Effects of surface topography in kinematic source inversion models. Application to the Norcia, Mw 6.5, 30 October 2016, Central Italy Earthquake.

Abstract

The topography is the only ingredient of the kinematic finite fault inversion that is explicitly known. Nevertheless, such analyses commonly assume Green's functions for a 1D layered geological model with flat surface topography. Minimization of the complexity is needed to reduce the computational cost of the inversions in realistic conditions but such assumptions can significantly impact the retrieved source parameters. In particular, the lack of management of approximations and uncertainties could lead to overconfident and biased interpretations of the kinematic results. The increasing computational power available in the coming exascale era provides the opportunity to include the topography at a high resolution and low cost. We have modified the non-negative least-square inversion method of Dreger et al. [2005] for taking into account Green’s functions generated by SPECFEM3D including explicitly significant topography. We applied this new procedure to retrieve the kinematic rupture history of the 30 October 2016 Norcia earthquake (Mw 6.5), by inverting strong motion and high-rate global positioning system datasets. The considered complex fault geometry consists of a main normal fault striking N155°, dipping 47° and belonging to the Mt. Vettore‐Mt. Bove fault system (VBFS), and a secondary fault plane striking N210° and dipping 36° to the NW. The choice is supported by seismological data, geological constraints, and observed surface breakages, but also by inferences from dynamic simulations. We have inverted for slip and rake distribution on the faults while allowing a Bayesian exploration of all the remaining parameters (i.e., rupture velocity, rise time).