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

Abstract

In 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).

2‐D Crustal Structures Along Wuqing‐Beijing‐Chicheng Deep Seismic Sounding Profile

“…The general variational trend of the Moho in study region is deepening gradually from Wuqing to Chicheng. The Moho presents a slope from Beijing to stake number 300 km, and its depth is 34 km under Beijing, 36.0 km under near stake number 285 km, and 39.0 km under near stake number 300 km, which are consistent with other results [6,7] . The variation of Moho reaches 5.0 km within a range of about 20 km in the transitional belt between Yanshan mountain fold belt and North China plain.…”

Intrinsically Safe in the Tunnel Construction under Complex Geological Conditions

“…And identify the major kinds of the geological disasters in different segments and the controlling geological factors. As the basis for the choice of the means of geological advanced forecasting technology, the layout of the forecasting project, the analysis of the forecasting results [4]. The feedback information of Geological advanced forecasting techniques can effectively control the risks from the sources.…”

Late Quaternary activity of the Xiadian west concealed fault east to Beijing and its tectonic significance

“…Many researchers have studied the Xiadian fault zone with different methods such as geology, micro geomorphology, geophysical prospecting, geochemical prospecting, and drilling. The macro epicenter, seismogenic mechanism, and fracture mode of the earthquake were studied [1,2,[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. A series of problems such as the nature, scale, and occurrence of the main fault in the Xiadian fault zone, regional tectonic stress field the characteristics, geological tectonic background, the repeatability of large earthquakes, and the activity characteristics since the late Pleistocene are discussed as well.…”