PRELIMINARY STUDY ON THE COASTAL SEDIMENTS RECORDS ABOUT THE HISTORICAL EARTHQUAKE IN THE YEAR OF 1605, HAINAN ISLAND, CHINA

The serious earthquake in the year of 1605 occurred at Qiongshan in the region around Puqian Bay, northeastern Hainan Island, which was the most extensive earthquake recorded in the historical documents in South China with the seismic intensity of MT. 5. This historical earthquake resulted in the land subsidence and the formation of the Puqian Bay. According to the recent investigation of coastal landforms, sedimentary characteristics of the boreholes and the analysis results about the grain size and element ratios, a preliminary study on the coastal sedimentary records about the historical earthquake was presented in this paper. Four boreholes were located at the abandoned bay close to Bodu village and in the mangrove tidal flat near Changde village, Yeboluo Island and Daoxue respectively. The comprehensive analysis indicated the 2.0 m subsidence occurred at the inner part of the Puqian Bay. The boreholes at Daoxue and Yeboluo Island penetrated to the buried red soil, which was the terrestrial environment before the earthquake subsidence. The most interesting finding of coastal landform investigation along the Qukou Peninsula, mid-western Puqian Bay was the coastal gravel-sand deposit 3 m higher than the present high sea level, which was formed in the strong coastal dynamics and may be related to the influence of tsunamilike wave during the earthquake subsidence in the year of 1605. Further detailed study is needed for the analysis about the sediment chronology.