Seismicity patterns in southwestern France

Abstract

Seismic monitoring of southwestern France began in the 1960s, and homogeneous coverage by observation networks has been in place since the 1990s. The accumulation of data now allows a refined understanding of regional seismicity, not only on its spatial aspects, but also on the regularity of the earthquake distribution over time. This paper is both a review of the work carried out on the subject, and a progress report on the current knowledge of the regional seismicity in its seismotectonic context. With the support of maps, the available catalogs are exploited at different nested scales, from the region as a whole to the numerous clusters that characterize the seismicity of southwestern France, and more specifically that of the Pyrenees. An exhaustive study of these Pyrenean clusters and their temporal behavior is proposed, allowing in particular a better description of the prominent seismicity stripe to the northwest of the range.

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

“…At a large scale (∼600 km 2 , Figs 2a-c), a general dipping of the seismicity towards the northeast is observed (Azim ∼30 • , dip ∼40 • ), which is consistent with the long-term features of the seismicity (Sylvander et al 2021). Most of the deep seismicity (>15 km) is found below the North Pyrenean Fault (red dots, Fig.…”

“…This seismicity is preferentially organized in the form of clusters, more intense in the central and western parts of the chain (Sylvander et al 2021). Since spring 2020, two new seismicity clusters have appeared on the periphery of the active regions highlighted by Sylvander et al (2021) in the central French Pyrenees. They are located in the Gripp valley and are not geographically connected to the clusters identified until then (Fig.…”

“…At the boundary between the Eurasian and Iberian lithospheric plates, the Pyrenees has a moderate and well-documented crustal seismicity (see Sylvander et al 2021, for a review). This seismicity is preferentially organized in the form of clusters, more intense in the central and western parts of the chain (Sylvander et al 2021).…”

“…At the boundary between the Eurasian and Iberian lithospheric plates, the Pyrenees has a moderate and well-documented crustal seismicity (see Sylvander et al 2021, for a review). This seismicity is preferentially organized in the form of clusters, more intense in the central and western parts of the chain (Sylvander et al 2021). Since spring 2020, two new seismicity clusters have appeared on the periphery of the active regions highlighted by Sylvander et al (2021) in the central French Pyrenees.…”

New CNN-based tool to discriminate anthropogenic from natural low magnitude seismic events

“…In metropolitan France, instrumental seismicity is mostly characterized by low magnitude earthquakes (Cara et al 2015). The deployment of new permanent stations since mid-2018 (Beucler et al 2021;Doubre et al 2021;Larroque et al 2021;Sylvander et al 2021) has conducted to an increase in the number of detected natural and anthropogenic seismic events. However, metropolitan seismicity is now dominated by the detection of anthropogenic events (for instance, see fig.…”