摘要:
海南岛铺前港湾地区1605年发生了华南历史记录的最强烈的地震,地震强度为M7.5,地震造成陆地沉陷成海。根据野外海岸地貌调查和海岸钻孔沉积物岩性特征与粒度、元素比值分析结果,对历史地震的海岸沉积记录进行了初步的研究,4个钻孔位于铺前港湾西岸博度村附近的小型古海湾,昌德、演丰附近的野菠萝岛和道学附近的红树林区潮间带,钻孔沉积记录显示铺前港湾内湾沉陷幅度为2m,存在明显的差异性,东寨港道学和野菠萝岛附近的钻孔岩心下部为泥状红土,属于成土的风化壳顶部,根据曲口半岛下山村附近的海岸调查,强海洋动力事件形成了高出现代高潮位3.0m的高位海岸混杂沉积体,可能与1605年地震下沉引发的类似海啸的沉积事件相关。
Abstract:
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in the region around Puqian Bay, northeastern Hainan Island, which was the most extensive earthquake recorded in the historical documents in South China with the seismic intensity of MT. 5.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.
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