What can we learn from the January 2012 northern Italy earthquakes?

This note focuses on the ground motion recorded during the recent moderate earthquakes that occurred in the central part of northern Italy (Panel 1), a region that is characterized by low seismicity. For this area, the Italian seismic hazard map [Stucchi et al. 2011] assigns a maximum horizontal acceleration (rock site) of up to 0.2 g (10% probability of being exceeded in 50 yr). In the last 4 yr, this region has been struck by 9 earthquakes in the magnitude range 4 ≤Mw ≤ 5.0, with the three largest located in the Northern Apennines (the Mw 4.9 and 5.0 Parma events, in December 2008 and January 2012) and on the Po Plain (the Mw 4.9 Reggio Emila event, in January 2012). We have analyzed the strong-motion data (distance <300 km) from these events as recorded by stations belonging to the Istituto Nazionale di Geofisica e Vulcanologia (RAIS, http://rais.mi.ingv.it; RSNC, http://iside.rm.ingv.it) and the Department of Civil Protection (RAN, www.protezionecivile.it; http://itaca.mi.ingv.it). […]