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

摘要

The source parameters and scaling properties for two seismic areas (Vrancioaia and Ramnicu Sarat) of the Carpathians Mountains foredeep, adjacent to the Vrancea seismic region, are analyzed by standard time and frequency domain methods and empirical Green's function deconvolution. The study area is characterized by distinct shallow seismicity clusters with small and moderate-size earthquakes (M < 5). The digital short-period and broad-band waveforms recorded by the Romanian seismic network are considered. The analysis of the retrieved source parameters possibly outlines a heterogeneous faulting process. A significant difference in the stress drop value is emphasized between Vrancioaia and Ramnicu Skat earthquakes, which is assumed to be ascribed to differences in the local seismotectonics and reology. Our paper shows the efficiency of the empirical Green's function deconvolution in eliminating the instrument, path and site effects for the earthquake sequences in the Ramnicu Skat region. The apparent source time function is generally well constrained, as demonstrated by our tests using in parallel both, appropriate Green's functions of different sizes, and instruments with different frequency bandwidth. (C) 2001 Elsevier Science B.V. All rights reserved. [References: 26]