HR: 1340h
AN: S13A-1040    [Abstracts]
TI: Mapping b-values in France using two different magnitude ranges: possible non power-law behavior
AU: Scotti, O
EM: oona.scotti@irsn.fr
AF: IRSN, BP 17, Fontenay-aux-Roses, 92262 France
AU: * Beauval, C
EM: beauval@geo.uni-potsdam.de
AF: University of Potsdam, Postfach 60 15 53 , Potsdam, 14415 Germany
AB: The first step in probabilistic seismic hazard assessment is the characterization of seismic sources. The fundamental assumption is that the Gutenberg-Richter power law can be applied and is valid at all scales. In this study, we found that the power-law model may not be verified in the southeastern regions of France. Frequency-magnitude distributions are mapped using 2 different magnitude ranges: (1) [3.0-4.4] using only homogeneous instrumental data, (2) [3.5-Mmax(observed)] using instrumental and historical data. b-values estimated on these two magnitude ranges are similar in the Pyrenees and the Rhine Basin. However, they differ significantly in the Southern Alps: the slopes estimated on magnitude range [3.0-4.4] are much steeper (b$>$1.4) than the slopes estimated on magnitudes above 3.5 (0.9$<$b$<$1.1). Until a clear identification of the underlying processes is made, a conservative option (i.e. lowest b-values) should be considered for probabilistic estimation of hazard in the eastern part of France.
DE: 7223 Seismic hazard assessment and prediction
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2004 AGU Fall Meeting