The Spatiotemporal Analysis of the Minimum Magnitude of Completeness Mc and the Gutenberg–Richter Law bValue Parameter using the Earthquake Catalog of Greeceстатья
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Аннотация:Spatiotemporal mapping the minimum magnitude of completeness Mc and bvalue of the Guten berg–Richter law is conducted for the earthquake catalog data of Greece. The data were recorded by the seis mic network of the Institute of Geodynamics of the National Observatory of Athens (GINOA) in 1970–2010 and by the Hellenic Unified Seismic Network (HUSN) in 2011–2014. It is shown that with the beginning of the measurements at HUSN, the number of the recorded events more than quintupled. The magnitude of completeness Mc of the earthquake catalog for 1970–2010 varies within 2.7 to 3.5, whereas starting from April 2011 it decreases to 1.5–1.8 in the central part of the region and fluctuates around the average of 2.0 in the study region overall. The magnitude of completeness Mc and bvalue for the catalogs of the earthquakes recorded by the old (GINOA) and new (HUSN) seismic networks are compared. It is hypothesized that the magnitude of completeness Mc may affect the bvalue estimates. The spatial distribution of the bvalue deter mined from the HUSN catalog data generally agrees with the main geotectonic features of the studied terri tory. It is shown that the bvalue is below 1 in the zones of compression and is larger than or equal to 1 in the zones dominated by extension. The established depth dependence of the bvalue is pretty much consistent with the hypothesis of a brittle–ductile transition zone existing in the Earth’s crust. It is assumed that the source depth of a strong earthquake can probably be estimated from the depth distribution of the bvalue, which can be used for seismic hazard assessment.