Source characteristics of the seismic sequences in the Eastern Carpathiansforedeep region (Romania)

The source parameters and scaling properties for two seismic areas (Vrancio aia and Ramnicu Sarat) of the Carpathians Mountains foredeep, adjacent to t he Vrancea seismic region, are analyzed by standard time and frequency doma in methods and empirical Green's function deconvolution. The study area is characterized by distinct shallow seismicity clusters with small and modera te-size earthquakes (M < 5). The digital short-period and broad-band wavefo rms recorded by the Romanian seismic network are considered. The analysis o f the retrieved source parameters possibly outlines a heterogeneous faultin g process. A significant difference in the stress drop value is emphasized between Vrancioaia and Ramnicu Skat earthquakes, which is assumed to be asc ribed to differences in the local seismotectonics and reology. Our paper sh ows the efficiency of the empirical Green's function deconvolution in elimi nating the instrument, path and site effects for the earthquake sequences i n the Ramnicu Skat region. The apparent source time function is generally w ell constrained, as demonstrated by our tests using in parallel both, appro priate Green's functions of different sizes, and instruments with different frequency bandwidth. (C) 2001 Elsevier Science B.V. All rights reserved.