The high-frequency magnitude (m3Hz) of Italian earthquakes from intensity data – the ICEM Catalog

The assessment of seismic hazard and risk requires a catalogue of earthquakes (both historical and recorded during the instrumental era), where the location and magnitude of events affecting the study area are reported. Mw is commonly used for this aim, but it is a static measure of earthquake size and it cannot capture the full extent of earthquake source complexity. Other magnitude scales connected to the rupture kinematics and dynamics should complement Mw in hazard studies, but this required efforts in re-analyzing catalogs of intensity data. To this aim, we developed a high-frequency magnitude (m3Hz) estimated using a random or log-averaged horizontal component of ground motion from frequencies above the highest corner frequency of the earthquake source spectrum. Here, we apply the novel procedure to the intensity data from the Parametric Catalogue of Italian Earthquakes (CPTI15). We derive m3Hz for 1,951 earthquakes (from 1117 to 2020). The new earthquake catalog is defined by the acronym ICEM. For all earthquakes a quality index based on the variance-to-mean ratio (VMR) has been assigned.