ATLAS OF MACROSEISMIC MAPS FOR FRENCH EARTHQUAKES WITH THEIR PRINCIPAL CHARACTERISTICS

The SIRENE macroseismic database has been utilized to draw isoseismal maps for the 140 best-documented French earthquakes, characterized by epicentral intensities of at least V (MSK) and located in all parts of the country. A study of focal depths derived from available local int ensity data using an intensity versus distance decay law (Sponheuer) s hows that the focal depths of most of the events considered do not exc eed about 10 km. Their distribution correlates fairly well with region al dynamic geology features. A relationship is then computed between m agnitude, intensity and focal distance, based on 73 instrumentally rec orded earthquakes (M(L) between 3.3 and 6.3) and on 217 mean radius va lues (from 2 to 380 km) for isoseismals of intensity VIII to III (MSK) . This relationship is applied to historical earthquakes contained in the database SIRENE which are characterised by their intensity only. T hese results are used in the evaluation as well deterministic as proba bilistic of the seismic hazard on the national territory.