Application of comprehensive geophysical-drilling exploration to detectthe buried Shunyi active fault belt in Beijing, China

Shunyi fault is one of important buried faults in Beijing, the capital of China. The Quaternary activity and ground deformation of this fault are important for optimizing the pattern of land space development, and constructing disaster prevention and mitigation system in Beijing. Since the buried active fault is complex, we used the controlled source audio-frequency magnetotelluric (CSAMT), shallow seismic reflection, high density resistivity and drilling exploration to detect its location, character and activity intensity. The results show that the trending of Shunyi fault is NE, dip direction is SE, and is a normal fault. The Shunyi fault is an active fault with variable activity: its vertical activity rate was 0.23mm/a since the Early Pleistocene, 0.03mm/a since the Mid-Pleistocene, 0.29 mm/a since the Late Pleistocene, and 0.51 mm/a since the Holocene in Beixiaoying town. There were spatial and temporal disparities in the Shunyi fault activity since Quaternary. It was strongly active in the Early Pleistocene but showed weaker activity during the Middle Pleistocene. In the Late Pleistocene, the activity of Shunyi fault was enhanced, and the strongest activity occurred in the Holocene. It's worth noting that south segment of Shunyi fault had stronger activity than north segment since the Quaternary, and is still active, which may explain why the ground fissures appeared in Shunyi recently. Obviously, active faults control ground fissures in Shunyi area.