The Har-Us-Nuur fault corresponds to one of the longest (>500 km) strike-slip fault in Mongolian Altai. Despite the fault clearly affects Quaternary deposits, no major instrumental or historical earthquake is associated to it and only a few morphotectonic and paleoseismological analyses have been carried out to date. In this paper, we describe a new surface rupture in the southern section of the Har-Us-Nuur fault along which we study in detail a 20 km long section of it. A morphotectonic analysis yielded a minimum slip rate of 0.32 ± 0.04 mm.yr¯¹, while paleosismological investigations suggest a mean recurrence interval of about 8.1 ± 3.4 kyr from the characterization of three surface rupturing events that occurred during the past 23 kyr. Combining this interval with a 5 - 6 m displacement estimated for the last seismic event, and assuming it corresponds to a characteristic slip and recurrence interval, yields a slip rate of 0.62 ± 0.27 mm.yr¯¹. These preliminary results suggest that the Har-Us-Nuur fault slip rate is inframillimetric and therefore lower than previous published estimates. They also suggest that the fault is able of producing major earthquakes (Mw ≥7.5) separated by very long period of quiescence.

On February 6, 2023, southern Türkiye was hit by two major earthquakes at 01:17 UTC (Mw 7.8, Pazarcık, Kahramanmaraş) and at 10:30 UTC (Mw 7.6, Elbistan, Kahramanmaraş) leading to severe damages at the complex junction of the Dead Sea Fault (DSF), the Cyprus arc and the East Anatolian fault zone (EAFZ). The ruptures propagated along several known strands of the southwestern termination of the EAFZ, the main Pazarcık and Karasu valley faults and the Çardac-Sürgü fault. The spatial extent of the impacted zone (300 x 300 km) supports the use of satellite images to map ruptures and damages and measure the co-seismic displacement over the whole region. Among the different satellite constellation available nowadays, Sentinel-2 presents the advantages of offering high-resolution images (10 m), global coverage with frequent revisit time and open access policy to the images. We here present the high-resolution mapping of the entire coseismic surface ruptures derived from image correlation of optical Sentinel-2 satellite acquisitions. We further estimated the rupture width, the total and on-fault offset, and of the diffuse deformation obtained a few days after the two mainshocks along the two main ruptures at 50 m resolution along the rupture. The mapping and the estimation of the offset are validated with the location of the rupture and the offset measurements collected on the ground. We found that the ruptures extend over lengths of 310 km and 140 km, with maximum offsets reaching 7.5±0.8 m and 8.7±0.8 m near the epicenters, for the Mw 7.8 and Mw 7.6 mainshocks, respectively. We propose a segmentation of the two ruptures based on these observations, and further discuss the location of potential supershear rupture. The use of optical image correlation complemented by field investigations along earthquake faults provides new insights into seismic hazard assessment.

Landform mapping is the initial step of many geomorphological analyses (e.g. assessment of natural hazards and natural resources) and requires vast resources to be applied to wide areas at high-resolution. Among geomorphological objects, we focus on glacial moraine mapping, since it is a task relevant to many fields (e.g. paleoclimate and glacial geomorphology). Here we proposed to exploit the potential of Deep Learning-based approaches to map moraine landforms by exploiting multi-source remote sensing imagery. To this end, we propose the first Deep Learning model to map glacial moraines, namely MorNet. As multi-source remote sensing information, we combine together three different sources: Topographic (Pleiades-derived DSM), Multispectral (Sentinel-2), and SAR (Sentinel-1) data. To cope with such heterogeneous information, the proposed model has a dedicated branch for each input source and, a late fusion mechanism is leveraged to combine them with the aim to provide the final mapping. The performance of the MorNet model is evaluated on several glacier valleys in China in the Himalayan range. This area contains minimally eroded moraines, so they are well-defined and of varied morphology. The behavior of the proposed method is compared to models using individual mono-source models in order to highlight the benefit to simultaneously leverage multi-source information. The use of multi-source data allows MorNet to exploit the complementarity of the three input sources and improve its performance from an f1-score of about 41.6 using a single source to 52.8 using three sources. MorNet provides a first-order moraine map through its ability to identify well-defined moraines. Consequently, MorNet can identify areas likely to contain moraines and intends to be used as a tool by experts to facilitate and support large-scale mapping.

On February 6, 2023, southern Türkiye was hit by two major earthquakes at 01:17 UTC (Mw 7.8, Pazarcık, Kahramanmaraş) and at 10:30 UTC (Mw 7.6, Elbistan, Kahramanmaraş) leading to severe damages at the complex junction of the Dead Sea Fault (DSF), the Cyprus arc and the East Anatolian fault zone (EAFZ). The ruptures propagated along several known strands of the southwestern termination of the EAFZ, the main Pazarcık and Karasu valley faults and the Çardac-Sürgü fault. The spatial extent of the impacted zone (300 x 300 km) supports the use of satellite images to map ruptures and damages and measure the co-seismic displacement over the whole region. Among the different satellite constellation available nowadays, Sentinel-2 presents the advantages of offering high-resolution images (10 m), global coverage with frequent revisit time and open access policy to the images. We here present the high-resolution mapping of the entire coseismic surface ruptures derived from image correlation of optical Sentinel-2 satellite acquisitions. We further estimated the rupture width, the total and on-fault offset, and of the diffuse deformation obtained a few days after the two mainshocks along the two main ruptures at 50 m resolution along the rupture. The mapping and the estimation of the offset are validated with the location of the rupture and the offset measurements collected on the ground. We found that the ruptures extend over lengths of 310 km and 140 km, with maximum offsets reaching 7.5±0.8 m and 8.7±0.8 m near the epicenters, for the Mw 7.8 and Mw 7.6 mainshocks, respectively. We propose a segmentation of the two ruptures based on these observations, and further discuss the location of potential supershear rupture. The use of optical image correlation complemented by field investigations along earthquake faults provides new insights into seismic hazard assessment.

On February 6, 2023, southern Türkiye was struck by two large earthquakes at 01:17 UTC (Mw=7.8, Pazarcık, Kahramanmaraş) and 10:30 UTC (Mw = 7.6, Elbistan, Kahramanmaraş), causing severe damage at the complex junction of the Dead Sea Fault (DSF), the Cyprus Arc and the East Anatolian Fault Zone (EAFZ). The ruptures propagated along several known strands of the southwestern termination of the EAFZ, the main Pazarcık and Karasu valley faults, and the Çardak-Sürgü fault. Here we present the high-resolution mapping of the entire coseismic surface rupture and an estimate of the rupture width, total and on-fault offset, and diffuse deformation obtained a few days to three months after the two mainshocks. The mapping is derived from image correlation of Sentinel-2 optical satellite imagery and validated with offset measurements collected on the ground. We find that the ruptures extend over lengths of 310 km and 140 km for the Mw 7.8 and Mw 7.6 mainshocks, respectively. The maximum offsets reach 7.5 ± 0.8 m and 8.7 ± 0.8 m near the epicenters of the Mw 7.8 and Mw 7.6 events, respectively. We propose a segmentation of the two ruptures based on these observations, and further discuss the location of the potential supershear rupture. The use of optical image correlation, complemented by field investigations along earthquake faults, provides new insights into seismic hazard assessment.

AbstractDeformed alluvial terraces are ubiquitous markers of a fault’s recent activity and may help assess its slip rate and associated seismic hazard. They are often considered as a nearly flat surface translated and rotated along a planar or listric fault. The present study challenges these assumptions by revealing uneven terrace treads and verticalization of the Topographic Frontal Thrust (TFT) in south-central Bhutan. We model this finding as combined variability in both the aggradation and geometry of the TFT. We estimate a Holocene slip rate of 19.6 ± 4.1 mm.yr−1, which confirms that the TFT accommodates most of the shortening across the range. Contrary to previous studies, we find an excess of slip over the last few centuries, which implies a lower seismic hazard. These results highlight the importance of considering the non-planar component in terrace shape, shallow abrupt changes in fault geometry, and aggradation in future morphotectonic studies worldwide.

We present a 1:200,000 scale map of the Ar-Hotol surface rupture along the Khovd fault (Mongolian Altay), presumed to be the expression of the 1761 CE Mw similar to 7.8 Great Mongol earthquake. The detailed mapping combines airborne and terrestrial imaging and topographic techniques (Sentinel-2, Pleiades, TanDEM-X, UAV and TLS) to quantify right-lateral and vertical offsets ranging from similar to 1 m to similar to 4 km over a length of 238 km. The smaller offsets document the deformation associated with the last surface-rupturing earthquake that affects several Bronze to Iron Age burial mounds. Their analysis yields a robust segmentation model comprising 6 segments of 20 to 51 km in length, a maximum co-seismic slip value of 4.8 m +/- 0.5 m located near the center of the rupture. Our observations precise the varying kinematics along strike, bring new evidence of repeated faulting and confirm a Mw of 7.8 +/- 0.3.

The Himalayan range is affected by very strong, devastating earthquakes that have been mentioned in historical chronicles on numerous occasions since the medieval period. Strong devastating earthquakes affect the entire Himalayan range. These earthquakes result from plate tectonics, and more specifically from the India–Asia convergence. On the morning of October 8, 2005, a very strong earthquake devastated Pakistani Kashmir and in particular the city of Muzaffarabad. This event, of magnitude 7.6, left 80,000 people dead. It is the first of the large Himalayan earthquakes studied jointly by modern techniques of seismology and satellite imagery. Extensive field surveys along the meso-seismal traces of the strongest instrumental and historical earthquakes helped discover remnants of their surface ruptures. Since then, more than 27 paleoseismological trench sites have been excavated along the Himalayan arc.

The Ganos fault that ruptured on 9 August 1912 (Mw: 7.4) is the westernmost inland segment of the North Anatolian fault (NAF). Here, the Ganos fault is bounded at its two tips with offshore faults segments, in the Sea of Marmara to the east and the Gulf of Saros to the west in the North Aegean Trough. Therefore, the paleoseismology of the 45-km-long inland fault is of importance to the seismic hazard analysis related to offshore active faults and in particular for the seismic gap in the Marmara Region. Earlier studies have established an earthquake chronology for the western and eastern inland tips of the Ganos fault. Here, we extend the paleoseismic studies toward the central segment. Three trenches at Yörgüç have revealed evidence for two faulting events, possibly post-1669 CE ±30 years, which can be correlated to the 1659 or 1766, and the 1912 historical earthquakes. At Yeniköy, we determined an offset of 46 ± 1 m and 47 ± 1 m on a stream channel and a ridge-crest, respectively. In two trenches we determined two faulting events for the last 1000 years and seven events for the last 3500 years. In trench T5, the base of the displaced stream channel provides a calibrated date of 829?591 BCE. Using the 46 ± 1 m right-lateral displacement, we calculate a slip rate of 16.9 ± 0.7 mm/year for the last 2732 ± 119 years. A combined analysis with earlier paleoseismic studies on the Ganos fault suggests that the historical earthquakes of 1912, 1766b or 1659, 1354 or 1343a, and 1063 ruptured the entire inland fault section. In such a case, the recurrence interval for this section of the NAF corresponds to 283 ± 81 years. Combining earlier estimations, we suggest an average slip rate of 17.1 ± 0.9 mm/year for the last 2700 years and observe a characteristic slip behavior of 4.5 to 5 m per event for this section of the North Anatolian plate boundary fault.

<p>Long-term fault escarpments are built by the accumulation of individual earthquakes producing incremental surface displacements on the fault releasing crustal tectonic loading. Cumulative escarpment studies have revealed a spatial slip variability along active faults as well as a temporal variability with the alternation of phases of intense seismic activity over a short period of time followed by long periods of quiescence. Understanding this spatial and temporal slip variability on individual faults and over a complex fault system provide a better knowledge of co-seismic rupture extents, essential for estimating past earthquakes magnitude and for seismic hazard assessment.</p> <p>Up to now, most studies have focused on a timeframe over few seismic cycles, making it difficult to apprehend the rupture barriers persistence and cumulative slip distribution.  Here, we aim at quantifying the slip variability over several timescales ranging from a few months to a few million years on the same fault.</p> <p>Our study focusses on the ~50 km-long Liri fault, SW of the Fucino basin. The fault is located at the contact between Cretaceous limestone and patches of Quaternary deposits locally convering Mio-Pliocene flysch sediments. Detailed mapping of the fault trace on high-resolution Digital Elevation Model (DEM) from UAV-acquired images, Pleiades images and Lidar together with field observations revealed changes in the morphological expression of the fault north and south of an important wind gap located at Capistrello. To the north, the faut trace is ~16 km-long located on the eastern side of ~2km-wide limestone ridge, reaching ~1300m asl elevation. Two bends in the fault trace, made of ~5km long segments, can be observed with the fault strike varying between N115° and N140°. In this northern section, the fault scarp appears subtle and we did not observe Quaternary deposits on the hanging wall. In the 30 km-long section, south of Capistrello, the cumulative scarp composed of numerous splays is evidenced by a sharp trace, offsetting several morphological surfaces and associated Quaternary sediment packages. Three major bends are observed in this section of the fault, separating 10 to 30 km-long segments striking between N110° and N160°. An alluvial surface offset by ~14 m of cumulative displacement was dated at ~35kyr using <sup>36</sup>Cl cosmogenic exposure dating suggesting a minimum slip rate of 0.4 mm/yr.  Other morphological markers that have accumulated displacement between ~10 and 70 m-high have also been sampled for <sup>36</sup>Cl cosmogenic exposure dating. Moreover, we excavated two small trenches at the base of the fault scarp within the Quaternary deposits affected by the fault revealing 3 rupture-surfacing earthquakes over the last 2500 yr, the last one occurring after 1226 CE. </p> <p>We will present those results and will discuss how the displacement varies along the fault both in time and space.</p>

The Ar-Hötöl surface rupture along the Khovd fault (Mongolian Altay) Battogtokh Davaasambuu1,2, Matthieu Ferry1,*, Jean-Francois Ritz1 and Ulziibat Munkhuu2 * Géosciences Montpellier, University of Montpellier, CNRS, France * Institute of Astronomy and Geophysics, Mongolian Academy of Sciences, Mongolia Abstract The Khovd fault is one of the major active faults of the Altay but has been little studied. Detailed mapping based on satellite imagery shows that the Khovd structure exceeds 550 km in length and displays different types of complex rupture segmentation, fresh and mature surface ruptures and a number of co-seismic and cumulative offsets along its entire length. We present a 1:200,000 scale map of the Ar-Hötöl surface rupture along the Khovd Fault in the Mongolian Altay, presumed to be the surface expression of a Mw ~ 7.8 earthquake that was felt regionally in 1761 CE. The detailed mapping is based on a multi-scale approach combining a range of airborne and terrestrial imaging and topographic techniques: Sentinel-2, Pleiades, TanDEM-X, UAV, and terrestrial laser scanning. This effort led to the detailed quantification of right-lateral and vertical offsets ranging from ~ 1 m to ~ 4 km over a continuous rupture length of 238 km. The distribution of the smaller offset class documents the surface deformation associated with the last surface-rupturing earthquake. Its analysis yields a robust segmentation model comprising 6 segments 18 to 55 km in length, a maximum co-seismic slip value of 4.5 m ± 0.5 m located near the center of the rupture. Our detailed remote sensing and field observations precise the varying kinematics along strike, bring new evidence of repeated faulting and confirm a moment magnitude of 7.8 ± 0.3. The aim of the present research work is to reveal the main sources of potential destructive earthquakes by identifying the location of past large earthquakes along the fault and estimate their magnitude and recurrence period. Our results would contribute to improve seismic hazard estimation for population of the Altay Mountains. Keywords: active fault, surface rupture, Altay Range

. On November 11, 2019, a M w 4.9 earthquake hit the region close to Montelimar (lower Rhône Valley, France), on the eastern margin of the Massif Central close to the external part of the Alps. Occuring in a moderate seismicity area, this earthquake is remarkable for its very shallow focal depth (between 1 and 3 km), its magnitude, and the moderate to large damages it produced in several villages. InSAR interferograms indicated a shallow rupture about 4 km long reaching the surface and the reactivation of the ancient NE–SW La Rouvière normal fault in reverse faulting in agreement with the present-day E–W compressional tectonics. The peculiarity of this earthquake together with a poor coverage of the epicentral region by permanent seismological and geodetic stations triggered the mobilisation of the French post-seismic unit and the broad French scientific community from various institutions, with the deployment of geophysical instruments (seismological and geodesic stations), geological field surveys, and field evaluation of the intensity of the earthquake. Within 7 days after the mainshock, 47 seismological stations were deployed in the epicentral area to improve the Le Teil aftershocks locations relative to the French permanent seismological network (RESIF), monitorthetemporalandspatialevolutionofmicroearthquakesclosetothefaultplaneandtemporal evolutionoftheseismicresponseof3damagedhistoricalbuildings,andtostudysuspectedsitee ff ects and their influence in the distribution of seismic damage. This seismological dataset, completed by data owned by di ff erent institutions, was integrated in a homogeneous archive and distributed through FDSN web services by the RESIF data center. This dataset, together with observations of surface rupture evidences, geologic, geodetic and satellite data, will help to unravel the causes and rupture mechanism of this earthquake, and contribute to account in seismic hazard assessment for earthquakesalongthemajorregionalCévennefaultsysteminacontextofpresent-daycompressional tectonics.

The 2019-11-1, Mw4.9 Le Teil earthquake occurred within the NE termination of the Cévennes faults system (CFS) in southern France, along the La Rouvière fault (LRF), an Oligocene normal fault which was not known to be potentially active. This shallow moderate magnitude reversefaulting event produced a 5 km-long surface rupture and strong ground shaking. No evidence of previous quaternary activity was observed in the morphology, raising the question whether the fault had been reactivated for the first time since the Oligocene or had broken the surface in the past without being detected in the morphology. To address this issue, we carried out paleoseismological investigations to analyze and characterize evidences of paleo-ruptures in Quaternary deposits. We discovered that at least one event prior 2019, occurred between 13.5 and 3.3 ka within the central part of the fault segment that broke in 2019, and that a possible earlier surfacerupturing event occurred within the northern part of this segment during the 16th century. Further investigations coupling sub-surface geophysical investigations and trenching are now carried out within the southern and northern segments of the LRF as well as along the other fault segments of the CFS.

Offset streams are well recorders of the long-term and short-term deformation along strike-slip faults. Two independent processes act during the formation of offset streams: (1) climatic processes that support stream formation; (2) successive fault displacement across the stream channel. Field investigations are conducted along the westernmost inland segment of the North Anatolian fault; the Ganos fault; 48 right-lateral stream offsets are documented ranging 8 to 575 m. The stream offsets show five distinct groups of comparable magnitude that can be explained as episodes of new stream incisions due to high precipitation periods. Paleoclimatic studies in the region reveal the timing of these periods. Using a Black Sea sea-level curve for the last 20 ka, five subsequent sea-level rise periods are determined at 4, 10.2, 12.5, 14.5, and 17.5 ka. They can be considered as climatic periods favorable for stream incisions in the Ganos area. Linking the five offset groups with precipitation periods provides an average 17.9 mm/year slip rate for the last 20.000 years and a variability of 17.7 mm/year, 17.7 mm/year, 17.9 mm/year, and 18.9 mm/year for the last 10.2 ka, 12.5 ka, 14.5 ka, and 17.5 ka, respectively. These results are comparable with values for the eastern parts of the NAF, ranging from 15 to 25 mm/year.

We present first constraints from tectonic geomorphology and paleoseismology along the newly discovered Sharkhai fault near the capital city of Mongolia. Detailed observations from high-resolution Pleiades satellite images and field investigations allowed us to map the fault in detail, describe its geometry and segmentation, characterize its kinematics, and document its recent activity and seismic behavior (cumulative displacements and paleoseismicity). The Sharkhai fault displays a surface length of ∼ 40 km with a slightly arcuate geometry, and a strike ranging from N42 to N72∘. It affects numerous drainages that show left-lateral cumulative displacements reaching 94 m. Paleoseismic investigations document faulting and depositional/erosional events for the last ∼ 3000 years and reveal that the most recent event occurred between 775 and 1778 CE and the penultimate earthquake occurred between 1605 and 835 BCE. The resulting time interval of 2496 ± 887 years is the first constraint for the Sharkhai fault for large earthquakes. On the basis of our mapping of the surface rupture and the resulting segmentation analysis, we propose two possible scenarios for large earthquakes with likely magnitudes of 6.7 ± 0.2 or 7.1 ± 0.7. Furthermore, we apply scaling laws to infer coseismic slip values and derive preliminary estimates of long-term slip rates. Finally, these data help build a comprehensive model of active faults in that region and should be considered in the seismic hazard assessment for the city of Ulaanbaatar.

The 11-11-2019 Le Teil earthquake (Mw4.9), located in the Rhône river valley occurred along the La Rouvière fault (LRF) within the NE termination of the Cévennes faults system (CFS). This very shallow moderate magnitude and reverse-faulting event inverted an Oligocene normal fault which was not assessed to be potentially active, causing surface rupture and strong ground shaking. Its morphology shows no evidence of cumulative reverse faulting during the Quaternary. All of this information raises the question of whether the fault was reactivated for the first time since the Oligocene during the Teil earthquake, or if it had broken the surface before, during the Quaternary period, but could not be detected. In addition, it poses the question of the potential reactivation of other faults of the CFS and other faults in metropolitan France as well. To tackle those issues, we launched paleoseismic investigations along the LRF to analyze and characterize evidences of paleo-ruptures in Quaternary deposits. Twelve trenches were dug along the section that broke in 2019. The trenches were dug in aeolian deposits and slope colluvium lying against the ancient LRF normal fault mirror carved in the Barremian limestones. Five trenches yielded favorable Quaternary deposits to document deformation suggesting that one paleo-event, maybe more, occurred with kinematic characteristics (sense of movement, amount of displacement) similar to the 2019 event. The radiocarbon dating of the deformed units (“bulks” collected from the colluvium clayey-silty matrix) suggests, in particular, that at least one event occurred in the past 13 Ka (i.e. penultimate event prior to the Teil earthquake) . The fact that these events are not preserved in the morphology is explained by the small amount of displacement and a long return period, consistent with the low strain rate measured by GPS in this region (~10-9 yrs-1). Our study shows that it is therefore fundamental to carry out more detailed paleoseismological investigations in metropolitan France, especially along ancient faults favorably oriented with respect to the present stress field. Those are already planned in the next coming months along other segments of the CFS.

Mainland France is part of a plate interior with a strong structural heritage, undergoing a low rate of deformation, where destructive earthquakes can nevertheless occur. In this paper, we emphasize that the knowledge of active faults is still largely fragmentary, and that significant efforts are needed to generate robust data, in particular on the numerous faults, that still lack any study. This is the aim of the “Failles ACTives France” (FACT) axis launched in the framework of the Transverse Seismicity Action (ATS) of the Resif-Epos consortium. We present some recent investigations carried out along suspected active faults in mountainous areas, their forelands and remote lowlands, which implement new approaches and new tools, and allow characterizing their Quaternary activity.

The 11-11-2019 Le Teil earthquake (Mw4.9), located in the Rhône river valley occurred along the La Rouvière fault (LRF) within the NE termination of the Cévennes faults system (CFS). This very shallow moderate magnitude and reverse-faulting event inverted an Oligocene normal fault which was not assessed to be potentially active, causing surface rupture and strong ground shaking. Its morphology shows no evidence of cumulative reverse faulting during the Quaternary. All of this information raises the question of whether the fault was reactivated for the first time since the Oligocene during the Teil earthquake, or if it had broken the surface before, during the Quaternary period, but could not be detected. In addition, it poses the question of the potential reactivation of other faults of the CFS and other faults in metropolitan France as well. To tackle those issues, we launched paleoseismic investigations along the LRF to analyze and characterize evidences of paleo-ruptures in Quaternary deposits. Twelve trenches were dug along the section that broke in 2019. The trenches were dug in aeolian deposits and slope colluvium lying against the ancient LRF normal fault mirror carved in the Barremian limestones. Five trenches yielded favorable Quaternary deposits to document deformation suggesting that one paleo-event, maybe more, occurred with kinematic characteristics (sense of movement, amount of displacement) similar to the 2019 event. The radiocarbon dating of the deformed units (“bulks” collected from the colluvium clayey-silty matrix) suggests, in particular, that at least one event occurred in the past 13 Ka (i.e. penultimate event prior to the Teil earthquake) . The fact that these events are not preserved in the morphology is explained by the small amount of displacement and a long return period, consistent with the low strain rate measured by GPS in this region (~10-9 yrs-1). Our study shows that it is therefore fundamental to carry out more detailed paleoseismological investigations in metropolitan France, especially along ancient faults favorably oriented with respect to the present stress field. Those are already planned in the next coming months along other segments of the CFS.