Probabilistic Tsunami Hazard Assessment for the Southeast Coast of China: Consideration of Both Regional and Local Potential Sources

The South China Sea (SCS) is recognized as a zone at high risk of tsunamis, which makes surrounding areas suitable for conducting probabilistic tsunami hazard assessment (PTHA). Most previous PTHAs were conducted with consideration of either local or regional potential tsunami sources (PTSs). In this study we developed a PTHA framework for the coastal area of southeastern China that considers the impact from both types of PTS together. First, the seismic activity of the Manila regional PTS was evaluated based on catalogs of historical earthquake and tsunami events. Through consideration of three conditions (earthquake magnitude, focal depth, and focal mechanism), the annual rate of occurrence of a tsunamigenic earthquake (a low limit earthquake magnitude is set as 7.0) was estimated to be 0.01. Second, 1400 scenario tsunamis were produced randomly and their wave propagation was numerically simulated. Tsunami hazard maps were delineated displaying wave heights in terms of 475-, 975-, 2475-, and 4975-year return periods. Regional variation in the tsunami hazard was revealed for the coast of southeastern China. Coastal regions of southern and central Fujian Province (24°–25.5°N) were projected to have the highest level of hazard because they are not only geographically close to, but are also positioned perpendicular to, four local PTSs. The tsunami hazard curves of six major cities/regions (Macao, Hong Kong, Daya Bay, Shantou, Xiamen, and Quanzhou) were examined as typical cases. It was revealed that local PTSs and the Manila regional PTS separately dominate the tsunami hazard at different locations, indicating that tsunami mitigation measures may need to be locally adapted to the dominant source.