Constraining the point source parameters of the 11 November 2019 Mw 4.9 Le Teil earthquake using multiple relocation approaches, first motion and full waveform inversions

Delouis, Bertrand; Oral, Elif; Menager, Marine; Ampuero, J. P.; Trilla, Aurélie Guilhem; Régnier, Marc; Deschamps, A.

doi:10.5802/crgeos.78

Cited by 18 publications

(17 citation statements)

References 34 publications

(45 reference statements)

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“…InSAR offers the opportunity to study potential interactions between the earthquake slip and the pre-existing three-dimensional geological structure. The more recent relocations of the point source of the Le Teil earthquake by Delouis et al (2021) can be discussed together with our slip distribution. The epicentral area that they estimate is located between the western part of Le Teil quarry and the LRF (Fig.…”

Section: Potential Interactions Between 3d Geology Fault Geometry And...mentioning

confidence: 96%

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Insights on fault reactivation during the 2019 November 11, Mw 4.9 Le Teil earthquake in southeastern France, from a joint 3-D geological model and InSAR time-series analysis

Marconato

Leloup

Lasserre

et al. 2021

Geophysical Journal International

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Summary The 2019, Mw4.9 Le Teil earthquake occurred in south-eastern France, causing substantial damage in this slow deforming region. Field observations, remote sensing and seismological studies following the event revealed that coseismic slip concentrates at shallow depth along a ∼5 km long rupture associated with surface breaks and a thrusting mechanism. We further investigate this earthquake by combining geological field mapping, 3D geology, InSAR time series analysis and a coseismic slip inversion. From structural, stratigraphic and geological data collected around the epicenter, we first produce a 3D geological model of the region surrounding the rupture using the GeoModellerTM software. Our model includes the geometry of the geological layers and of the main faults, including the La Rouvière Fault, the Oligocene normal fault that ruptured during the earthquake. We generate a time series of surface displacement from Sentinel-1 SAR data ranging from early January 2019 to late January 2020 using the NSBAS processing chain. The spatio-temporal patterns of surface displacement for this time span show neither a clear pre-seismic signal nor significant post-seismic transient deformation. We extract the coseismic displacement pattern from the InSAR time series, highlighting along-strike variations of coseismic surface slip. The maximum relative displacement along the Line-Of-Sight is up to ∼16 cm and is located in the southwestern part of the rupture. We invert for the slip distribution on the fault from the InSAR coseismic surface displacement field. Constraining our fault geometry from the geological model, acceptable fault dip ranges between 55° and 60°. Our model confirms the reactivation of La Rouvière fault, with reverse slip at very shallow depth and two main slip patches reaching respectively 30 cm and 24 cm of slip, both around 500 m depth. We finally discuss how the 3D fault geometry and geological structure may have impacted the slip distribution and propagation during the earthquake. This study is a step to reassess the seismic hazard of the many faults similar to the La Rouvière one along the Cévennes fault system, in a densely populated area hosting several sensitive nuclear sites.

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Section: Potential Interactions Between 3d Geology Fault Geometry And...mentioning

confidence: 96%

“…2. Revised location of epicenter (yellow star in a) and focal mechanism are from Delouis et al (2021).…”

Section: Introductionmentioning

confidence: 99%

Insights on fault reactivation during the 2019 November 11, Mw 4.9 Le Teil earthquake in southeastern France, from a joint 3-D geological model and InSAR time-series analysis

Marconato

Leloup

Lasserre

et al. 2021

Geophysical Journal International

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Section: Bridging Disciplinesmentioning

confidence: 99%

“…In a separate project, existing data are being made available at the national level, beyond the existing synthesis 2 , and updated with regional input. Interdisciplinary cooperation has sprung up between geologists, seismologists and geophysicists from academic circles, to develop temporary instrumental networks and propose analyses of the earthquake and consequences [3][4][5][6][7] .Field geologists have continued to investigate where possible, despite the lockdowns and curfews resulting from the COVID-19 pandemic, and the motivation of our group has remained strong. Importantly, we were able to excavate a dozen paleoseismological trenches that demonstrate earlier incidences of ground rupture.…”

mentioning

confidence: 99%

Post-publication careers: ground ruptured, community united

Baize

Ritz

2022

Commun Earth Environ

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When an earthquake in southern France caused the ground to rupture-a phenomenon not known during the last 25 years in the region-the earthquake science community worked together to determine the implications for hazard assessment. Now we must maintain that spirit of co-operation for the future.In the most destructive French earthquake since 1967, the ground ruptured at the surface (Fig. 1) -just a few kilometers from a nuclear power plant. The event occurred near the small town of Le Teil, southeastern France on November 11, 2019, and constitutes a phenomenon that had not previously been described in France. At Mw 4.9, the quake was only moderate in magnitude, but occurred at a depth between 1 and 2 km, then lead to the ground rupture.The event captured our interest along with that of the French scientific community, and we published an early account that identified and described this surface rupture in Communications Earth & Environment in late August 2020 1 . French society, unaccustomed to such destructive earthquakes in metropolitan France joined the conversation. Bridging disciplinesIn the wake of the quake, the community of geologists interested in earthquakes and in the characterization of faults in France has come together to take action. Two PhD theses have been assigned to investigate the Cévennes Fault that was responsible for the Le Teil earthquake, supported by industrial and governmental agencies. In a separate project, existing data are being made available at the national level, beyond the existing synthesis 2 , and updated with regional input. Interdisciplinary cooperation has sprung up between geologists, seismologists and geophysicists from academic circles, to develop temporary instrumental networks and propose analyses of the earthquake and consequences [3][4][5][6][7] .Field geologists have continued to investigate where possible, despite the lockdowns and curfews resulting from the COVID-19 pandemic, and the motivation of our group has remained strong. Importantly, we were able to excavate a dozen paleoseismological trenches that demonstrate earlier incidences of ground rupture. Some trenches are still open for 2021/ 2022 scientific conferences, field trips and for teaching: they are a crucial resource in a country were such events and research opportunities are not so common. All this was made possible thanks to the positive and enthusiastic response of land owners, a welcome behavioral trait in freshly earthquake-shaken areas.We have adapted our way of working to meet pandemic-related health requirements, an easier task in outdoor activity. We also had to satisfy the needs of co-working: we concentrated field efforts, as well as external media visits when restrictions allowed, and moved online conferences to exchange ideas to the phases of lockdown. Ultimately, we found that these adaptations allowed us to continue to carry out our time-sensitive work effectively.

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“…In the moment‐tensor catalog of the University of Patras for the WGoC (Serpetsidaki et al., 2016, 2021), from 2006 to 2020 (before the crisis), only three events of Mw > 4.5 had centroid depth shallower than 5 km. In general, only a few earthquakes of Mw ∼ 5 worldwide, and not only in normal‐faulting systems, have their slip localized at shallow depths ∼0–5 km (e.g., Champenois et al., 2017; Delouis et al., 2021; Ellsworth et al., 2019; Figueiredo et al., 2022; Liu & Zahradník, 2020; López‐Comino et al., 2016; Wei et al., 2013). As some of them are shallow due to anthropogenic (triggered/induced) origin, the causative structures responsible for the very shallow slip of the natural Feb17 event above the rift detachment are worth studying.…”

Section: Introductionmentioning

confidence: 99%

An Atypical Shallow Mw 5.3, 2021 Earthquake in the Western Corinth Rift (Greece)

et al. 2022

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Moderate‐to‐large earthquakes in rifts may occur on leading boundary faults or inner antithetic faults. Here we show a rare case of the 2020–2021 seismic sequence in the Corinth rift, that culminated in the shallow rupture of the antithetic fault, neither preceded nor followed by the leading fault rupture. The hypocenter of the largest shock (Mw 5.3 of 17 February 2021) was located at ∼8 km depth. However, seismic waveform data, supported by satellite‐geodetic and tide gauge measurements, pointed to rupture at shallow depth (∼3 km), where no earthquakes were previously observed. We show that the earthquake most probably ruptured two orthogonal, conjugate fault segments: a weak nucleation phase occurred in the microseismically highly active sub‐horizontal detachment layer, followed – a few seconds later – by a larger, shallow moment release on a high‐angle, south‐dipping normal fault. The latter is the Mornos offshore fault, antithetic to the leading, north‐dipping Psathopyrgos fault. Our study presents the first instrumental/observational evidence of a very shallow Mw 5+ event in this rift – and one of the few reported worldwide. The depth limit of the main shallow slip patch coincides with the expected crossing of the Mornos fault with the Psathopyrgos fault, stressing the importance of fault segmentation and rooting inherited from the rift history. This unusual shallow slip in a depth range with little background seismicity and few aftershocks needs to be further investigated by dynamic modeling as a possible prototype of hazardous events in rift environments.

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Constraining the point source parameters of the 11 November 2019 Mw 4.9 Le Teil earthquake using multiple relocation approaches, first motion and full waveform inversions

Abstract: Constraining the point source parameters of the 11 November 2019 Mw 4.9 Le Teil earthquake using multiple relocation approaches, first motion and full waveform inversions

Cited by 18 publications

References 34 publications

Insights on fault reactivation during the 2019 November 11, Mw 4.9 Le Teil earthquake in southeastern France, from a joint 3-D geological model and InSAR time-series analysis

Insights on fault reactivation during the 2019 November 11, Mw 4.9 Le Teil earthquake in southeastern France, from a joint 3-D geological model and InSAR time-series analysis

Post-publication careers: ground ruptured, community united

An Atypical Shallow Mw 5.3, 2021 Earthquake in the Western Corinth Rift (Greece)

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