Stress evolution during the April 2009 L’Aquila Seismic sequence (central Italy)

The 6th of April 2009 MW 6.3 earthquake that struk the historical city of L’Aquila (central Italy) caused a huge impact to the society and nearly 300 casualties. The main shock has been preceeded by a foreshock sequence started few months before and culminated with a ML 4.0 on March 30. The aftershocks mainly located within the first 12 km of depth are distributed over an area almost 50 km long NW-trending. The main shock and most of the aftershocks are associated with normal faulting mechanisms with a minor left-lateral strike slip component. Seismicity migrated to the north on a sub-parallel normal fault forming a dextral en-enchelon fault system. In this study we compute the coseismic stress changes caused by the largest magnitude shocks of the sequence in an elastic half space, and we adopt both a homogeneous and a layered crustal structure. The slip on the main shock fault plane is heterogeneous and it has been imaged by inverting DinSar and GPS measurements. The goal of this study is to model fault interaction through coseismic stress perturabtions and to investigate stress triggering of mainshocks and aftershocks by resolving stress changes onto the available fault plane solutions and using constraints from local tectonics and structural geology. Our preliminary results show that the large majority of the events with Mw>4.5 nucleate in areas of enhanced Coulomb stress. We aim to model also the migration of the seismicity towards the north western volume of the fault system started about two month after the occurrence of the main event. In doing this we also investigate the contribution of fluid flow and pore pressure relaxation.