Deep Structural Features of the Sanhe–Pinggu Strong Earthquake Area Imaged by Wide Angle Reflection / Refraction and Deep Seismic Reflection Profiling

Abstract

AbstractIn this paper, the data from deep seismic reflection and wide angle reflection profiling completed in Sanhe‐Pinggu strong earthquake (M=8.0) region are comprehensively studied and interpreted. The result shows that the layered crustal structures obtained by the two investigation methods are basically consistent. In Sanhe‐Pinggu strong earthquake region, the fluctuation of basement structures is considerable, shallow faults well developed, and the thickness of upper crust and the depth of Moho discontinuity are 21–23km and 36–37km, respectively. Among several faults determined by this study, the Xiadian fault is a tectonic zone with obvious characteristic and coexistence of both shallow and deep faults. Surrounding the focus, anomalous velocity structures and complex geological tectonic environment mean that these positions are favorable for strong earthquake developing and occurring. The phenomena of Moho discontinuity fluctuation and rather thick overlapping reflection layers and existence of locally complex cuneiform reflection zones indicate that the strong compression and deformation of the crustal structures had taken place in this region, and these phenomena also reflect that magmatic activity put strong reformation on material and structures in lower crust to result in complicated deep crustal structures in the region which may be considered as deep background for the development and occurrence of Sanhe‐Pinggu strong earthquake (M=8.0).