TREAD is a new project funded by the European Commission in the framework of Marie Sklodowska-Curie actions, Horizon Europe Doctoral Networks.

The aim of TREAD is to train a new generation of researchers to tackle the challenges of earthquake forecasting in complex tectonic settings using integrated observations and physics. The TREAD objectives are: (i) to develop a novel integrative approach to seismic hazard analysis in Europe and the Mediterranean from small-scale laboratory experiments to large-scale observations. (ii) to establish physics-based earthquake modelling bridging time scales from millions of years to fractions of a second in complex tectonic settings. (iii) to improve the link between earthquake geology, computational modelling and hazard and risk assessment with a focus on the needs of governments, industry and scientific stakeholders.

How to cite: Pace, B., Benedetti, L., Van Dinther, Y., Pagani, M., Marsan, D., Gabriel, A., Ortuno, M., Di Toro, G., and Meier, M.-A. and the TREAD working group: TREAD daTa and pRocesses in sEismic hAzarD: a MSCA-Doctoral Networks project 2023-2027, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3842, https://doi.org/10.5194/egusphere-egu23-3842, 2023.

In the Alboran Sea, oblique convergence between the African and Eurasian plates led to the establishment of the Al Idrissi sinistral strike-slip fault system, initiating a new plate boundary, 1 Ma ago. Several moderate magnitude earthquakes (Mw > 6) have been recorded on different segments of this fault system. The objective of this study is to analyse the dynamics of this plate boundary by studying the tectonic activity and physical properties of the sedimentary series along a key transect of the fault system. To do so, we used a panel of geological, geophysical and geotechnical tools, some of which were acquired during the ALBACORE oceanographic campaign (R/V Pourquoi Pas? 2021).

The data analysed are derived from (i) sediment cores of the ALBACORE oceanographic cruise (with multi-sensor core logger - MSCL), (ii) heat flux measurements, (iii) penetration tests with the Ifremer Penfeld piezocone (CPTU) as well as (iv) multibeam bathymetry data and (v) seismic reflection/depth data. These data were acquired along a transect of the Bokkoya fault system, south of the Al Idrissi fault system. The length of the sedimentary series investigated allows the dating of major sedimentary events that occurred during the late Pleistocene and Holocene. Along this segment, isotope analysis of the carbonate biogenic components provided a 𝛿18O evolution curve that was converted into time series. Thus, a chronostratigraphic framework up to 80 ky could be constrained as well as variations in sedimentation rate between compartments on either side of the fault. The analysis of physical properties using heat flow, CPTU and MSCL data allows a detailed lithological and geophysical stratigraphy to be established along the transect and highlights the variability of geological, geotechnical and geophysical signatures on either side of the fault system.  This work is part of the ANR ALBANEO project, which aims to understand the dynamics of this new plate boundary and, in the longer term, to assess the hazards in this area of the western Mediterranean Sea.

How to cite: Vidil, L., d'Acremont, E., Leroy, S., Lafuerza, S., Emmanuel, L., and Rabaute, A. and the ALBACORE and ALBANEO teams: Geological, geophysical and geotechnical highlights of the southern part of the Al Idrissi strike-slip fault system from the Alboran sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6872, https://doi.org/10.5194/egusphere-egu23-6872, 2023.

As part of the recently initiated research project, we are in the process of studying in detail the geodynamic behavior of the Carboneras fault (CF) in the SE Betics in Spain. Specifically, we plan to quantify the geodetic and geologic slip rates for the on-land section of the fault, as well as getting some insight on the state of locking of the fault. As a result of our previous GPS observations, we have been able to illustrate the continuing tectonic activity of the Carboneras fault, expressed mainly as a left-lateral strike slip motion of 1.3±0.2 mm/yr, with a less significant compression of 0.4±0.2 mm/yr (Echeverria et al., 2015). To reveal how the deformation is partitioned between different structures, in the last years 2 new continuous GPS points were established along the fault-perpendicular profile. In addition, we have conducted several surveys of the nearby CuaTeNeo and IGN Regente points and established and measured several new geodetic points in the vicinity of the Carboneras fault. The updated horizontal geodetic slip rates for the CF are 1.1±0.2 and 0.4±0.3 mm/yr in fault parallel and perpendicular directions, respectively. These estimates are somewhat smaller than previously published results, although considering the uncertainties, are statistically equivalent.

The above-mentioned geodetic, short-term, slip rates deduced from GNSS observations, are in good agreement with the estimates of geologic slip rates based on paleoseismic and geomorphologic studies, which indicate a minimum strike-slip rate of 1.3 mm/yr and dip-slip rate of 0.05 mm/yr since 110.3 ka (Moreno et al. 2015). In the coming years we plan to conduct further geodetic surveys and paleoseismic trenching surveys. These new data, should significantly improve the reliability of the existent deformation data and therefore, contribute to better understanding of the seismic hazard posed by the Carboneras fault in the SE Betics.

Project NSOURCES (PID2020-119772RB-I00) financed by MCIN/AEI/10.13039/501100011033

How to cite: Khazaradze, G., Gómez-Novell, O., Ortuño, M., Masana, E., and Pallàs, R.: Geodetic vs. geologic measures of fault slip rates of the Carboneras fault in the Betics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13443, https://doi.org/10.5194/egusphere-egu23-13443, 2023.

Fault displacement can be a source of hazard for critical infrastructures located in the nearby of a capable fault.  This issue is usually addressed with zonation and avoidance strategies, but sometime the facilities have not this option. An alternative approach to assess likelihood of exceeding a certain level of displacement for pre-existing infrastructures is the Probabilistic Fault Displacement Hazard Analysis. Different empirical approaches have been proposed since the early 2000s to assess the probability of occurrence and the probability of exceedance of certain values of displacement, for both Primary and Distributed faulting, starting from the fault parameters.            
We propose the methodological approach used to gain the needed parameters and the results of the PFDHA applied to the Anghiari Fault, a poorly constrained NE-dipping segmented normal fault located in the Upper Tiber Valley (Italy) and belonging to the well-known Altotiberina low-angle normal fault system.

In order to constrain the fault geometry and to select sites suitable for paleoseismologic trenching we performed geological survey, morphotectonic analysis and geophysical investigations. To assess the capability of the fault and its rate of activity we carried out a paleoseimic campaign, investigating several segments of the Anghiari fault. To obtain a multiscale evaluation of the fault slip rate, we collected samples to date paleosurfaces displaced by the fault with the cosmogenic nuclides methodology.           
At the end we performed the PFDHA obtaining curves and maps of hazard for both primary and distributed faulting, managing the uncertainties through various rupture scenario involving different fault segment.

How to cite: testa, A., Boncio, P., Baize, S., Mirabella, F., Pucci, S., Pauselli, C., Ercoli, M., Pace, B., and Benedetti, L.: Earthquake geology for fault displacement hazard analysis of normal faults, a case study from the Upper Tiber Valley (Northern Apennines, Italy)., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-805, https://doi.org/10.5194/egusphere-egu23-805, 2023.

A sedimentological, geochronological, and geodynamic investigation of detailed micro- and meso-scale soft-sediment deformation structures (SSDS) within internally deformed layers on Gnitz Peninsula, Usedom Island, Germany, was performed in the last years. Five layers with SSDS were described of which four were possibly caused by glacial isostatic adjustment (GIA)-triggered earthquakes mirrored in liquefaction and reliquefaction phenomena (Pisarska-Jamroży et al., 2022). Hence, in line with earlier investigations and suggestions by Hoffmann and Reicherter (2012), the SSDS generation is related to oscillation of the Scandinavian Ice Sheet whose loading cycle caused stress changes likely releasing local earthquakes along pre-existing faults.

Optically stimulated luminescence dating indicates a most probable time span of corresponding earthquake occurrence between 23.2 and 14.6 ka (including uncertainty). For the first time, glacially induced Coulomb failure stress changes were modelled for this area with a set of commonly accepted GIA models. They strongly support the interpretation of SSDS trapped in layers as seismites during that time. Using reliable fault parameters of faults in near vicinity of Gnitz Peninsula and suggested stress regimes and directions for northern Germany, the modelling can help indicate the most probable reactivated pre-Quaternary fault(s). If they can be confirmed after detailed palaeoseismological, geomorphological, geophysical, and structural investigations as so-called glacially induced fault(s), this would add another puzzle piece to a geodynamic scenario of glacially triggered faulting having affected an area from northern central Europe to northern Fennoscandia in the Late Pleistocene and Early Holocene.

Our presentation will focus on the geodynamic setting of NE Germany, how it was changed during the last glaciation and how potentially reactivated faults can be determined.

References

Hoffmann, G., Reicherter, K., 2012. Soft-sediment deformation of late Pleistocene sediments along the southwestern coast of the Baltic Sea (NE Germany). Int. J. Earth Sci. 101, 351-363, doi:10.1007/s00531-010-0633-z.

Pisarska-Jamroży, M., Belzyt, S., Börner, A., Hoffmann, G., Kenzler, M., Rother, H., Steffen, R., Steffen, H., 2022. Late Pleistocene earthquakes imprinted on glaciolacustrine sediments at Gnitz Peninsula (Usedom Island, NE Germany). Quat. Sci. Rev. 296C, 107807, doi:10.1016/j.quascirev.2022.107807.

How to cite: Steffen, H., Pisarska-Jamrozy, M., Belzyt, S., Börner, A., Hoffmann, G., Kenzler, M., Rother, H., and Steffen, R.: Which fault was it? - Late Pleistocene, glacially triggered earthquakes in NE Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9718, https://doi.org/10.5194/egusphere-egu23-9718, 2023.

The eastern Rhine Graben Boundary fault (eastern RGBF) constitutes the eastern margin of the Upper Rhine Graben (URG), the most seismically active area in the plate interiors of Europe. Our recent paleoseismic studies have revealed Late Pleistocene-Holocene surface-rupturing paleoearthquakes with magnitudes M 6–6.5 and cumulative surface displacements in the order of 1–1.2 m vertically and 4–6 m horizontally. Based on the empirical relationships of Wells and Coppersmith, these parameters suggest that the plausible rupture scenarios of those paleoearthquakes are linked to shorter fault segments within the 300 km long eastern RGBF rather than an entire rupture of the fault. Up to date, segmentation on faults of the URG has yet to be evaluated. We aim to define fault segments within the eastern RGBF and their relative tectonic activity to understand how deformation is distributed along the marginal faults and within the graben. To achieve this, we integrate seismicity data, morphotectonic observations (from SRTM, TanDEM-X and LiDAR-based DEMs), geology (Plio-Pleistocene sediment thickness), and interpretation of commercial seismic lines.

We define up to seven segments of varying lengths based on geometric and structural fault trace discontinuities (bend, gaps, and changes in strike and dip) and the occurrence and degradation state of tectonic landforms (triangular facets, beheaded channels, hanging valleys and offset alluvial fans), which we also take into account to define the relative level of tectonic activity at each segment. The most active segments are the South-Kraichgau and Freiburg segments, with potential magnitudes of M 7–7.5 (including the historical M 6.7 Basel eq of 1356). The northern area, comprising the Frankfurt-Darmstadt and Odenwald segments, constitute presently a seismic gap with quiescence in historical and instrumental seismicity but with tectonic expression in the landscape and thickest Late Tertiary-Pleistocene deposits, suggesting a potential hazard. Our results provide a basis to propose plausible rupture scenarios for the eastern RGBF for future PSHA studies.

How to cite: Pena-Castellnou, S., Baize, S., Hürtgen, J., and Reicherter, K.: A segment model for surface rupture scenarios in the eastern Rhine Graben Boundary fault (Upper Rhine Graben, Germany), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14783, https://doi.org/10.5194/egusphere-egu23-14783, 2023.

Namibia is situated within a stable continental region (SCR), far away from plate boundary zones, and is therefore not expected to be at risk of significant earthquakes; the largest events in the instrumental record have a moment magnitude of 5.5.  Despite this, a paleoseismic fault scarp on the Hebron Fault has been interpreted as indicating much larger events have occurred in the past.  In this study, we demonstrate that a relatively small area of SW Namibia contains four more major neotectonic fault scarps.  These 16-80 km long structures have vertical separations between 0.7-10.2 m and could produce earthquakes of Mw 6.4 or greater.  Some of these scarps are interpreted to have formed through repeated failure of the same segment and they highlight the potential for further seismicity that far exceeds the maximum observed magnitude in the national catalogue. We identify strong structural controls on the location and orientation of these fault ruptures which reactivate N-S and NW-SE trending zones of crustal weakness.  These structures may be driven by E-W extension associated with the distribution of gravitational energy caused by the anomalously high elevation of the Namibian Escarpment.  If this explanation of the driving stresses is correct, these and similarly oriented faults represent a previously unrecognised source of continuing seismic hazard.  The discovery of these major fault scarps suggests that fault studies should be incorporated into seismic hazard analyses of stable Southern Africa as has been done in Australia and other SCR regions. Their apparent spatial clustering also merits further study.  At this point it is not clear if this clustering indicates a region of elevated strain rate (relative the surrounding SCR) or alternatively, an area of exceptional preservation due to a semi-arid climate and extensive calcrete-cemented surficial deposits.

How to cite: Sloan, R. A., Muir, R., Whitehead, B., New, T., Stevens, V., Macey, P., Groenewald, C., Salomon, G., Kahle, B., and Hollingsworth, J.: Exceptionally preserved neotectonic fault scarps in SW Namibia record large-magnitude structurally-controlled SCR paleoseismicity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11719, https://doi.org/10.5194/egusphere-egu23-11719, 2023.

Joint interpretation of multidisciplinary geophysical data is the best way to reduce ambiguity in subsurface exploration. The combination of seismic velocity and electrical
resistivity has proven to be an excellent geological characterization strategy, however, the integration of these geophysical parameters is a complex process. In this work, we use unsupervised clustering to jointly interpret three geophysical datasets (P wave velocity, S wave velocity, and electrical resistivity). The target is a cross-section across the Alhama de Murcia Fault (FAM), which is one of the main active faults in the Iberian Peninsula. In our approach, we first join the three datasets into a common multiparametric grid. Then, in order to find data clusters that can be correlated with known lithologies in the area, we investigated the performance of three unsupervised machine learning algorithms: one hierarchical, one centroid-based, and one model-based. The latter proved to be the most efficient for clustering our highly mixed data and providing geological meaning. The three classes obtained correlated well with the lithological units present in the area and, from their relationship, it was possible to deduce structural elements not yet well understood, providing new perspectives in the characterization of the Alhama de Murcia fault zone. Research supported by grants: VECTOR EU project ID 101058483, and SIT4ME -EITRawMaterials.

How to cite: Hernandez i Pineda, A., Feyzullayev, T., Marzan, I., Alcalde, J., Martí, D., and Carbonell, R.: Unsupervised clustering to jointly interpret geophysical datasets across the Alhama de Murcia active fault, Spain., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13509, https://doi.org/10.5194/egusphere-egu23-13509, 2023.

SE Iberia is a tectonically active area with an important history of destructive earthquakes. Some of these earthquakes have been associated with known active faults, but the seismic source of most of them remains unclear. The majority of these earthquakes happened long before instrumental record began, so we can only study them through paleoseismology and/or historical records. In some cases, due to current soil usage, paleoseismic studies are extremely difficult to perform and researchers can only rely on historical records. Such is the case of the 1804 Dalías earthquake.

In this communication our objective is double. First, we present a methodology which can be useful to constrain the seismic source of historical earthquakes for which only intensity data are available. And second, we apply this methodology to the 1804 Dalías earthquake in order to constrain its seismic source, which remains unclear up to this day. Our proposed methodology is a combination of Gasperini et al. (1999, 2010)’s and de Pro-Díaz et al. (2022)’s methods. Our methodology searches for the faults that are most plausible candidates for the earthquake rupture, then builds seismic scenarios for each candidate rupture and finally compares these scenarios with the observed intensity field in order to find the candidate with the best fit. Seismic scenarios are built using OpenQuake and ArcGIS software (although QGIS can be used as well). The candidate that generates the simulation which better resembles the observed intensity field is considered the best candidate and the one closest to the actual earthquake source.

For the 1804 Dalías earthquake, we consider different ruptures along the Loma del Viento Fault (LVF) and Llano del Águila Fault (LLAF) traces as candidate ruptures, including some combined ruptures along the two faults. Our results show that there are two almost equally best candidates: a full rupture of the whole inland extension of the LVF, and a combined rupture of this fault and the LLAF.

How to cite: de Pro-Díaz, Y., Martínez-Díaz, J. J., and Canora Catalán, C.: The 1804 Dalías earthquake: ranking seismic sources with the Boxer and seismic scenario methods in SE Iberia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14995, https://doi.org/10.5194/egusphere-egu23-14995, 2023.

Analysis of lithospheric deformation is key to understanding current tectonics and other active deformation processes. The Alceste project, conducted in the framework of the Résif Seismicity Transverse Action, aims at proposing an updated seismic hazard model in metropolitan France built from the most recent data and academic consensus. One of the contributions will come from geodetic observations through strain rate integration in seismotectonic zoning and seismic hazard models.

Most of Western Europe in general, and metropolitan France in particular, is located within the Eurasian Plate, which has very low deformation and seismicity rates. These GNSS-derived secular velocity field could be related to the combination of different deformation processes, with a minor contribution from plate tectonics (relative plate motions, mantle convection, etc), while most of the measured velocities could be explained by non-tectonic long-term or transient processes (gravitational motions, Glacial Isostatic Adjustment, erosion, anthropogenic deformation, etc). Some of these physical processes causing surface deformation also reflect stress changes at depth that may be associated with loading on active faults and seismicity. Properly mapping this deformation is therefore a key to better assess seismic hazard in slow straining areas.

In order (i) to assess the variability due to the diversity of the strain-rate calculation methods used in the scientific community and (ii) to test their capacity to resolve low-amplitude consistent surface deformation, we conduct a benchmark exercise. We build sets of synthetic velocity fields sampled at the existing GNSS permanent stations from the RENAG (REseau NAtional GNSS Permanent), RGP (Réseau GPS Permanent) and other permanent and non-permanent benchmarks. Our synthetic velocity fields have the same characteristics (noise, uncertainties) as the observed velocities in metropolitan France but they contain surface deformation signals from known physical processes (block rotations, fault elastic loading, large scale flexure, etc). We compare the strain rate invariants derived independently by nine different RENAG research teams (using different software) to the expected strain rate patterns and discuss drawbacks and advantages of each approach. In a second step, we analyzed the strain rate tensors derived from the synthetic velocity fields to discuss potential regional style of the deformation in metropolitan France. Previous studies have shown that the computation of strain rate tensors is impacted by the user-defined parameters and the algorithm specificity used. Exploring these different biases in the strain rate solutions represent the opportunity to improve the understanding of the conventional problem of the standard interpolation.

How to cite: Metois, M., Periollat, A., Mazzotti, S., Masson, F., Vergnolle, M., Socquet, A., Vernant, P., Rigo, A., Baize, S., Piña-Valdés, J., and Grosset, J.: Slowly deforming metropolitan France: what can GNSS tell about physical processes ?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17273, https://doi.org/10.5194/egusphere-egu23-17273, 2023.

We present a comparative study of the glacially induced fault reactivation within the Southern Baltic Sea since the Upper Saalian. A complex tectonic pattern characterizes the Tornquist Fan, which spans between the Tornquist Zone in the North and the Trans European Suture Zone in the South. Multiple fault zones result from the varying transpressional and transtensional stress activities since the Paleozoic. The current tectonic pattern of this unique natural laboratory is composed of several faults with varying strike and dip directions, depths and characters (normal, reverse, strike slip). Moreover, some shallow faults are associated with Zechstein salt pillows, and others are related to anticlines formed during the Cretaceous to Paleogene compression.

Using finite-element simulations of different glacial isostatic adjustment models (varying the material parameters in the Earth and the ice history), we obtained glaciation induced Coulomb failure stress changes (∆CFS) at the faults over time, covering the past 200 ka. Comparing the activation potential of several faults of different tectonic background reveals the impact of the varying crustal and fault properties, as well as the influence of salt structures below. Besides lateral differences in the ∆CFS due to the changing geology, we see temporal differences, by comparing the occurrence of glacially induced faulting with different ice advances.

How to cite: Seidel, E., Steffen, H., Steffen, R., Ahlrichs, N., and Hübscher, C.: 200 000 years of glacially induced faulting in the Tornquist Fan area, SW Baltic Sea., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14350, https://doi.org/10.5194/egusphere-egu23-14350, 2023.

In Northern Andes, oblique subduction of the Nazca plate below the South America Plate induces a northward motion of the North Andean Sliver, at a rate of ~10 mm/yr with respect to Stable South America. In Ecuador in particular, the associated strain is mainly accomodated along the large Chingual-Cosanga-Puna-Pallatanga (CCPP) fault system, which hosted several 7+ magnitude earthquakes in the historical period. Recent studies using block-modeling of GNSS data raise important questions about the partitioning and the localization of the deformation both inside and at the limits of the North-Andean sliver. Therefore, time-series analysis of InSAR data, allowing a large spatial resolution, would complement the existing geodetic dataset of observation of low-rate crustal motions in this region. Taking advantage of 7 to 8 years of Sentinel-1 archive, we compute long time-series of InSAR data for the whole Interandean region of Ecuador (~100 by 400 km), using the NSBAS processing chain. Because processing of InSAR data in this ecuatorial region raises several challenges, such as low-coherence due to vegetation, ionospheric and troposheric noise, and fading signals,we develop strategies to mitigate the noise terms. By using an optimized interferogram network, improvedweighting during multilooking, and a temporal decomposition of the time-series, we produce the first InSAR velocity maps of the Ecuadorian Cordilleras. We then compare these results to the existing block-model derived from GNSS horizontal data in order to evaluate the possibility of characterizing the motion of North Andean Sliver with an increased spatial resolution.

How to cite: Marconato, L., Doin, M.-P., Audin, L., Harrichhausen, N., Nocquet, J.-M., Jarrin, P., and Rolandone, F.: Can we observe North Andean Sliver motion using long InSAR time-series analysis?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5686, https://doi.org/10.5194/egusphere-egu23-5686, 2023.

This work presents a review of some methods for seismic hazard assessments based on hybrid source models, composed of active faults and seismic zones. These approaches are applied in a slow deformation area, defined as areas where the slip rate of the active faults is slower than 5 mm/yr.

The introduction of active faults as independent seismic sources in seismic hazard assessment has a great impact on the results that can be obtained in urban areas close to active faults, with respect with those obtained with classical zoning methods (CZM). 

Currently, there are no widely contrasted methodological developments to include zones and the characterized active faults in the source models, especially in slow deforming areas. Even though, some approaches that have used hybrid models (HM) composed of zone-type sources and fault-type sources, revealed that expected ground motion values around main faults may double (on average) those obtained by zoned models, in agreement with observations in recent earthquakes (Rivas-Medina, A., 2018; Gómez-Novell O., 2020).

This presentation compares some methods that address two key aspects: how to quantify the geological information and transfer it to recurrence models, and how to distribute the seismic potential between the two types of sources. Some of these methods are: 1) Moment-rate based method proposed by Bungum (2007), 2) Slip-rate based method also proposed by Bungum (2007), 3) Hybrid method developed by Rivas-Medina et al. (2019).

This study is centered in the Eastern Betics Shear Zone (EBSZ) in southeast Spain, which is a low to moderate seismicity region. These methods were applied in the seismic zones 37 and 55 defined by Garcia-Mayordomo (2015) due to the seismological and geological data availability of the present faults in each zone.

How to cite: Ornelas Agrela, A. F., Benito, M. B., and Lindholm, C.: Review of methods for characterization of active faults for seismic hazard purposes., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16439, https://doi.org/10.5194/egusphere-egu23-16439, 2023.