Determining maximum magnitude for seismic hazard assessment in Europe (SHARE project)

Abstract

SHARE (Seismic Hazard Harmonization in Europe, http://www.share-eu.org/) is a collaborative project (2009-2012) in the FP7 EU cooperation programme aimed at providing an updated community-based seismic hazard model for the Euro-Mediterranean region. It is also one of the Regional Programmes of the Global Earthquake Model (GEM, http://www.globalquakemodel.org/) providing essential input and feedback on all hazard assessment procedures and standards in Europe. In the frame of SHARE, a specific task is devoted to the evaluation of the expected maximum magnitude (Mmax) for earthquakes in Europe. The standard Cornell-McGuire approach to probabilistic seismic hazard assessment (PSHA), in fact, requires to defining the magnitude of the largest earthquake thought to be possible within each considered source zone to avoid including unrealistically large events. Mmax is thus taken as the upper truncation magnitude of the truncated exponential (Gutenberg-Richter) frequency-magnitude distribution for each source. It is a crucial parameter in PSH studies, particularly for long return periods estimations (e.g., for designing critical facilities). We present the results of Mmax determination for the first one of the two alternative seismogenic source zone models adopted in the project: i) a classical model constituted by area source zones where seismicity is uniformly distributed and activity rates derive from earthquake catalogue only, and ii) a fault source model integrated by zones of background seismicity. For the latter, Mmax essentially derives from fault data only.