Full characterization of the ML 5.4 2019/11/11 Le Teil earthquake in France based on a multi-technology approach

2020 ◽  
Author(s):  
Amaury Vallage ◽  
Laurent Bollinger ◽  
Yoann Cano ◽  
Johann Champenois ◽  
Clara Duverger ◽  
...  
Keyword(s):  
Focal Mechanism ◽  
Ground Deformation ◽  
Waveform Inversion ◽  
Normal Fault ◽  
Fault System ◽  
Tectonic Deformation ◽  
Reverse Fault ◽  
Ground Shaking ◽  
Full Characterization ◽  
Stable Continental Region

<p>Metropolitan France is a region of slow tectonic deformation rates with sparse historical and instrumental seismicity, and where geodesy is not able to reach the required resolution in order to resolve the tectonic loadings. The few faults recognized as potential active rely on rare neotectonic slip rates, often integrated over geological scales.</p><p>In this context, the M<sub>L</sub> 5.4 Le Teil 2019 earthquake is of particular interest because it is the largest seismic event recorded in metropolitan France in the last 16 years. The last regional earthquake with a larger magnitude was the Lambesc event that occurred in 1909 about 110 km away from Le Teil epicenter. This recent earthquake offers a noteworthy opportunity to combine different technologies: seismological observations (RESIF and CEA) with satellite InSAR data and infrasound measurements, to help characterizing this stable continental region.</p><p>The analysis shows that the focal mechanism determined from the full waveform inversion of long-period seismological data is consistent with the activation of a reverse fault with a strike around 45°N and is associated with a moment magnitude of 4.8. Moreover, this event produced infrasound signals recorded by the OHP Alpine array located 110 km away. The analysis of these signals provides evidence of ground-to-air coupling in the epicentral region as well as ground shaking information.</p><p>Despite the moderate magnitude of the event, the ground deformation is resolved by InSAR with Sentinel-1 data. The interferogram is consistent with the shallow depth inverted from seismology and confirmed by the presence of surface ruptures. The inversion of multiple InSAR tracks allows characterizing the displacement at depth and along strike on the fault plane. The results are consistent with the focal mechanism derived from seismology. The earthquake has ruptured a 5-km long by ~1.5-km deep fault. The displacement reaches a maximum at a shallow 1 km-depth. The source inverted from InSAR coincides with the Rouvière fault, a branch of the Cévennes fault system formerly known as a normal fault. This reverse earthquake might be an example of an inherited structure re-activation as it is often the case in intraplate regions with polyphased history.</p>

scholarly journals Neogene-Quaternary tectonic regime and macroseismic observations in the Tyrnavos-Elassona broader epicentral area of the March 2021, intense earthquake sequence

2021 ◽  
Vol 58 ◽  
pp. 200
Author(s):  
Dimitrios Galanakis ◽  
Sotiris Sboras ◽  
Garyfalia Konstantopoulou ◽  
Markos Xenakis
Keyword(s):  
Normal Fault ◽  
Fault Scarp ◽  
Focal Mechanisms ◽  
Fault System ◽  
Spatiotemporal Evolution ◽  
Surface Rupture ◽  
Alluvial Deposits ◽  
Epicentral Area ◽  
Ground Shaking ◽  
Macroseismic Observations

On March 3, 2021, a strong (Mw6.3) earthquake occurred near the towns of Tyrnavos and Elassona. One day later (March 4), a second strong (Mw6.0) earthquake occurred just a few kilometres toward the WNW. The aftershock spatial distribution and the focal mechanisms revealed NW-SE-striking normal faulting. The focal mechanisms also revealed a NE-SW oriented extensional stress field, different from the orientation we knew so far (ca. N-S). The magnitude and location of the two strongest shocks, and the spatiotemporal evolution of the sequence, strongly suggest that two adjacent fault segments were ruptured respectively. The sequence was followed by several coseismic ground deformational phenomena, such as landslides/rockfalls, liquefaction and ruptures. The landslides and rockfalls were mostly associated with the ground shaking. The ruptures were observed west of the Titarissios River, near to the Quaternary faults found by bore-hole lignite investigation. In the same direction, a fault scarp separating the alpidic basement from the alluvial deposits of the Titarissios valley implies the occurrence of a well-developed fault system. Some of the ground ruptures were accompanied by extensive liquefaction phenomena. Others cross-cut reinforced concrete irrigation channels without changing their direction. We suggest that this fault system was partially reactivated, as a secondary surface rupture, during the sequence as a steeper splay of a deeper low-to-moderate angle normal fault.

scholarly journals The 31 March 2020 Mw 6.5 Stanley, Idaho, Earthquake: Seismotectonics and Preliminary Aftershock Analysis

2020 ◽  
Author(s):  
Lee M. Liberty ◽  
Zachery M. Lifton ◽  
T. Dylan Mikesell
Keyword(s):  
Surface Displacement ◽  
Volcanic Belt ◽  
Normal Fault ◽  
Fault System ◽  
Basin And Range Province ◽  
Ground Shaking ◽  
The North ◽  
Show Evidence ◽  
Tectonic Framework ◽  
Tectonic Belt

Abstract We report on the tectonic framework, seismicity, and aftershock monitoring efforts related to the 31 March 2020 Mw 6.5 Stanley, Idaho, earthquake. The earthquake sequence has produced both strike-slip and dip-slip motion, with minimal surface displacement or damage. The earthquake occurred at the northern limits of the Sawtooth normal fault. This fault separates the Centennial tectonic belt, a zone of active seismicity within the Basin and Range Province, from the Idaho batholith to the west and Challis volcanic belt to the north and east. We show evidence for a potential kinematic link between the northeast-dipping Sawtooth fault and the southwest-dipping Lost River fault. These opposing faults have recorded four of the five M≥6 Idaho earthquakes from the past 76 yr, including 1983 Mw 6.9 Borah Peak and the 1944 M 6.1 and 1945 M 6.0 Seafoam earthquakes. Geological and geophysical data point to possible fault boundary segments driven by pre-existing geologic structures. We suggest that the limits of both the Sawtooth and Lost River faults extend north beyond their mapped extent, are influenced by the relic trans-Challis fault system, and that seismicity within this region will likely continue for the coming years. Ongoing seismic monitoring efforts will lead to an improved understanding of ground shaking potential and active fault characteristics.

scholarly journals A functional tool to explore the reliability of micro-earthquake focal mechanism solutions for seismotectonic purposes

Solid Earth ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 65-83
Author(s):  
Guido Maria Adinolfi ◽  
Raffaella De Matteis ◽  
Rita de Nardis ◽  
Aldo Zollo
Keyword(s):  
Focal Mechanism ◽  
Fault Plane ◽  
Normal Fault ◽  
Focal Mechanisms ◽  
Seismic Network ◽  
Fault System ◽  
Fault Plane Solutions ◽  
Stress Regime ◽  
Focal Mechanism Solutions ◽  
Earthquake Focal Mechanism

Abstract. Improving the knowledge of seismogenic faults requires the integration of geological, seismological, and geophysical information. Among several analyses, the definition of earthquake focal mechanisms plays an essential role in providing information about the geometry of individual faults and the stress regime acting in a region. Fault plane solutions can be retrieved by several techniques operating in specific magnitude ranges, both in the time and frequency domain and using different data. For earthquakes of low magnitude, the limited number of available data and their uncertainties can compromise the stability of fault plane solutions. In this work, we propose a useful methodology to evaluate how well a seismic network, used to monitor natural and/or induced micro-seismicity, estimates focal mechanisms as a function of magnitude, location, and kinematics of seismic source and consequently their reliability in defining seismotectonic models. To study the consistency of focal mechanism solutions, we use a Bayesian approach that jointly inverts the P/S long-period spectral-level ratios and the P polarities to infer the fault plane solutions. We applied this methodology, by computing synthetic data, to the local seismic network operating in the Campania–Lucania Apennines (southern Italy) aimed to monitor the complex normal fault system activated during the Ms 6.9, 1980 earthquake. We demonstrate that the method we propose is effective and can be adapted for other case studies with a double purpose. It can be a valid tool to design or to test the performance of local seismic networks, and more generally it can be used to assign an absolute uncertainty to focal mechanism solutions fundamental for seismotectonic studies.

scholarly journals Deformation patterns in the Van region (Eastern Turkey) and their significance for the tectonic framework

2019 ◽  
Vol 70 (3) ◽  
pp. 193-208 ◽  
Author(s):  
M. Alper Şengül ◽  
Şule Gürboğa ◽  
İsmail Akkaya ◽  
Ali Özvan
Keyword(s):  
Principal Stress ◽  
Normal Fault ◽  
Field Work ◽  
Fault System ◽  
Deformation Pattern ◽  
Reverse Fault ◽  
Principal Stress Direction ◽  
Stress Direction ◽  
Eastern Turkey ◽  
Deformation Patterns

Abstract The area of investigation is located on the south-eastern shore of Lake Van in Eastern Turkey where a destructive earthquake took place on 23rd October, 2011 (Mw = 7.1). Following the earthquake, different source mechanisms, deformations, and types of faulting have been suggested by different scientists. In this research, Edremit district and vicinities located on the southern side of Van have been investigated to understand the deformation pattern in a travertine (400 ka) formation on the surface, and its structural and stratigraphic relationships with the main faults under the surface by using two-dimensional (2D) Electrical Resistivity Tomography (ERT) profiles. The results were used to document the deformation pattern of rocks with the Miocene and the Holocene (400 ka travertine) in ages. By means of the investigations, deformation patterns implying the tectonic regimes during the Oligocene–Miocene–Pliocene, and Quaternary time have been determined. According to detailed field work, the local principal stress direction has been defined as approximately N 35° W. This is also supported by the joint set and slip-plane data. Moreover, Oligocene– Miocene units provide a similar principal stress direction. Our data suggest that the southern part of the Elmalık fault is characteristic of reverse faults rather than of the normal fault system that has been previously reported. In addition, the Gürpınar fault controlling the deformation patterns of the region is a reverse fault with dextral component.

Analyzing the paleoseismic history of the La Rouvière fault, unexpected source of the 11-11-2019, Mw4.9 Le Teil surface rupturing earthquake (Cévennes fault system, France) 

2021 ◽  
Author(s):  
Jean-François Ritz ◽  
Stéphane Baize ◽  
Matthieu Ferry ◽  
Estelle Hannouz ◽  
Magali Riesner ◽  
...  
Keyword(s):  
Normal Fault ◽  
Fault System ◽  
Quaternary Deposits ◽  
Quaternary Period ◽  
Ground Shaking ◽  
Aeolian Deposits ◽  
Reverse Faulting ◽  
History Of ◽  
Region 10 ◽  
First Time

<p>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. <span><span data-language-to-translate-into="fr" data-phrase-index="0">All of this information raises the question of whether the fault was reactivated for the first time since the Oligocene during the Teil earthquake, </span></span>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.</p><p>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<sup>-9</sup> yrs<sup>-1</sup>). 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.</p>

Erosion rates of the New Zealand Southern Alps reflect long-term tectonics and transient climate

2021 ◽  
Author(s):  
Duna Roda-Boluda ◽  
Taylor Schildgen ◽  
Hella Wittmann-Oelze ◽  
Stefanie Tofelde ◽  
Aaron Bufe ◽  
...  
Keyword(s):  
New Zealand ◽  
Strike Slip ◽  
Southern Alps ◽  
Fault System ◽  
Tectonic Deformation ◽  
Seismic Cycle ◽  
Erosion Rates ◽  
Alpine Fault ◽  
Oblique Convergence

<p>The Southern Alps of New Zealand are the expression of the oblique convergence between the Pacific and Australian plates, which move at a relative velocity of nearly 40 mm/yr. This convergence is accommodated by the range-bounding Alpine Fault, with a strike-slip component of ~30-40 mm/yr, and a shortening component normal to the fault of ~8-10 mm/yr. While strike-slip rates seem to be fairly constant along the Alpine Fault, throw rates appear to vary considerably, and whether the locus of maximum exhumation is located near the fault, at the main drainage divide, or part-way between, is still debated. These uncertainties stem from very limited data characterizing vertical deformation rates along and across the Southern Alps. Thermochronology has constrained the Southern Alps exhumation history since the Miocene, but Quaternary exhumation is hard to resolve precisely due to the very high exhumation rates. Likewise, GPS surveys estimate a vertical uplift of ~5 mm/yr, but integrate only over ~10 yr timescales and are restricted to one transect across the range.</p><p>To obtain insights into the Quaternary distribution and rates of exhumation of the western Southern Alps, we use new <sup>10</sup>Be catchment-averaged erosion rates from 20 catchments along the western side of the range. Catchment-averaged erosion rates span an order of magnitude, between ~0.8 and >10 mm/yr, but we find that erosion rates of >10 mm/yr, a value often quoted in the literature as representative for the entire range, are very localized. Moreover, erosion rates decrease sharply north of the intersection with the Marlborough Fault System, suggesting substantial slip partitioning. These <sup>10</sup>Be catchment-averaged erosion rates integrate, on average, over the last ~300 yrs. Considering that the last earthquake on the Alpine Fault was in 1717, these rates are representative of inter-seismic erosion. Lake sedimentation rates and coseismic landslide modelling suggest that long-term (~10<sup>3</sup> yrs) erosion rates over a full seismic cycle could be ~40% greater than our inter-seismic erosion rates. If we assume steady state topography, such a scaling of our <sup>10</sup>Be erosion rate estimates can be used to estimate rock uplift rates in the Southern Alps. Finally, we find that erosion, and hence potentially exhumation, does not seem to be localized at a particular distance from the fault, as some tectonic and provenance studies have suggested. Instead, we find that superimposed on the primary tectonic control, there is an elevation/temperature control on erosion rates, which is probably transient and related to frost-cracking and glacial retreat.</p><p>Our results highlight the potential for <sup>10</sup>Be catchment-averaged erosion rates to provide insights into the magnitude and distribution of tectonic deformation rates, and the limitations that arise from transient erosion controls related to the seismic cycle and climate-modulated surface processes.</p><p> </p><p> </p>

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