High-precision relocation of seismic sequences above a dipping Moho: the case of the January–February 2014 seismic sequence on Cephalonia island (Greece)

摘要

Detailed velocity structure and Moho mapping is of crucial importance for ahigh precision relocation of seismicity occurring out of, or marginal to,the geometry of seismological networks. Usually the seismographic networks donot cover the boundaries of converging plates such as the Hellenic arc. Thecrustal thinning from the plate boundary towards the back-arc area createssignificant errors in accurately locating the earthquake, especially whendistant seismic phases are included in the analysis. The case of theCephalonia (Ionian Sea, Greece) sequence of January–February 2014 providedan excellent example where the hypocentral precision was greatly affected bythe crustal thinning from the plate boundary at the Ionian sea towards theAegean sea. This effect was examined in detail by testing various velocitymodels of the region in order to determine an optimal model. Our testsresulted in the adoption of a velocity model that resembles the crustalthinning of the region. Then, a relocation procedure was performed in theCephalonia sequence for the time period of 26 January to 15 May 2014 byapplying probabilistic non-linear location algorithms. The high-precisionrelocation resulted in an improved spatial distribution of the seismicitywith respect to the preliminary locations and provided a reliable basis toexamine seismotectonic implications of the Cephalonia sequence.