Recalibration of the distance correction term for local magnitude (ML) computations in Italy

Abstract

Even though the most reliable and physically consistent defi- nition of the size of an earthquake is the moment magnitude Mw, small earthquakes located in Italy and in other regions of the world are traditionally calculated using local magnitude ML. Because such magnitude was calibrated using a set of southern California earthquakes, a specific recalibration is required in regions with different attenuation properties. We determine the amplitude attenuation function for Italy using various datasets and different functional forms. We also esti- mate separate attenuation equations for a subdivision of the Italian area in two regions with different crustal properties.