Moment tensor resolvability for the Irpinia Seismic Network, Southern Italy

We present an analysis of the resolution of focal mechanisms obtained through moment tensor inversion. Our analysis is based on the method proposed by Zahradnik and Custodio (2012), which relies on the linear inverse theory to build an error ellipsoid, and then uses a grid search approach to determine the family of acceptable solutions inside the ellipsoid. We focus our attention on data recorded at the Irpinia Seismic Network which is a high dynamic-range, dense, seismographic network that has been deployed in Southern Italy, along the Campania-Lucania Apennines where large historical earthquakes occurred in the past. The network has also been designed to be the backbone infrastructure for a regional earthquake early-warning system. Some preliminary studies show that the pattern of focal mechanism resolution mainly depends on two variables that are the source radiation pattern and the station geometry. In particular, station geometry is the dominant factor when relative data error is low, while radiation pattern dominates the resolution maps when relative data error is high. We also present moment tensor inversions with uncertainty assessment for four regional Italian earthquakes which have been well recorded at the network: Mw 6.4, 2009 L'Aquila earthquake; Mw 4.3, 2010 Foggia earthquake; Mw 4.2, 2012 Benevento earthquake; and Mw5.1, 2012 Pollino earthquake. The successful analysis on these earthquakes is particularly noteworthy given that they were recorded at large source-station distances (up to about 280 km) and with large azimuthal gaps (larger than 319°).