On comprehensive application of seismic reflection and MASW method for investigation of urban subsurface active faults and underneath structures: A case study in Haikou city of Hainan province, China

Abstract

Tectonically, northeast of Hainan Island belongs to the south part of Lei-Qiong sag, and experienced a great subsidence process during the Cenozoic. It is likewise the strongest earthquake activity area on Hainan Island. In 1605, an M7.5 earthquake occurred in the northeast of Hainan Island, which caused a large area of land subsidence into the sea, and initially formed the present pattern of Dongzhaigang Bay in northeast Hainan Island. Previous studies have shown that the seismogenic fault of this earthquake was the Maniao-Puqian fault. About this fault, there has been a lack of in-depth research on the fault activity, the controlled subsidence process, and the state of the underground structure in this area since the late Cenozoic. To investigate the latest active age and the specific location distribution of the Maniao-Puqian fault, and the influence of its normal fault on the subsidence of the Dongzhaigang area, detailed investigation work has been done on this fault area, through the near-surface seismic reflection and Multichannel Analysis of Surface Wave (MASW) method. The results of near-surface seismic exploration showed that the Maniao-Puqian Fault belt is composed of a group of north-dipping normal faults with a near east-west distribution, which was named Maniao-Luodou fault, Guilingyang-Qiaotoucun fault, and Xixiu-Puqian fault. This differs from previous research that the Maniao-Puqian Fault belt is an en echelon type fault. This work redefines the nature and distribution of active faults in Haikou City, which can provide important technical support for the site selection of critical infrastructure construction in the Jiangdong New district of Haikou City.