Fault population recognition through microseismicity in Mygdonia region (northern Greece)

Seismicity in the area of Mygdonia basin (northern Greece) is lately characterized by a lack of strong events (M≥5.0) on the seismogenic faults known to have been repeatedly activated in the past. Only small to moderate magnitude earthquakes (M≤4.8) have occurred since 2000 in the area. Therefore, microseismicity is the only available information to be exploited for the identification of active faults and hazard assessment, since it may occur everywhere, as well as onto the major hazardous faults. Earthquakes recorded between 2000 and 2014 by the Hellenic Seismological Network were relocated by using the available P- and S-seismic wave arrivals in order to improve location accuracy. The V_P/V_S velocity ratio which was found equal to 1.78, along with station time delays, were all included in the Hypoinverse computer program. In the case of strong spatial or temporal clustering the HypoDD algorithm was employed for further improving location accuracy. The relocated seismicity was used to outline the geometrical properties of the local fault population and identify seismogenic faults deprived of a clear surface expression. Cross-sections made perpendicular to the main axis of the seismicity alignments, shed more light to the local fault network.