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 8 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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The catalogue of 1987–2023 earthquakes in the western (French) Alps north of 43.5°N

Langlais,

Janex,

Guéguen

et al. 2024

Sci Data

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The western Alpine belt is the focal point of moderate but constant seismic activity. Numerous geodynamic and seismological studies underline the many scientific questions linked to Alpine dynamic processes and the associated rate of deformation resulting from late continental collision phases, and the assessment of seismic hazard and its associated risks. Seismic monitoring in the northern French Alps was launched in 1987 with the installation of the first seismological network, hosted by the Earth Science Observatory at Grenoble Alpes University. Since then, the network has been updated over the years, keeping pace with technical developments in seismic instrumentation, monitoring and data management. The homogenization of information described in this scientific data paper is motivated by the need for a single instrumental seismic catalogue, consisting in arrival times picks and hypocenters using the same velocity model. The final catalogue SISMalp-1987–2023 (CC-BY-4.0) contains 50,822 weak-to-moderate earthquakes with local magnitude between −1.8 and 5.0; it can serve as a basis for all general seismotectonic and risk assessment studies in the region.

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

Cited by 8 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

The catalogue of 1987–2023 earthquakes in the western (French) Alps north of 43.5°N

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

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