Possible Maximum Earthquake Tsunami Along the South Coast of China Inferred From GPS‐Derived Surface Velocities.

This study aims to assess the tsunami hazard of the maximum possible earthquake along the south coast of China. GPS‐derived surface velocities around the Manila Trench have been used to clarify the active tectonics and estimate the seismic potential of Manila subduction, where catastrophic tsunamis may originate and cause devastating damage to the surrounding area of the South China Sea. Based on the maximum potential earthquake magnitude estimated from the accumulated seismic moment, more than 100,000 possible tsunami scenarios with varying epicenters have been simulated considering the slip heterogeneity. The impact of several uncertain parameters including the release period and release ratio of accumulated seismic moment are investigated, as well as some assumptions in the model of tsunami generation. Although different release conditions for accumulated seismic moment result in a significant impact on the value of tsunami height, similar trend in spatial distribution has been shown. The results show that the tsunami wave height along the south coast of China has an increasing trend from west to east, with the maximum tsunami wave height exceeding 10 m corresponding to the potential earthquake Mw = 9.1 with a 1,000‐year release period. The impact of fault slip heterogeneity on tsunami wave height is significant. Compared to uniform slip, considering stochastic slip will increase the average tsunami wave height by about 15%. Considering locking distribution will increase the average tsunami wave height by about 20%–30% and also increase the maximum tsunami wave height by about 60%–70%. Plain Language Summary: The purpose of this study is to evaluate the tsunami hazard of the maximum possible earthquake along the south coast of China. The Manila Trench is the potential tsunami source. The first problem to be solved in the study is how large the maximum earthquake is in the Manila Trench. Therefore, the study first uses the horizontal velocity data observed by GPS stations to invert the degree of locking on the fault plane. The rate of accumulated energy is estimated based on the degree of fault locking, and then the maximum magnitude of earthquakes that may occur on the fault with different release periods is estimated. The subsequent issue to be solved is how large the tsunami generated by the maximum earthquake is. In order to fully consider the randomness of slip, the study simulated more than 100,000 possible tsunami scenarios for each earthquake magnitude. The results indicate that only considering uniform slip will significantly underestimate the tsunami hazard along the south coast of China. Key Points: Fault locking inverted by GPS‐derived surface velocities is used to estimate the seismic potential and as constraints on stochastic slipTsunami scenarios with varying epicenters and the slip heterogeneity are simulated for each estimated maximum earthquake magnitudeSensitivity analysis has been conducted considering the release period and the release ratio of accumulated seismic moment [ABSTRACT FROM AUTHOR]