Coseismic slip distribution along a curved rupture embedded in the 3D heterogeneous crust: Joint inversion of InSAR and GPS data for the 2016 Central Italy earthquake

The epicenter of the 2016 Central Italy earthquake struck the mountainous Central Appennines within an accretionary prism of the subduction boundary between the Eurasian Plate and Adria Microplate. Field evidence documents extensive listric faults connected to decollements at various depths near the epicentral area, which is also inferred by the aftershock sequences between 9 and 11 km and consistent with the rupture kinematic of the nearby 2009 Mw6.3 L'Aquila earthquake. The in-situ complex geology and structural configurations require deformation models that are capable of accounting for both the listric curvature of the rupture and the surrounding heterogeneous rock properties of the plate boundary. Based on the inverse analysis of available ALOS-2 interferograms and GPS data, we found that a planar fault configuration cannot readily explain the focal mechanism as well as the nearfield deformation signature. Here, we adopt 3D finite element models (FEMs) to simulate a realistic tectonic environment of Central Mediterranean by simulating slip along a curved fault embedded in a domain having distributed rock materials from CRUST2.0 and surface topography. Innovative nonlinear analysis optimizes the earthquake fault curvature and location within crustal heterogeneity, involving more than randomly perturbed 3840 FEMs. A distributed slip model is derived for this optimized fault geometry and provides significantly better prediction than a customary planar rupture. These results highlight the necessity of next-generation earthquake deformational models in the context of earthquake hazard assessments, particularly for complex geological environments such as accretionary prisms and orogenic belts.