Coupling at the Northern Chile seismic gap and moment balance after the Mw=8.2 Pisagua event 2014

Abstract:

The Mw=8.1 Pisagua earthquake on April 1st, 2014, was the first large event occurring in the Northern Chile seismic gap since the Mw=8.8 event in 1877. This region has been monitored extensively with a variety of sensors in the framework of the integrated plate boundary observatory (IPOC). Here, we use pre-seismic GNSS observations to infer the coupling at the subduction plate interface. We carefully analyze the robustness of the results by testing various boundary conditions, rake angle constraints, regularization schemes and Earth models. A slip distribution is inverted from coseismic observations and compared to the locking pattern. Assuming temporally stable coupling, we compute accumulated moment and subtract all major seismic events since 1877, including the Pisagua event. We conclude that this event released some of the accumulated moment in the central region of the seismic gap, but significantly more could still be present.