The impact of geology on the nucleation of 2009 L'Aquila earthquake via 3D numerical optimization model of ground deformation pattern

To investigate the impact of the deep fault geometry and tectonic setting on the co-seismic ground deformation pattern of April 6, 2009 L'Aquila earthquake (Mw 6.3, Central Italy), we include the 3D structural-geological model, built for the study area, in a Finite Element Environment. To this purpose, we model the evolution of the failure processes in a structural mechanical context, under the plane stress approximation. We assume the linear elastic behavior of the involved materials and evolve our numerical model through two stages: (i) compacting under the weight of the rock successions (gravity loading), the deformation model reaches a stable equilibrium; (ii) the co-seismic stage simulates, through a distributed slip along the active fault, the released stresses. In the second step, in order to individuate the seismogenic fault, we analyze the spatial distribution of the fore- and aftershocks in the considered area. In the optimization procedure, based on the genetic algorithm, we exploit the DInSAR deformation velocity maps retrieved by ENVISAT (ascending and descending orbits) and COSMO-SkyMed data (ascending orbit) to constrain the numerical solution; more specifically, we first generate several forward mechanical models, then, we compare these with the recorded ground deformation fields, in order to select the best boundaries setting. Finally, the performed multi-parametric 3D numeric model allow us to quantify the stress-drop associated to the L'Aquila seismic event.