Instrumental Seismicity of the Western Alps: A Revised Catalogue

The western Alpine regions have been instrumented since the beginning of the century, and the number of seismological stations largely increased since 1980. This dense network has allowed an important improvement in the hypocentral determination, even for low magnitude events. This condition was a good opportunity to perform a synthesis of 32 years of instrumental seismicity in the Western Alps and southeast of France (1962–1993) and to attempt an improvement of the older event location with the assistance of the more recent locations. The revised catalogue of seismicity is built using station corrections and regional crustal models. After the elimination of non-natural events, the catalogue is composed of 6697 events. Another improvement corresponds to the revision of magnitudes. We performed several tests to evaluate the reliability of our results: location of quarry events and rock bursts, epicentral correlation with geological features, coherence in depth with interpreted seismic profile (ECORS line), Moho isobaths. A first use of this catalogue is presented for the Haute-Ubaye region in the southwestern Alps.