Repetitive small seismicity coupled with rainfall can trigger large slope instabilities on metastable volcanic edifices

Virginie Durand (1) , Anne Mangeney (2, 3) , Pascal Bernard (2, 3) , Xiaoping Jia (4) , Fabian Bonilla (5, 6) , Claudio Satriano (5) , Jean-Marie Saurel (2, 3) , El Madani Aissaoui (2, 3) , Aline Peltier (2, 3) , Valérie Ferrazzini (2, 3) , Philippe Kowalski (2, 3) , Frédéric Lauret (2, 3) , Christophe Brunet (2, 3) , Clément Hibert (7, 8)

1 GEOAZUR 7329 - Géoazur
2 IPG Paris - Institut de Physique du Globe de Paris
3 OVPF - Observatoire Volcanologique du Piton de la Fournaise
4 IL - Institut Langevin - Ondes et Images (UMR7587)
5 IPGP (UMR_7154) - Institut de Physique du Globe de Paris
6 GERS-SRO - Sols, Roches et Ouvrages Géotechniques
7 ITES - Institut Terre Environnement Strasbourg
8 EOST - Ecole et Observatoire des Sciences de la Terre

Quantifying the effect of external forcings like seismicity or rain on slope destabilization is a long-standing and challenging issue. To investigate the respective roles of these forcings, we analyze an unprecedented 10-year long catalog of rockfalls occurring in the crater of the Piton de la Fournaise volcano (La Reunion Island), using statistical tools originally developed for earthquakes. Our analysis reveals the predominant effect of low amplitude repetitive seismicity in the triggering of rockfalls located at a few kilometers from the source, due to progressive damaging of the slope. Moreover, we show that the efficiency and time-delay of this dynamic triggering is controlled by the stability state of the slope, i.e. its closeness to the failure, as observed with lab-experiments on metastable granular slopes. Our results show the need to account for long-term swarm-type seismic activity that can affect the stability of geological structures like slopes and faults, but also buildings.

Domaines: Géophysique [physics.geo-ph]

Virginie Durand, Anne Mangeney, Pascal Bernard, Xiaoping Jia, Fabian Bonilla, et al.. Repetitive small seismicity coupled with rainfall can trigger large slope instabilities on metastable volcanic edifices. Communications Earth & Environment, 2023, 4, ⟨10.1038/s43247-023-00996-y⟩. ⟨hal-04401982⟩