Integrating structural and seismotectonic data in a fault catalog for Seismic Hazard Assessment for South East France

Identifying and studying active faults is crucial for assessing seismic hazards and implementing measures to mitigate earthquake risks in areas prone to seismic activity. The region of SE France is found in a continental active tectonic domain where seismic activity is low to moderate and crustal deformation is slow, nevertheless about 1 magnitude 5 earthquake is recorded every 5 years and 1 magnitude 6 per century (estimated from the historical seismic catalog EPICA). Social vulnerability to seismic hazard in SE France is noticeble due to the presence of urban agglomerations, chemical industries and nuclear facilities.

Today’s seismic activity in this region is contrasted between the core of the Alps, where most of the activity is concentrated in transtensional behaviour, and the Alpine foreland, where activity is low and transpressional. The related geodynamics are dominated by the interaction of far-field plate tectonics and buoyancy forces. However, seismic hazard assessments for the region are challenging due to the relatively small time windows of seismic records (~ 100 years of instrumental period, ~ 1000 years of historical period) with respect to the small deformation rates as shown by 25 years of GNSS data acquisition. The 4.9 Mw Teil earthquake in 2019 illustrates the importance of characterising faults and their potential activity. This is a challenging task for this region as its structure is complex and derives from several tectonic phases. Moreover, the definition of active fault is still under debate and is here discussed.

This study aims to build an analytical and critical compilation of fault data, including geological maps, previous fault datasets, fault models, neotectonic evidences, seismic catalogs and seismotectonic analysis. To determine the uncertainties of the compiled data we propose a methodology of estimation of activity, importance and reliability for each fault. The resulting SEFPAF fault dataset (South East France Potentially Active Faults) will then be applied to build fault models and earthquake occurrence models, with a final goal of assessing probabilistic seismic hazard for South East France.