Seismic hazards analysis and earthquake-induced landslide implication in the QiongDongNan segment of the continental slope fault zone (northern south China sea) revealed by dynamic rupture models

Marine earthquakes are highly dangerous. The Qiongdongnan (QDN) segment of the continental slope fault zone (CSFZ) in the northern South China Sea poses potential seismic risks, which may even trigger submarine landslides and tsunamis. Using the Curved Grid Finite-Difference Method (CGFDM), we established a dynamic spontaneous rupture model for the QiongDongNan segment of the continental slope fault zone southeast of Hainan Island, China. We then simulated wave propagation and strong ground motion resulting from these scenario earthquakes and produced seismic intensity distribution maps. The maximum magnitude achieved across all models was M_W 7.7. A left-lateral strike-slip fault with a dip angle of 59.5° was used in the scenario earthquake simulations, and 26 hypocenters were selected at various positions and depths. We further investigated the seismic waves and strong ground motions generated by these scenario events. The results indicate that the velocity structure has a significant influence on the maximum slip concentration on the fault. Additionally, under the considered initial stress conditions, earthquake magnitudes vary with the depth change for certain hypocenters. We also analyzed the potential risk of earthquake-induced landslides using the pseudo-static method and introduced the factor of safety (FOS). The results show that in the northern part of the landslide area, there is a large area where the FOS is less than 1, indicating an increased possibility of landslides. In addition, when the hypocenter is at a depth of 8 km, the earthquake with the smallest magnitude will generate a far stronger event than those with hypocenters at depths of 10 km and 12 km. Overall, this fault poses a significant risk of a chain of earthquake-landslide-tsunami disasters occurring.