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The Valles Marineris canyon system in Mars shows large landslides across its walls, which can be 40 km wide and up to 60 km long, with fall scarps height as high as 7 km. These landslides were produced through a large mass movement at high speed by gravity across the trough floor. Although the triggering factors are unclear, several mechanisms have been proposed as, among others, large amounts of subsurface water, quake produced through normal faulting close to the canyon walls, and meteoritic impacts. In this work we examine the limit equilibrium slope stability of three landslides (placed respectively at Ius, Candor, and Melas Chasmata), which can be considered representative, with the aims of constraining their formation conditions. Our results suggest that external factors (as high pore fluid pressure, seismic loading or rock mass disturbance) do not seem necessary for the failure of slopes if they are composed of unconsolidated materials, while high pore water pressure or ground acceleration are needed to trigger slides in slopes composed of strong basaltic-like materials. Moreover, the presence of sub-surface ice would contribute to slope stability. As a whole, our findings point to ground shaking due to meteorite impacts as the main triggering force for most landslides in the Valles Marineris. [ABSTRACT FROM AUTHOR]

• Mineralogy and geophysics used to describe depositional sequences of Guadiana Basin. • Illite, smectite + palygorskite and kaolinite enrichment image 3 depositional sequences. • Depositional sequences exhibit distinct electric resistivity imaging. • Data integration unravels Guadiana Basin formation and the role of Alpine tectonics. In the Iberian Peninsula, Alpine tectonics built several Cenozoic basins that were mainly filled with continental deposits. The Guadiana Basin is located halfway between two of the most important Cenozoic basins of the SW of Spain, the Tajo and the Guadalquivir basins. In this paper, both geophysical and mineralogical studies have been carried out in order to establish the lithostratigraphy of the Guadiana basin. A combination of electric resistivity properties and variations in clay mineral assemblage content of the basin infill was used to identify several depositional sequences within the Cenozoic deposits of the basin. Three depositional sequences, DS1, DS2 and DS3 characterized by differentiated clay content and mineral assemblages were distinguished. The lower depositional sequence, DS1, consists of reddish siltstones and clays that scarcely crop out in the basin. Clay content of the <2 μm fraction is dominated by illite averaging 60% of the total clay content, with kaolinite and a few amount of smectite. DS2 deposits lie unconformably over DS1 and the Variscan basement and consist of a siliciclastic succession where carbonate units occur at bottom and at the top of the depositional sequence. Smectite dominates throughout the entire succession except in the basal carbonate unit where up to 70% of palygorskite is found. In the younger sequence DS3, kaolinite is the dominant clay mineral. Electrical resistivity imaging helped in the physical characterization and horizontal and vertical distribution of each unit and provided good insight on the structure of the Guadiana Basin, allowing to infer the basin structure due to high resistivity contrast between the basement and the sedimentary rocks. In addition, in areas where the lower sedimentary units do not crop out, and borehole information is not available, the geophysical response of the resistivity units imaged can be used to infer the corresponding depositional sequence. The joint interpretation of the clay mineral assemblages and geophysical properties of the sedimentary units showed to be a useful tool to gather a reliable identification of depositional sequences in basins characterized by scarcity of good outcrops, lack of borehole information and similarity of sedimentary rocks. This is very important to properly correlate the different sedimentary units mapped as well as to infer the basin structure and its evolution through time. [ABSTRACT FROM AUTHOR]

The low frequency of large destructive earthquakes in the Eastern Betics (SE Iberian Peninsula), not recorded in the instrumental seismic catalog, complicate the estimation of the maximum ground motion that could be reached. Knowing the characteristics and behavior of these large seismic ruptures is crucial for the study of seismic hazard. In this work, we have used a physics-based earthquake simulator to generate a 100 kyr catalog of seismic ruptures associated with seismogenic faults bordering the quaternary Guadalentin and Bajo Segura basins. From these ruptures, we have selected maximum earthquake scenarios, and those associated with certain probabilities of exceeding a severe magnitude from the synthetic catalog. The estimation of maximum peak accelerations (PGA) by means of ground motion prediction equations include a possible site amplification that we have calculated from a detailed geotechnical classification of soils. According to the simulations, the modeled faults have the capacity to generate maximum earthquakes with magnitudes ranging M W 6.7–7.4. Densely populated urban areas located along the Guadalentin valley, such as Lorca, could be subject to site-dependent PGA values close to 0.6 g on the Alhama de Murcia fault trace. Similar ground motion would affect the coastline of SE Alicante province when evaluating the maximum simulated event in the Bajo Segura offshore fault. But already from magnitudes around M W ∼ 6, PGA estimations exceed critical values of 0.5 g at the south side of the Bajo Segura basin and the city of Murcia, highly dependent of ground-motion amplification induced by thick deposits of very soft and saturated soils. Our scenarios reflect that other factors such as fault geometry, kinematics and the capability observed in the simulations to generate multi-fault ruptures also affect the spatial distribution of maximum ground motion in this region. We expect that this evaluation could contribute as an improvement guideline for future strong motion prediction studies prior to the settlement of new urban infrastructures in the Eastern Betics. • Physics-based simulations for a long-term catalog of large complex seismic ruptures. • Deterministic analysis of ground motion scenarios at the Eastern Betics. • Geotechnical classification of soils to include site amplification in hazard analysis. • Big earthquakes and soft soils may rise seismic threat in populated zones of SE Spain. [ABSTRACT FROM AUTHOR]

Interferometric synthetic aperture radar (InSAR) is a remote sensing tool used for monitoring urban areas affected by geological hazards. Here we analysed the effectiveness of stabilization works on a slow-moving landslide in Arcos de La Frontera (Cádiz, Spain) using a persistent scatterer interferometric approach. The works consisted on jet grouting of cement-based injections and were applied locally to stabilize the most damaged neighbourhood. We processed a large stack of Sentinel-1 SAR satellite acquisitions covering the period January, 2016, to March, 2023, and obtained surface velocity and displacement trends measured along the line of sight (LOS) of the satellite on both ascending and descending orbits. The results show a clear deceleration of the landslide head after mid-2018, suggesting the local stabilization works were effective after that time. Prior to mid-2018, the maximum LOS velocity of the landslide head was 2.2 cm/year in ascending orbit and 1.3 cm/year in the descending orbit, decreasing to 0.43 cm/year and 0.23 cm/year, respectively. The InSAR results were compared to in-situ monitoring data and revealed that the extent of the stabilization has influenced a much larger area beyond the zone of the local interventions. Overall, InSAR has proved a powerful and versatile tool to be implemented in operational geotechnical monitoring. [ABSTRACT FROM AUTHOR]

Cement stabilization of metallurgical residues is a frequently implemented option to reduce the associated environmental risks and thus simplify residue disposal procedures. As chemical stabilization is the first and main purpose of the process, physical testing of these stabilized residues is usually kept simple with unconfined compressive strength, permeability, and durability as the most frequently employed control tests. These tests are, however, unable to deliver a true image of the potentially complex mechanical behavior after stabilization of some important residues. One example is treated sludge. Stabilizing agents and fine residues are usually mixed at high water contents, resulting in a very porous microstructure, with fragile bonds. Under loading, rapid destructuration and compaction is possible and this process may be prone to material instabilities. These phenomena are experimentally and theoretically illustrated herein. The experimental illustrations are brought from a microstructural study and undrained triaxial campaign on a stabilized jarosite. The theoretical explanations are obtained from an elasto-plastic model previously employed for soft rocks. [ABSTRACT FROM AUTHOR]

The fault gouge of the Alhama de Murcia fault (southeast Spain) shows a texture that resembles a mylonite, including a prominent foliation, S-C fabric, and isoclinal folds. It also embeds a large number of isolated pulverized quartz clasts (PQCs). Structural analysis indicates that the gouge fabric was mainly developed by slow frictional sliding along phyllosilicate- lined Riedel shear bands during continued shearing. In contrast, the PQCs show tensile fracture network features that are typically reported in seismically pulverized rocks found along seismogenic faults. This suggests that quartz-clast pulverization was due to a transient dilatational mechanism rather than shearing. We propose that the PQCs are the result of a rapid confined stress drop related to transient tensile stresses during coseismic ruptures that interrupt creep faulting along the gouge zone. The present study suggests that there is probably a large amount of evidence for paleoseismicity in fault rocks that is currently overlooked. [ABSTRACT FROM AUTHOR]

A complete failure analysis of a complex landslide located in Southern Spain (the Diezma landslide) has been undertaken using geotechnical, geophysical and geological data. The triggering factors were a high groundwater level and the reduction in the shear strength parameters of the high-plasticity clay. The 2010 reactivation of the landslide was related to the poor performance of the first line of deep drainage wells, although the second and third line of wells and the anchored pile barrier were effective in preventing the landslide reaching the A-92 motorway. Analysis indicates that further reactivation of the Diezma landslide could take place following a period of heavy rain if the drainage wells are not properly maintained, or if an earthquake of M 4.0-5.0 occurs within 25 km of the site. [ABSTRACT FROM AUTHOR]

Abstract: Complex landslides in clay-bearing sediments are investigated in two moderate-relief regions of Southeast Spain. Both regions, more than 100km apart show landslides affecting the same Flysch formation, which outcrops widely in the central and western Betic Cordillera along the contact between the External (South Iberian Domain) and Internal (Alborán Domain) zones. Intense rainfall episodes can be considered as the main triggering factor for slope failures in these two areas. We have chosen two landslides (Diezma and Riogordo landslides), one from each area of study, to investigate their morphological and geotechnical features in order to establish the relative importance of the different controlling factors. From a kinematic point of view, the two features studied in detail can be referred as to rotational failures, evolving downhill to slow earthflows. The movement was concentrated on several surfaces developed on a clay-rich layer mostly constituted by smectite. This clay mineral is of critical relevance to the mechanical behaviour of soils and Flysch-like formations, being very consistent at dry conditions, but rapidly losing its strength at wet conditions. Thus, softened smectite-rich clay layers with high water contents can approach the properties of a lubricant, which, in turn, can be critical for slope stability. In addition to their high plasticity, these clays have a high swelling potential, which can induce significant vertical overpressure, thus reducing even more the strength properties of the Flysch formation. In Southeast Spain, a region with a Mediterranean rainfall regime, slope stability can be seriously influenced by the presence of these smectite-rich clay layers in a formation of regional extent, as is the case of the Flysch formation. Therefore, this lithologically-controlled factor should be taken into account when evaluating landslide hazard in the Betic Cordillera. [Copyright &y& Elsevier]

In this work we present a review of the current state of knowledge of the active faults in El Salvador and its seismo-tectonic implications. An updated map of active fault traces is combined with the spatial analysis of shallow seismicity, focal mechanisms, recent geodetic GPS velocities, local strain estimations and morpho-tectonic features to provide a synoptic view of the active tectonics of the El Salvador. The major faults selected as potential seismic sources bound tectonic blocks or regions that include GPS sites with consistent relative velocity vectors. We propose several active tectonic domains along El Salvador controlled by three current deformation regimes: a crustal block in the forearc sliver dominated by rigid westward translation with the faster and more homogeneous GPS velocities; three zones dominated by E-W distributed extensional coaxial deformation; and two bands with a deformation compatible with transtensional regime. In the Western sector of the ESFZ, GPS velocities and local structure suggest that E-W extension concentrates along the NNW-SSE oriented Santa Ana volcanic axis and it could connect to the north with the extensional region of the Ipala Graben. This is consistent with to the eastward shift of the North America-Cocos-Caribbean triple junction and "the closing of the zipper" proposed in recent models that progressively slows down the strike-slip movement along the northern limit of the forearc sliver. In the central sector large GPS velocity gradient parallel to the volcanic arc may be associated to complex and discontinuous structure of the ESFZ driving slowdown of the westward movement of local tectonic blocks. The southeaster sector of the ESFZ is an incipient large pull-apart structure affecting a pre-existing extensional N-S oriented fabric that induces two tectonic subdomains, the eastern one undergo E-W coaxial extension and the western one characterized by transtensional strain regime. We propose a new structural segmentation of the ESFZ considering that this fault zone includes all those structures that accommodate the relative velocity between the forearc sliver and the Chortís block. The 38 active faults with surface traces that are mapped for more than 5 km long proposed in this work, with maximum potential magnitude Mw ranging from 5.98 to 7.94, will contribute to improve regional and local seismic sources databases and seismic hazard assessment. • Review of the current state of knowledge of the active faults in El Salvador. • Updated active faults map consistent with GPS velocities distribution. • Three current deformation regimes along the El Salvador fault zone. [ABSTRACT FROM AUTHOR]