Study on Seismicity and Secondary Disaster Countermeasures of Offshore Earthquake of China

According to statistics, there have been about 420 earthquakes with M6 or higher in China's coastal and offshore areas since the record, including 63 earthquakes with M7 or higher and 3 earthquakes of M8 and above, showing high major earthquake seismicity. At the same time, due to the economic growth of China in recent years, the population, infrastructure and major projects in the coastal areas have increased rapidly. Therefore, it is of great significance to study the dangers of large earthquakes in China's offshore and disaster risk countermeasures. In this paper, we use the data of the fifth generation of China Seismic Hazard Map to calculate the frequency of earthquakes in the offshore areas of China and the offshore areas above the Bohai Sea, the Yellow Sea, the East China Sea and the South China Sea, and give the major disaster risk countermeasures in the coastal and offshore areas. This paper shows that the frequency of earthquakes larger than M6 in the offshore areas of the Bohai Sea, the Yellow Sea, the East China Sea, the South China Sea and the whole region is about 0.036, 0.054, 1.03, 0.28 and 1.4 times per year respectively, and the frequency of earthquakes above M7 is about 0.014, 0.021, 0.46, 0.14 and 0.68 time per year respectively. The potential risks of land liquefaction must be guarded in the coastal and estuary delta areas. The potential risks of offshore wave storm, tsunami and land sinking must be guarded in the coastal areas of Fujian, Taiwan, Guangdong and northern Hainan.