Coda Attenuation Analysis in the West Bohemia/Vogtland Earthquake Swarm Area

摘要

Seismic coda represents a valuable source of information about the attenuation of the high-frequency waves in the studied region. The quality factor Q derived from coda is an integral parameter of the volume surrounding the hypocenter and seismic station and, according to the applied method, represents the total attenuation or the intrinsic and scattering parts. We analyzed records of 13 selected earthquakes in the magnitude range 1.7-2.9 of the 2011 swarm from West Bohemian/Vogtland area (central Europe), which were recorded at epicentral distances from 7 to 50 km. Two methods were applied: coda method for estimation of the Q (c) and the Multiple Lapse Time Windows Analysis for separation of the scattering and intrinsic loss by estimation of Q (i) and Q (sc). Careful selection of the analyzed events was necessary due to the frequent contamination of coda decays by the running seismic swarm activity. The resulting coda Q (c) is relatively high with respect to the geodynamic activity and varies between 100 and 2500 within the analyzed frequency range of 1-18 Hz. The intrinsic loss dominates over scattering attenuation with Q (i) increasing from 100 and 1850 and Q (sc) from 300 to 3400 in the same frequency range, which is consistent with the geodynamic activity of the region. We find that the intrinsic attenuation in West-Bohemia/Vogtland is higher that in neighboring Germany, which could be attributed to the heterogeneity of the crust in central Europe.