Gutenberg-Richter Law Parameters Analysis Using the Hellenic Unified Seismic Network Data Through FastBee Technique

Abstract

The mapping of the minimum completeness magnitude Mc and parameters (a-and b-value) of the Guttenberg-Richter (G-R) law was studied for Greece territory and adjacent areas by using the new earthquakes catalog produced by the Hellenic Unified Seismological Network (HUSN). For the calculation of the parameters a-and b-values the visual method of the completeness magnitude (Mc) definition was used by means of FastBee technique. The results show that with the commissioning of the new network HUSN, the Mc have significantly decreased and have achieved the value M=1.5 in the central part of Greece and practically up to M=2.0 for the entire territory. Despite the short time of observation (11.2011-05.2014) the statistical reliable pattern of the spatial distribution of the G-R law parameters for territory of Greece was derived. In generally the spatial distributions of a-and b-value reflect the known seismotectonic structures of Greece. The distribution of the relatively low b-value coincides with the tectonic compression field which acts along the Hellenic Trench. The relatively low b-value is also observed on the northern-eastern part of Greece. The relatively high values of b-value meet mainly in the central Greece, where the extensional stress field dominates. The spatial pattern of the parameter a-value is reflecting the seismic activity of the under study region. The results of detailed analysis of b-value distribution with depth in the Corinthian Gulf area show that its values significantly decreased (from 1.6 to 0.76) in depth interval from 1 up to 17 km and then gradually increased up to 30 km. The pattern of b-value in depth distribution in this region was interpreted in the frame of hypothesis about the brittle-ductile transition zone existence. On the basis of this result, it is supposed that detailed study of the b-value distribution versus depth can be used for assessment of the focal depths of the impending strong earthquake. The present results show the applicability and the efficiency of the FastBEE technique for three dimension mapping of Mc and the G-R parameters.