Revised Catalogue of Moment Tensors of 2016-2017 Central Italy Seismic Sequence and Uncertainty for Source Parameters of Mainshocks

The Central Italy seismic sequence that began on 24 August 2016 has been marked by three mainshocks in two months culminated with the 30th October 2016 M_w 6.5 event. Location, depth and prevalent normal faulting mechanisms indicate that the sequence originated in the shallow crust of the Apennine chain where the current extensional regime overprints contractional structures. Structural complexity plays a major role in fault segmentation and interaction in this region, with important consequences on seismic behavior and mechanics of earthquake faulting. This complexity is evidenced by the co-existence of fault planes with different focal mechanisms in the same area.

In this study we investigate the stability of the moment tensor solution for the three mainshocks of the sequence by studying the effect of the number and distribution of the considered stations and of the employed wave speed model (1D and 3D) with the goal of providing more reliable estimates of the source parameters (strike, dip, rake and M_w) and corresponding uncertainties. Performing the bootstrap analysis on hundreds of solutions that will be computed by varying number and distribution of stations and 1D and 3D velocity models, will allow us to estimate the uncertainty of the moment tensor solutions due to the station selection procedure and the approximated sampling of the Earth.

We will also report on source geometries of the Central Italy sequence as retrieved by moment tensor analysis by integrating the actual TDMT revised catalogue (http://cnt.rm.ingv.it/tdmt) with new updated solutions also based on a new Italian 3D wave speed model.

We believe that the estimate of uncertainties associated to the computed focal planes and the obtained M_w for the three mainshocks as well as the realization of a complete moment tensor catalogue will contribute to explain the complexity of the seismogenic processes active in the Central Apennines and help in understanding the main features of this seismic sequence.