# Special issue Comptes-Rendus Geosciences for the 100 years of the BCSF “Seismicity in France”

Frédéric Masson, Carole Petit, Stéphane Mazzotti

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Frédéric Masson, Carole Petit, Stéphane Mazzotti. Special issue Comptes-Rendus Geosciences for the 100 years of the BCSF “Seismicity in France”. Comptes Rendus. Géoscience, 2021, 353 (S1), pp.1-4.
10.5802/crgeos.94. hal-03475058

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# Comptes Rendus
## Géoscience
### Sciences de la Planète

Frédéric Masson, Carole Petit and Stéphane Mazzotti

**Special issue Comptes-Rendus Geosciences for the 100 years of the BCSF "Seismicity in France"**

Online first, 8th December 2021

<https://doi.org/10.5802/crgeos.94>

Part of the Special Issue: Seismicity in France

Guest editors: Carole Petit (Université de Nice & CNRS, France),

Stéphane Mazzotti (Univ. Montpellier & CNRS, France) and Frédéric Masson

(Université de Strasbourg & CNRS, France)

© Académie des sciences, Paris and the authors, 2021.

Some rights reserved.

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This article is licensed under the

CREATIVE COMMONS ATTRIBUTION 4.0 INTERNATIONAL LICENSE.

http://creativecommons.org/licenses/by/4.0/
the spatial diversity of metropolitan and overseas France and the different time scales.

As an introduction, Roger [2021] presents the major role of E. and J.-P. Rothé in the rise of the BCSF from 1921 to the 1960s, followed by the more difficult period of the 1970s and 1980s when its hegemony was challenged. As a complement, Sira et al. [2021] show the evolution of macroseismic observation methods since 1921. These two articles form a rich and contrasted panorama of a century of BCSF history; history that fortunately continues today.

In a second part, a series of regional syntheses are presented that review the seismicity and its original seismotectonic context in France. Metropolitan France has been divided into four quadrants. The Southeast [Larroque et al., 2021] covers the Jura, the Bresse, the Rhone valley, the Southeast Basin, the Alps, the Ligurian Sea, and Corsica. The Southwest [Sylvander et al., 2021] covers the Pyrenees and a very large southwestern part of the Massif Central. The Aquitaine Basin has almost no seismicity. The Northwest [Beucler et al., 2021] covers all the territories north of the Aquitaine Basin to the English Channel, including the seismicity zones of the Atlantic coast from Oléron to Brittany and the northwest of the Massif Central. Finally, the Northeast [Doubre et al., 2021] covers eastern France (Rhine Graben, Vosges), as well as the Ardennes and Hainaut, up to the North Sea. These four articles, written by experts of these regions, compile all the available information on seismicity, on a large time scale, by placing it in its tectonic context. They are major synthesis works that will serve as reference for students and researchers working in the future on these regions. Generally speaking, they show that these regions, and thus metropolitan France, present a diversity of seismic behaviors that can be explained by the complexity of the different geological domains, with variable rheological characteristics and structural heritage at the scale of the crust, as well as by the joint action of different deformation mechanisms. In addition to these four syntheses, three articles are proposed on the Antilles [Massin et al., 2021], Reunion [Duputel et al., 2021], and Mayotte [Bertil et al., 2021]. Massin et al. [2021] propose a new catalog of 46703 earthquakes that synthesizes all existing catalogs by objectively selecting the preferred location. Their work shows the difficulty of

proposing a catalog of seismicity usable for characterizing the seismic hazard in the Antilles and the attention that must be paid in the analysis of the data. Duputel et al. [2021] present the diversity of seismicity in Reunion (tectonic events, volcano-tectonic earthquakes, volcanic tremors, long-period and very-long-period earthquakes) and the link with volcanic systems. Finally, Bertil et al. [2021] review the recent seismic crisis in Mayotte and its implication for the understanding of the seismotectonics of the Coromos archipelago.

The third part of the special issue presents methodological articles: How are data acquired, processed, and interpreted on different time scales? Jomard et al. [2021] present the SIFRANCE historical seismicity database, which contains exhaustive information and analyses on historical seismicity in metropolitan France. The article explains how these data are acquired, what is archived, what are the potential levers to enrich the database. It describes how this database can be used, and as or maybe more importantly, all the limitations that must be respected in the use of these data in order to avoid over-interpretation. This article can be associated with that of Stocchi et al. [2021], who, using the example of the Tour du Pin earthquake of 1889, present how data obtained by a combination of in situ observations and fragility characteristics of historical buildings can be used to improve the magnitude estimation for historical earthquakes. Poursoulis et al. [2021] explain what archeoseismicity is, a discipline that is finally quite recent, and how the back and forth between archeoseismologists and engineers permits, on the one hand, to characterize past earthquakes experienced by buildings and, on the other hand, to consider the preservation of these buildings in case of new earthquakes. Longer time scales are the domain of paleoseismology. Bellier et al. [2021] detail the work done on active French faults over the last 30 years. In addition to these four articles, we propose in this section three other articles, also on methodological topics. The first one by Ritz et al. [2021] discusses how potentially active faults must be studied today in order to address the complex questions of its past—and potentially future—earthquake activity, in light of the modern tools that can be used, from laboratory imaging to preliminary field measurements before potentially trenching. The second is a synthesis by Beauval and Bard [2021] on how
seismic hazard assessment studies have been carried
out in France. The goal of this paper is to provide
readers with an overview of the successive seismic
zoning in mainland France together with the associ-
ated background, as well as an overview of the prob-
abilistic seismic hazard studies performed in the last
30 years. The third by Rivera et al. [2021] presents the
collection of historical seismograms of the University
of Strasbourg, historically associated with the seis-
mological station installed by the Germans at the end
of the 19th century in the gardens of the university.
The collection covers the period 1903–1981.

In its fourth and final part, the special issue focuses on recent seismic events in metropolitan France. Three articles focus on the Le Teil earthquake. The first [Cornou et al., 2021] presents a synthesis of the first information obtained on this earthquake by the French scientific community, which was extremely mobilized, both by the deployment of instruments in the field and by numerous research works on the data. The second [Delouis et al., 2021] focuses on the characterization of the source of the earthquake through a multi-approach study. Finally, the last one [Schlupp et al., 2021] comes back in detail on the establishment of the macroseismic map of this event, the most important in terms of intensity (maximum intensity VIII) since Arette in 1967 for metropolitan France. For comparison, such intensities had been reached in Guadeloupe during the earthquake of Saintes in 2004 [BCSF, 2005]. The following two articles are interested in notable seismic swarms. Guéguen et al. [2021] present the seismic swarm triggered in 2017–2019 in the Maurienne Valley (French Alps), with more than 5000 events detected by the regional SISmalp network. In addition, the article also presents how the public management of the crisis was conducted with the authorities. Baques et al. [2021] review in detail all the seismicity of the Ubaye region, which is marked by seismic swarms as well as by more notable earthquakes. In their article, great effort is made on the analysis of the historical seismicity in relation with present-day observations. Schmittbuhl et al. [2021] present the induced and triggered seismicity below the city of Strasbourg from November 2019 to January 2021, in connection with the presence of a deep geothermal site in Vendenheim. Finally, the last article reviews the historical seismicity of the Tricastin region in the Rhone valley [Bollinger et al., 2021], a seismic-

ity for which the original mechanism is not yet clear.
This special issue, to which the best specialists
in French seismicity in metropolitan and overseas
France have contributed, aims to be a reference for
the use of the entire geosciences community inter-
ested in French seismicity issues, and not only the
seismology community! We hope that reading it will
allow everyone to appreciate the importance of the
work done in recent years on this subject, and to bet-
ter understand the difficulty of proposing a simple
image of seismicity, especially in mainland France.
This collection of articles should convince that there
is no single, simple cause of metropolitan seismicity,
that its understanding is a difficult task, and that re-
search on this subject needs to be widely supported.

References

Baques, M. et al. (2021). Seismic activity in Ubaye Region (French Alps): A specific behaviour highlighted by mainshocks and swarm sequences. *C. R. Géosci.* (in this issue).

BCSF (2005). Séisme des Saintes (Guadeloupe) du 21 novembre 2004, note préliminaire. BCSF2005-NP3, 62 pages, 101 figures, 28 tables, 5 annexes.

Beauval, C. and Bard, P.-Y. (2021). History of probabilistic seismic hazard assessment studies and seismic zonations in mainland France. *C. R. Géosci.* (in this issue).

Bellier, O. et al. (2021). Paleoseismic study in France, 30 years already! What can paleoseismology bring to the assessment of the seismic hazard in France? *C. R. Géosci.* (in this issue).

Bertil, D. et al. (2021). The unexpected Mayotte 2018–2020 seismic sequence: a reappraisal of the regional seismicity of the Comoros. *C. R. Géosci.* (in this issue).

Beucler, É. et al. (2021). Characteristics and possible origins of the seismicity in northwestern France. *C. R. Géosci.* (in this issue).

Bollinger, L. et al. (2021). Seismic swarms in Tricastin, lower Rhône Valley (France) : review of historical 1 and instrumental seismicity and models. *C. R. Géosci.* (in this issue).

Calais, E., Camelbeeck, T., Stein, S., Liu, M., and Craig, T. J. (2016). A new paradigm for large earthquakes in stable continental plate interiors. *Geophys. Res. Lett.*, 43, 10621–10637.
Cornou, C. et al. (2021). Rapid response to the $M_w$ 4.9 earthquake of November 11, 2019 in Le Teil, Lower Rhône Valley, France. *C. R. Géosci.* (in this issue).

Craig, T. J. and Calais, E. (2014). Strain accumulation in the New Madrid and Wabash Valley seismic zones from 14 years of continuous GPS observation. *J. Geophys. Res. Solid Earth*, 119. https://doi.org/10.1002/2014JB011498.

Delouis, B. et al. (2021). Constraining the point source parameters of the 11 November 2019 $M_w$ 4.9 Le Teil earthquake using multiple relocation approaches, first motion and full waveform inversions. *C. R. Géosci.* (in this issue).

Doubre, C. et al. (2021). Seismotectonics and geodynamic implication in North-Eastern France and neighboring regions. *C. R. Géosci.* (in this issue).

Duputel, Z. et al. (2021). Seismicity of La Réunion island. *C. R. Géosci.* (in this issue).

Guéguen, P. et al. (2021). Unprecedent seismic swarm in the Maurienne valley (2017–2019) observed by the SISmalp Alpine seismic network: operational monitoring and management. *C. R. Géosci.* (in this issue).

Henrion, E., Masson, F., Doubre, C., Ulrich, P., and Meghraoui, M. (2020). Present-day deformation in the Upper Rhine Graben from GNSS data. *Geophys. J. Int.*, 223(1), 599–611.

Jomard, H. et al. (2021). The SISFRANCE database of historical seismicity. State of the art and perspectives. *C. R. Géosci.* (in this issue).

Larroque, C. et al. (2021). Seismotectonics of south-east France: from the Jura mountains to Corsica. *C. R. Géosci.* (in this issue).

Leclère, H. and Calais, E. (2019). A parametric analysis of fault reactivation in the New Madrid seismic zone: the role of pore-fluid overpressure. *J. Geophys. Res.*, 124, 10630–10648.

Massin, F. et al. (2021). Automatic picking and probabilistic location for earthquake assessment in the

Lesser Antilles subduction zone (1972–2012). *C. R. Géosci.* (in this issue).

Masson, C., Mazzotti, S., Vernant, P., and Doerflinger, E. (2019). Extracting small deformation beyond individual station precision from dense GNSS networks in France and Western Europe. *Solid Earth*, 10, 1905–1920.

Mazzotti, S., Jomard, H., and Masson, F. (2020). Processes and deformation rates generating seismicity in metropolitan France and conterminous Western Europe. *BSGF—Earth Sci. Bull.*, 191. https://doi.org/10.1051/bsgf/2020019.

Poursoulis, G. et al. (2021). Archaeosphericity in France: Origins and new perspectives for cultural heritage preservation. *C. R. Géosci.* (in this issue).

Ritz, J. F. et al. (2021). Perspectives in studying active faults in metropolitan France. *C. R. Géosci.* (in this issue).

Rivera, L. et al. (2021). The historical seismogram collection in Strasbourg. *C. R. Géosci.* (in this issue).

Roger, M. (2021). Rothé's legacy to the French Central Seismological Bureau (BCSF): a history of heegemony in French seismicity. *C. R. Géosci.* (in this issue).

Schlupp, A. et al. (2021). EMS98 intensities distribution of the “Le Teil” earthquake, France, 11 November 2019 ($M_w$ 4.9) based on macroseismic surveys and field investigations. *C. R. Géosci.* (in this issue).

Schmittbuhl, J. et al. (2021). Induced and triggered seismicity below the city of Strasbourg, France from Nov 2019 to Jan 2021. *C. R. Géosci.* (in this issue).

Sira, C. et al. (2021). 1921–2021: 100 years of macroseismic studies at BCSF. *C. R. Géosci.* (in this issue).

Stocchi, A. et al. (2021). Methodology for updating magnitudes assigned to historical earthquakes: application to the La Tour-du-Pin 1889 earthquake. *C. R. Géosci.* (in this issue).

Sylvander, M. et al. (2021). Seismicity patterns in southwestern France. *C. R. Géosci.* (in this issue).