Coincident locations of rupture nucleation during the 2019 Le Teil earthquake, France and maximum stress change from local cement quarrying

Vincenzo De Novellis,Vincenzo Convertito,Riccardo Lanari,Sotiris Valkaniotis,Nicola Alessandro Pino,Francesco Casu,Mario Fernando Monterroso Tobar

doi:10.1038/s43247-020-00021-6

Abstract

Earthquake occurrence is ultimately controlled by tectonic stress load. Nevertheless, the 2019, Mw = 4.9, Le Teil earthquake in southern France occurred in an area where strain rates are relatively low. Human operations can produce increases in stress load and degradation of strength on nearby active faults, which raises the potential for failure. Here we present estimates of the rupture geometry and source directivity of the Le Teil earthquake based on differential synthetic aperture radar interferometry and seismic data. We find that almost two centuries of mass removal at a nearby cement quarry likely provided the required stress change to hasten the occurrence of the Le Teil earthquake by more than 18,000 years. We suggest that further mass removal in the area might lead to even stronger earthquakes, by activating deeper sectors of the same fault plane.

Highlights

Earthquake occurrence is controlled by tectonic stress load
Thomé-La Rouvière fault (LRf) system[11], which marks the southeastern border of the Massif Central over almost 150 km[12], in an area where intense rock extraction has been proceeding since the eighteenth century
Coseismic ground ruptures[18] (Fig. 1b) have only been detected along the northern end of LRf, close to Le Teil, where it trends about N50°

Summary

Introduction

Earthquake occurrence is controlled by tectonic stress load. the 2019, Mw = 4.9, Le Teil earthquake in southern France occurred in an area where strain rates are relatively low. We find that almost two centuries of mass removal at a nearby cement quarry likely provided the required stress change to hasten the occurrence of the Le Teil earthquake by more than 18,000 years. Large scale industrial activity might result in stress variation large enough to induce earthquakes or—added to the tectonic stress—to overcome the fault strength, advancing the time to the expected rupture. The current phase of tectonic deformation in the area, starting ~20 Ma, is characterized by NW-SE compression, coherent with the 140° direction indicated by the World Stress Map (http://www.worldstress-map.org; last accessed July 2020), and associated with a relatively low strain rate ~0.5 × 10−9 year−1 Our results indicate that the extraction activity could have triggered the Le Teil earthquake In this case, we estimate a clock advance larger than 18,000 years

Methods

Results

Conclusion