Stochastic Generator of Earthquakes for Mainland France

Corentin Gouache,François Bonneau,Pierre Tinard

doi:10.3390/app12020571

Abstract

Mainland France is characterized by low-to-moderate seismic activity, yet it is known that major earthquakes could strike this territory (e.g., Liguria in 1887 or Basel in 1356). Assessing this French seismic hazard is thus necessary in order to support building codes and to lead prevention actions towards the population. The Probabilistic Seismic Hazard Assessment (PSHA) is the classical approach used to estimate the seismic hazard. One way to apply PSHA is to generate synthetic earthquakes by propagating information from past seismicity and building various seismic scenarios. In this paper, we present an implementation of a stochastic generator of earthquakes and discuss its relevance to mimic the seismicity of low-to-moderate seismic areas. The proposed stochastic generator produces independent events (main shocks) and their correlated seismicity (only aftershocks). Main shocks are simulated first in time and magnitude considering all available data in the area, and then localized in space with the use of a probability map and regionalization. Aftershocks are simulated around main shocks by considering both the seismic moment ratio and distribution of the aftershock’s proportion. The generator is tested with mainland France data.

Highlights

Mainland France seismicity is considered as low to moderate due to its high return periods and weak maximal magnitudes
The six major earthquakes occurring after 1982 resulted in less than EUR 600 M of insured losses, representing approximately 1.5% of the total amount compensated with this compensation scheme, https://catastrophes-naturelles.ccr.fr/
CCR (Caisse Centrale de Réassurance, French insurance company) and BRGM (Bureau de Recherches Géologiques et Minières, French geological survey) have quantified the probable insurance losses associated with historical earthquakes if they occurred in the present day:

Summary

Introduction

Mainland France seismicity is considered as low to moderate due to its high return periods and weak maximal magnitudes. A few earthquakes have produced damages in this territory since the introduction of the French insurance compensation system in. The six major earthquakes occurring after 1982 resulted in less than EUR 600 M of insured losses, representing approximately 1.5% of the total amount compensated with this compensation scheme, https://catastrophes-naturelles.ccr.fr/ Major earthquakes could strike this territory (e.g., Liguria in 1887, Basel in 1356) and create financial losses and casualties. Arette (1967): EUR 120–140 M [1]; Lambesc (1909, last earthquake-related deaths): EUR 1.8–2.5 Bn [2]; Marais vendéen (1799): EUR 1.5–2.3 Bn [3]; Liguria (1887) localized in front of Nice [4]: EUR 9–13 Bn, https://catastrophesnaturelles.ccr.fr/documents/148935/368920/Bilan+Cat+Nat+1982-2020.pdf/22925938. It shows that estimating the seismic hazard and risk is necessary even in low-tomoderate seismic areas, since losses can be significant

Results

Discussion

Conclusion