Oceanic drilling into the northern margin of the South China Sea: investigating the great marine geohazards along the Littoral Fault Zone

The Littoral Fault Zone is a major active fault zone in the northern margin of the South China Sea, close to the coastal region of the southern China. The Littoral Fault Zone is more than 1200 km long, consisting of the west segment (Beibu Bay-Yangjiang), the middle segment (Pearl River Mouth), and the east segment (Yuedong-Fujian). At least 4 large earthquakes (magnitude>7) have occurred inthe west and east segments, while its middle segment was exempt. As the economy is rapidly growing and the present day population density is high, the littoral fault will cause enormous destruction to the coastal area of southern China if it generates great earthquakes and the ensuing tsunamis in future. Due to lack of complete historical earthquake records and oceanic drilling study on the paleoseismicity, there is lack of clarity on the precise quantity, spatial distribution and recurrence period of great earthquakes along the Littoral Fault Zone, and the nature of great earthquake quiet zone (aseismic slip or longer recurrence period of great earthquakes), which in turn leads to poor understanding of earthquake mechanism and associated risk of marine geohazards. This study summarizes the structural characteristics, describes the hazard influences of 3 large earthquakes along the Littoral Fault Zone, and introduces the international oceanic drilling studies on great earthquakes. Based on this information, we propose to carry out oceanic drilling into the west, middle and east segment of the Littoral Fault Zone, recover essential sediments and rocks through the fault zone, reconstruct the history and recurrence period of paleoseismicity along west and east parts of the Littoral Fault Zone, study the physical properties of fault zone rocks to identify the cause of earthquake quiet zone in the middle part of the Littoral Fault Zone, analyze the mechanism behavior of fault segments, finally providing critical scientific basis for the marine hazard preparedness and mitigation strategies.