Monitoring Seismotectonic Activity in the Surroundings of the Vuache Fault

Monitoring seismotectonic activity in the surroundings of the Vuache fault

Dr. N. Houlié 1 and Dr. J. Fréchet 2 1 Nicolas Houlie Geologie GmbH, Zurich, CH 2 JFrechet Consulting, Grenoble, FR

Introduction

The new CERN measurement facility will be more accurate than ever. Like all high-precision instrument, it will be more sensitive to its environment than its predecessor and a wider range of signals resulting from natural or human-driven processes should be considered as noise sources. For instance, the next generation of instruments deployed by CERN will be the first to be disturbed by external processes such as Swiss tectonics and the first effect of climate change on the hydrogeology systems. Fortunately, small amplitudes disturbances of various frequencies have been documented from a wide range of past activities such as seismology, geodesy and space programs. Even though processes are well known by CERN teams, external expertise will be required to characterize the external noise contribution from outside the CERN facilities in both a local and a regional context.

Noise contributors

New noise contributors are diverse in terms of amplitudes and of durations and periodicity:

• Seismic activity (natural or in response to CERN activities or to the geothermal development)

• Meteorological effect (troposphere, drying and recharge of natural water reservoirs)

• Anthropic activities (trains, planes landing, roadwork, excavations, etc.) • Long-term tectonics (lithosphere deformation, long-term response to earthquakes)

• Landslides

We show in Figure 1 the variability of the disturbances parameters (Psimoulis et al. 2018).

Figure 1: Amplitude versus duration diagram for various geological catastrophic processes. We show detection limits for GPS, dynamic GPS and microgravimetry. In this study, as in any real- time algorithm, we focus on detecting small amplitudes as fast as possible. dynGPS curves are from analyses of dynamic GPS time-series recorded during seismic wave propagations. Static GPS is able to detect motion larger than 1 cm for duration larger than 104 s. From Psimoulis, Houlié et al., GJI, 2019.

Proposed work

We propose an appropriate monitoring of the Vuache fault which is to our knowledge the best candidate for the generation of seismic and aseismic activity in the area. This monitoring will include: 1. Review of the historical and instrumental seismicity (moment tensors, first motion focal mechanisms, and microseismicity)

2. Installation of supplementary seismic stations (short-period velocity sensors). 3. Characterization of the seismic activity in the area of the Vuache.

4. Characterization of the local surface deformation (triangulation, grids, etc.) using GPS and InSAR. Re-processing of the strain rate field

5. Identification of the most active seismic segments in the area.

Beyond the permitting of the stations, there is no bottleneck in this proposal. Drs. Fréchet and Houlié are very experienced in field deployment in France (and abroad), in data processing and reporting.

Figure 2: Map of provisory envisaged seismic (red triangles) and GPS networks (blue squares). Existing seismic and GPS are shown using grey symbols.

Planning (Gantt chart)

The first priority of the project will be to deploy the seismic and the geodetic networks (Figure 2). The exact location of stations will be reevaluated during implementation of the network. From the data gathered various analyses will be carried following approaches previously published in peer-reviewed publications (Fréchet et al., 1989; Houlié et al., 2018; Psimoulis et al., 2018).

Reporting will be delivered on a yearly basis and bibliography continuously searched.

Y1 Y2 Y3 Y4 Y5 Bibliography Continuous

Networks deployment Seismic activity monitoring Surface deformation Most active segment Reporting

Deliverables

• To Be Defined with CERN (seismicity catalogue, surface vector field, etc.)

Bibliography

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J. Fréchet: Poupinet, G., Ellsworth, W. L., Fréchet, J., 1984. Monitoring velocity variations in the crust using earthquake doublets: an application to the Calaveras fault, California. J. Geophys. Res., 89, 7, 5719-5731. Fréchet, J., Martel, L., Nikolla, L., Poupinet, G., 1989. Application of the cross-spectral moving- window technique (CSMWT) to the seismic monitoring of forced fluid migration in a rock mass. Int. J. Rock Mech. & Min. Sc. & Geomech. Abstr. 26, 221-233. Fréchet, J., Thouvenot, F., Jenatton, L., Hoang-Trong, P., Frogneux, M., 1996. Le séisme du Grand-Bornand (Haute-Savoie) du 14 décembre 1994 : un coulissage dextre dans le socle subalpin. C. R. Acad. Sci. Paris, 323, II, 6, 517-524. Thouvenot, F., Fréchet, J., Tapponnier, P., Thomas, J.-C., Le Brun, B., Ménard, G., Lacassin, R., Jenatton, L., Grasso, J.-R., Coutant, O., Paul, A., Hatzfeld, D., 1998. The ML 5.3 Épagny (French Alps) earthquake of 1996 July 15: a long-awaited event on the Vuache fault. Geophys. J. Int., 135, 3, 876-892. Fréchet, J., Thouvenot, F., Frogneux, M., Deichmann, N., Cara, M., 2011. The MW 4.5 Vallorcine (French Alps) earthquake of 8 September 2005 and its complex aftershock sequence. J. Seismology, 15, 1, 43-58. Fréchet, J., Meghraoui, M., Stucchi M. (eds.), 2008. Historical Seismology: Interdisciplinary Studies of Past and Recent Earthquakes. Series: Modern Approaches in Solid Earth Sciences, v.2, Springer, 446 pp.

Western Alps: Billant, J., 2016. Caractérisation de la déformation tectonique récente du système de failles de Belledonne et de l'avant pays alpin (vallée du Rhône). Thèse de doctorat, Sciences de l'environnement, Univ. Aix-Marseille. De la Taille, C., 2015. Évaluation de l’activité tectonique quaternaire des failles du Jura Méridional (France). Thèse de doctorat, Univ. Grenoble Alpes, 247 pp.

Vuache Fault: Amato, E., 1988. La faille du Vuache (Jura méridional) : un accident géologique pas si tranquille. Le Globe - Revue genevoise de géographie, 128, 39-61 Baize, S., Cushing, M., Lemeille, F., Revil, A., Bolève, A., Leroy, P., Nicoud, G., 2006. La faille du Vuache, un décrochement sénestre actif. Réunion Sciences de la Terre (RST), Session "Aléas Naturels", 4-8 Décembre 2006, Paris, France. Baize, S., Lemeille, F., Cushing, M., Schwenninger, J.-L., Nicoud, G., 2009. Multidisciplinary approach to the study of the Vuache fault (France) – Part I: Geological characterization of the fault. Intern. Conf. Provence 2009, Aix-en-Provence. Baize, S., Cushing, M., Lemeille, F., Gélis, C., Texier, D., Nicoud, G., Schwenninger, J.-L., 2011. Contribution to the seismic hazard assessment of a slow active fault, the Vuache fault in the southern Molasse basin (France). Bulletin de la Société géologique de France, 182, 4. Bordon, J., Charollais, J., 2009. Le Vuache, montagne insolite... I.P.C.V. Mairie, Vulbens, 2009, 70 pp. Charollais, J., et al., 2013. Présentation d'une nouvelle carte géologique du Vuache et du Mont de Musièges. Arch. Sci., 66, 1-64. De L'Harpe, A., 1996. La faille du Vuache et ses conséquences : étude du séisme du 15 juillet 1996. Le Globe, Revue genevoise de géographie, 136, 85-94. Gélis, C., Baize, S., Texier, S., 2009. Multidisciplinary approach to the study of the Vuache fault (France) – Part II: Paleoseismological investigations. Intern. Conf. Provence 2009, Aix-en-Provence. Mastrangelo, B., Charollais, J., 2018. Nouvelle conception de la structure du Salève. Arch. Sci., 70, 43-50.