Physics-based 3D ground motion simulations of the 1703 L’Aquila earthquake: from historical reconstruction to seismic scenarios

The city of L’Aquila (central Italy) and its surrounding villages have been struck several times throughout history by strong earthquakes, most recently by the Mw 6.1 event of April 6, 2009. Previously, on February 2, 1703, L’Aquila was partially destroyed by a Mw 6.7 earthquake, which has remained in the city’s collective memory as the Grande Terremoto (“Big Earthquake”). In this paper, we present a physics-based simulation of this event, together with a set of plausible scenarios associated with the same fault structure believed to be responsible for the 1703 earthquake. Assuming the geometry of the fault plane as assigned, we simulate 120 stochastic rupture scenarios corresponding to different magnitudes, epicentral locations, and slip distributions, selected within ranges compatible with the available literature. For each scenario, several estimates of macroseismic intensity are obtained from peak ground velocity and peak ground acceleration values using a set of empirical models specifically calibrated for the Italian territory. The performance of the scenarios is then evaluated through comparison with the macroseismic intensity field provided by historical catalogues. This study demonstrates that a satisfactory reconstruction of ground shaking from major historical earthquakes can be achieved using a stochastic source model constrained by a limited amount of ex-ante information. The proposed PBS-based approach helps integrate historical catalogues, filling data gaps. However, it is affected by limitations related to near-source numerical modeling, uncertainties in the empirical correlations used to derive macroseismic intensity, and assumptions on the source geometry. Nevertheless, the generated scenarios provide valuable insights into the potential impacts of future earthquakes with characteristics similar to the investigated event.