated basins traditionally considered independent from each other due to misinterpretations on incomplete lithostratigraphic data and scarce radiometric ages. Here, we integrate detailed stratigraphic, sedimentary, tectonic, paleosol and magmatic data from well-dated lithostratigraphic units. Our data reveal a similar geodynamic evolution across the Pyrenean-Cantabrian Ranges at the end of the Variscan cycle. Lower-middle Permian basins started their development under an extensional regime related to the end of the Variscan Belt collapse, which stars in late Carboniferous times in the Variscan hinterland. This orogenic collapse transitioned to Pangea breakup at the middle Permian times in the study region. Sedimentation occurred as three main tectono-sedimentary extensional phases. A first phase (Asselian-Sakmarian), which may have even started at the end of the Carboniferous (Gzhelian) in some sections, is mainly represented by alluvial sedimentation associated with calc-alkaline magmatism. A second stage (late Artinskian–early Kungurian), represented by alluvial, lacustrine and palustrine sediments with intercalations of calc-alkaline volcanic beds, shows a clear upward aridification trend probably related to the late Paleozoic icehouse-greenhouse transition. The third and final stage (Wordian-Capitanian) comprised of alluvial deposits with intercalations of alkaline and mafic beds, rarely deposited in the Cantabrian Mountains, and underwent significant pre- and Early Mesozoic erosion in some segments of the Pyrenees. This third stage can be related to a transition towards the Pangea Supercontinent breakup, not generalized until the Early/Middle Triassic at this latitude because the extensional process stopped about 10 Myr (Pyrenees) to 30 Myr (Cantabrian Mountains). When compared to other well-dated basins near the paleoequator, the tectono-sedimentary and climate evolution of lower-middle Permian basins in Western and Central Europe shows common features. Specifically, we identify coeval periods with magmatic activity, extensional tectonics, high subsidence rates and thick sedimentary record, as well as prolonged periods without sedimentation. This comparison also identifies some evolutionary differences between Permian basins that could be related to distinct locations in the hinterland or foreland of the Variscan orogen. Our data provide a better understanding of the major crustal re-equilibration and reorganization that took place near the equator in Western-Central Europe during the post-Variscan period. • The beginning of the Iberian Variscan orogenic collapse is late Carboniferous in the hinterland and early Permian towards the foreland. • Variscan orogenic collapse is associated with calc-alkaline magmatism that shifts to alkaline magmatism in middle Permian times. • The beginning of the Alpine cycle of sedimentation in the whole Pyrenean ranges occurred as three main Permian tectono-sedimentary extensional phases. • The Permian tectono-sedimentary evolution of the Pyrenean ranges shows common features to the ones of Central and W Europe basins. [ABSTRACT FROM AUTHOR]

Landslides are recognized as high-impact natural hazards in different regions around the world; therefore, they are extensively researched by experts. Landslide inventories are essential to identify areas that are likely to be affected in the future, thereby enabling interventions to prevent loss of life. Today, through combined approaches, such as remote sensing and machine learning techniques, it is possible to apply algorithms that use data derived from satellite images to produce landslide inventories. This work presents the performance of five machine learning methods—k-nearest neighbor (KNN), stochastic gradient descendent (SGD), support vector machine radial basis function (SVM RBF Kernel), support vector machine (SVM linear kernel), and AdaBoost—in landslide detection in a zone of the state of Guerrero in southern Mexico, using continuous change maps and primary landslide factors, such as slope angle, terrain orientation (aspect), and lithology, as inputs. The models were trained with 2/3 of ground truth samples of 671 slidden/non-slidden polygons. The obtained inventory maps were evaluated with the remaining 1/3 of ground truth samples by generating a confusion matrix and applying the Kappa concordance coefficient, accuracy, precision, recall, and F1 score as evaluation metrics, as well as omission and commission errors. According to the results, the AdaBoost classifier reached greater spatial and statistical coherence than the other implemented methods. The best input layer combination for detection was the continuous change maps obtained by the linear regression and image differencing detection methods, together with the slope angle, aspect, and lithology conditioning factors. [ABSTRACT FROM AUTHOR]