Coda Q in the Geophysical Environment of the Northeast Caucasus

Abstract

For the eastern zone of the North Caucasus, including the Terek–Caspian trough, Dagestan wedge, and adjacent structures, with the maximum coverage of the data from the Federal network of seismological observations of the Geophysical Survey of the Russian Academy of Sciences (GS RAS), the regional frequency-dependent relations are determined using the Coda Wave Decay (CWD) method to estimate the seismic Q-factor of the Earth’s crust and upper mantle. In total, waveforms from 394 crustal earthquakes with source depths from 1 to 42 km and magnitudes М from 2.2 to 5.5 are analyzed using the Coda Q module of the SEISAN software package (Havskov et al., 2020). The seismic Q estimation technique using the single-scattering model is described in detail. Recommendations are given how to practically use the obtained estimates characterizing the wave properties of different-scale volumes of the fault-block geological environment to make attenuation corrections when calculating the source spectral parameters in the eastern zone of the North Caucasus. The results of the study will help to augment the information content of earthquake catalogs, in particular, with the data on energy characteristics of seismic events (universal moment magnitude values M_w) in the most seismically active regions of the Russian Federation.