Unprecedented seismic swarm in the Maurienne valley (2017–2019) observed by the SISmalp Alpine seismic network: operational monitoring and management

Guéguen, Philippe; Janex, Gaël; Nomade, Jérôme; Langlais, Mickaël; Helmstetter, Agnès; Coutant, Olivier; Schwartz, Stéphane; Dollet, Cyrielle

doi:10.5802/crgeos.70

Cited by 5 publications

(13 citation statements)

References 53 publications

(59 reference statements)

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“…The position of events matches with the geometry and position of the nearby Fond de France Fault system (Figure 1). The same structure can also be observed by simply relocating the original catalog as shown by Guéguen et al (2021) (Figures 2a and 2b).…”

Section: Event Relocationsupporting

confidence: 63%

“…These errors are smaller than the errors affecting the events relocated by Guéguen et al. (2021) (175, 138, and 164 m). Among the 2048 relocated events, it was possible to select a reference event for 808 out of the previously defined 1,330 clusters.…”

Section: Resultsmentioning

confidence: 50%

“…This suggests that during the swarm, fault systems with different geometries were reactivated. Previous studies (Guéguen et al, 2021) do not report any focal mechanism for the shallow events, and for this reason, we cannot derive any additional information on their faulting style. Geological studies show the presence of 120°N-striking normal faults, which do not match with the strike of the clusters, but they indicate that in the region different sets of faults are possible, and the possibility of fault geometries yet to be discovered cannot be excluded.…”

Section: Discussionmentioning

confidence: 91%

“…In this paper, we expand the SeisComP3 catalog and the catalog of Guéguen et al. (2021) by applying template matching. We also relocate the new detections and estimate their moment magnitude.…”

Section: Introductionmentioning

confidence: 99%

“…Starting from a catalog built using SeisComP3 (Weber et al, 2007), they relocated the earthquakes with a double-difference method, calculated focal mechanisms, and provided a preliminary description of the fault system reactivated during the swarm. In this paper, we expand the SeisComP3 catalog and the catalog of Guéguen et al (2021) by applying template matching. We also relocate the new detections and estimate their moment magnitude.…”

mentioning

confidence: 99%

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Analysis of the Spatiotemporal Evolution of the Maurienne Swarm (French Alps) Based on Earthquake Clustering

Minetto

Helmstetter

Schwartz

et al. 2022

Earth and Space Science

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A seismic swarm is generally defined as a seismic sequence with no clear dominant earthquake (mainshock) (Mogi, 1963). Seismic swarms also do not have a clear onset, and the number of events do not decrease with time according to the Omori law (Utsu, 1957) as observed in classical mainshock-aftershock sequences. This suggests that stress triggering (Stein, 1999) alone cannot explain the genesis of seismic swarms. Seismic swarms are observed in many geological environments, such as volcanic and hydrothermal regions (Hill, 1977), oceanic ridges (Sykes, 1970), pure tectonic regions (e.g., Špičák, 2000), and also during hydraulic stimulations (Healy et al., 1968).Fluids are commonly cited as one of the driving sources of seismic swarms. Pore fluid pressure would indeed lower the effective stress, thus promoting rupture (Hubbert & Rubey, 1959). This is supported by experiments during fluid injections (e.g., Ohtake, 1974;Raleigh et al., 1976), and by the observation of changes in groundwater level and surface discharge during seismic activity (Kisslinger, 1975). In instances of natural swarms where no subsurface effects are evident, a migration of seismicity compatible with fluid diffusion is the main indicator of the presence of fluids (e.g., Chen et al., 2012;Shelly et al., 2013).Aseismic slip is another proposed triggering mechanism of swarms, which is commonly inferred by comparing geodetic and seismological observations (Lohman & McGuire, 2007;Ozawa et al., 2007). Swarms caused by aseismic slip have a higher migration velocity (km/h) (Lohman & McGuire, 2007;Roland & McGuire, 2009) compared to seismic swarms caused by fluids (m/day) (Shapiro et al., 1997). The periodic occurrence of identical events called repeaters is also thought to be evidence of aseismic slip (e.g., Nadeau et al., 1995), but it has been shown that repeaters are also possible during fluid diffusion (Deichmann et al., 2014). Fluid diffusion and aseismic slip may also coexist (e.g., Bourouis & Bernard, 2007;De Barros et al., 2020;Hatch et al., 2020), and earthquake-earthquake interactions may also play a role in the migration (e.g., Fischer & Hainzl, 2021). Even though several triggering mechanisms have been proposed, it remains a challenge to identify the driving processes of a swarm and to explain the reason why a swarm has a specific migration velocity, propagation direction, and duration.The lack of understanding of why seismic swarms occur does not only derive from the complexity of the processes, but also from specific difficulties inherent to these seismic sequences. Studying the spatiotemporal evolution of swarms requires high-resolution locations and high detection rates, usually obtained with template matching

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Section: Event Relocationsupporting

confidence: 63%

Section: Resultsmentioning

confidence: 50%

Section: Discussionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Analysis of the Spatiotemporal Evolution of the Maurienne Swarm (French Alps) Based on Earthquake Clustering

Minetto

Helmstetter

Schwartz

et al. 2022

Earth and Space Science

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Fluid-driven seismic swarms in the Gripp valley (Haute-Pyrénées, France)

Derode

Gounon

Letort

et al. 2023

Geophysical Journal International

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Summary An unusual seismic activity has recently occurred in the Gripp valley, located in the central part of the French Pyrenees. Since spring 2020, two new swarms appeared, clearly outside the usual location of the seismicity in this area. On September 20, 2020, almost concomitantly with the activation of the second seismic swarm, a hole suddenly opened in the bed of a local river, the Adour de Payolle. This hole drained the water from the river, which dried up over 500 m. We follow and study the spatial and temporal evolution of these clusters, using four temporary stations deployed a few days or months after the beginning of the crisis to complete the regional network. These additional data lead to the construction of a comprehensive catalog of more than 4900 earthquakes, using both a template matching approach and a deep-learning based phase picking method to complete and improve the initial catalog available from the French seismological agency. This allows highlighting a slow and clear migration of the seismicity during one year. Precise absolute and relative event locations reveal a dipping faulting structure, confirmed by the focal mechanism estimated for the highest magnitude event of the sequence (ML 3). We propose to explain the observed migration of the seismicity by deep fluids going up through a newly discovered faulting structure.

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Using In-Building Observations of Small-to-Large Earthquakes to Predict the Seismic Response of Structures

Guéguen,

Astorga

2024

Bulletin of the Seismological Society of America

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The main goal of this study is to evaluate the potential value of data from weak-to-moderate earthquakes for structural response analysis. Data recorded over 18 yr by the seismic network installed in the 12-stories Grenoble City Hall Building (France) is considered. The building response is analyzed in terms of intensity measures and engineering demand parameters, and then compared with strong earthquake data recorded in Japanese buildings. The uncertainties of structural response prediction are estimated and defined in terms of “within-building” and “between-building” components in the same way as the components of the ground-motion model. Data complementarity in the response model is observed between the weak-to-moderate (France) and the moderate-to-strong (Japan) earthquake datasets, disclosing nonlinear processes (associated with resonance period elongation) that are activated in buildings during low-to-strong motion. For example, fundamental frequency shifts are triggered at low values of both total structural drift amplitudes and equivalent strain rates (i.e., time derivative of structural drift). In addition, strain rate thresholds from 10−11 s−1 to 10−5 s−1 representing different structural conditions from undamaged to severely damaged buildings are observed to activate nonlinearities. This confirms the link between loading rates and structural conditions. Our results highlight the interest in instrumentation in buildings located in regions of weak-to-moderate seismicity, for (1) the development and calibration of realistic models for predicting the seismic response of structures, (2) for improving our understanding of the components of uncertainties in the risk assessment of existing buildings, and (3) to investigate physical processes activated in structures during seismic loading that influence their response.

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Unprecedented seismic swarm in the Maurienne valley (2017–2019) observed by the SISmalp Alpine seismic network: operational monitoring and management

Cited by 5 publications

References 53 publications

Analysis of the Spatiotemporal Evolution of the Maurienne Swarm (French Alps) Based on Earthquake Clustering

Analysis of the Spatiotemporal Evolution of the Maurienne Swarm (French Alps) Based on Earthquake Clustering

Fluid-driven seismic swarms in the Gripp valley (Haute-Pyrénées, France)

Using In-Building Observations of Small-to-Large Earthquakes to Predict the Seismic Response of Structures

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