Development of a 3D velocity Model for Improving the Location of Potentially Induced Earthquakes in the Gulf of Valencia

Abstract

SUMMARYOn September 2013, unusual seismic activity was detected around an underwater gas storage plant in the gulf of Valencia (Spain). According to the reports by the Spanish National Geographic Institute, more than 550 occurred during two months, the strongest having a magnitude of Mw=4.2, which took place after the gas injection activities halted. The low magnitude of the events (only 17 earthquakes had magnitudes greater than 3), their long event-to-station distance, and the inhomogeneous station distribution, made the location problem to be a great challenge. Here we present a preliminary relocation of this earthquake sequence using absolute and relative methods. We also present a new 3D shear-wave velocity model estimated from inversion of Ambient Noise Tomography data which will serve to obtain more accurate seismic-wave travel times to improve the earthquakes location in this area. The interpretation of the results in terms of the tectonic structure of the region is in progress.