Focal Mechanism and Tectonic Stress Field of Small Earthquakes in Southwest Margin of Dongting Basin

Abstract

Based on the broadband seismic waveform data recorded by Hunan digital seismic network, 41 focal mechanism solutions of small earthquakes with M L ≥1.8 in the southwest margin of Dongting Basin from 2009 to 2017 were obtained by integrating the P-wave first-motion and maximum amplitude ratio methods. The parameters of focal mechanism solutions were analyzed using mathematical statistics and systematic cluster analysis. The results showed that the seismic properties in this area are mainly thrust type ( 30/41 ), and the principal compressive stress axis in the focal mechanism solution parameters is NNW and NE, while the tensile stress axis is SSW. Compared to previous studies, the inversion results of the focal mechanism of small earthquakes in the southwest margin of Dongting Basin are in good agreement with the focal mechanism solutions of regional historical strong earthquakes, indicating that the focal mechanism solutions of small earthquakes can represent the regional tectonic stress field in this area.