Testing the stability of moment tensor solutions for small earthquakes in the Calabro-Peloritan arc region (southern Italy)

The aim of this study is to test the stability of moment tensor solutions for crustal earthquakes in the Calabro-Peloritan area (Southern Italy). We used waveforms recorded by the Italian National Seismic Network managed by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the CAT-SCAN (Calabria Apennine Tyrrhenian - Subduction Collision Accretion Network) project. We computed the moment tensor solutions using the Cut And Paste (CAP) method. The technique allows the determination of the source depth, moment magnitude and focal mechanisms using a grid search technique. For the earthquakes investigated, we tried different station distributions and different velocity models. Results were also checked by computing the moment tensor solutions using the SLUMT grid-search method. Both methods (CAP and SLUMT) allow time shifts between synthetic and observed data in order to reduce the dependence of the solution on the assumed velocity model and on earthquake location errors. Comparisons have been made with the available published solutions. The final focal mechanisms were robustly determined. We show that the application of the CAP and SLUMT methods can provide good-quality solutions in a magnitude range not properly represented in the Italian national earthquake catalogues, and where the solutions estimated from P-onset polarities are often poorly constrained.