Probabilistic Tsunami Hazard Assessment (PTHA) for Southeast Coast of Chinese Mainland and Taiwan Island

Abstract

Tsunami impacts along the coastline of Chinese Mainland received little attention until the 2011 M w 9.0 Tohoku earthquake and tsunami devastated the neighboring country of Japan and produced 30-60 cm wave amplitudes along the East China coasts (Figure 1). In the wake of the Tohoku event, the emergency authorities of China started to ponder how a similar event elsewhere in the Pacific Rim might affect the coastal fringe of China, where the coastal communities built on low land with hundreds of millions of residents and vast infrastructures would be devastated by severe coastal inundation.For a long period of time, the tsunami hazards in Chinese Mainland were not fully addressed due to two main reasons: a vast and shallow Abstract A Probabilistic Tsunami Hazard Assessment (PTHA) study on the Chinese Mainland and the Taiwan Island was conducted. Characterized by broad and shallow continental shelves, the offshore region along Chinese Mainland's east coast yields a significant nonlinear effect and bottom friction to the propagating long waves. To address these shallow-water effects, a fully nonlinear Boussinesq model was used in the computation-based PTHA framework. We found that the inappropriate usage of the linear wave model could considerably overestimate the tsunami hazards along the East China Sea (ECS) and the Yellow Sea. Tsunami hazard along the coastline of Chinese Mainland is generally moderate. Elevated tsunami hazard levels are found along both flanks of the Yangtze and Pearl estuaries. The probability of these coastlines impacted by 1 m or greater tsunami waves (at 10-m isobath) is about 14%-40% in next century. The shallow and tongue-shaped submarine terrain amplifies the hazard level by trapping the tsunami energy in these areas. Major subduction zones in the Northwest Pacific were identified as the main sources of destructive events along the coast of ECS and the Taiwan Island, while the Manila Trench is the main source zone that threatens the Northern South China Sea. The tsunami hazards generated by the crustal earthquakes are modest, yet not negligible, particularly in the Taiwan Strait. We found the risk of tsunami inundation along the coast of Shanghai is low based on the hazard curves of total water level that incorporates the aleatory uncertainty of tides. Plain Language Summary Tsunamis are infrequent yet devastating natural hazards. Most tsunami waves are generated by underwater earthquakes, and propagate onshore with transformation of wave amplitude and wave length. The Probabilistic Tsunami Hazard Assessment is a quantitative means to estimate the probability of tsunamis affecting the coastal areas of interest, with the purposes of enhancing public awareness and assisting disaster-mitigation activities. Our study aims to address the common concerns of whether the subduction zones in the Pacific Ocean and the local crustal faults may endanger China's low-lying coastal areas that are susceptible to tsunami inundation. The main finding of the study is that both flanks of the Yangtze Estuary a...

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

“…This is similar to the results of the probabilistic tsunami hazard assessment completed by Zhang and Niu (2020) and Yuan et al. (2021), where tsunami hazard increases from west to east. On the one hand, the eastern region is closer to the source area, and on the other hand, the influence of local terrain, such as the presence of Taiwan Island, may increase the tsunami hazard in adjacent areas.…”

“…Considering only stochastic slip, the tsunami wave height increase of 25 target points ranges from 7.50% to 28.19%, with an average of 15.12%. The simulation results of this study are similar to previous studies (Li et al., 2016; Yuan et al., 2021), and considering only the uniform slip model will significantly underestimate the tsunami hazard. Considering stochastic slip will increase the tsunami hazard by about 15%.…”

“…In early studies, uniform slip distribution was commonly used to simulate tsunamis. But now, it is widely recognized that uniform slip models will underestimate tsunami hazard (Li et al., 2016; Melgar et al., 2019; Yuan et al., 2021), so stochastic slip models are often used. The existing stochastic slip models are mostly based on Herrero and Bernard's (1994) k‐squared model, such as Gallovič & Brokešová's (2004) Hybrid k‐2 Slip Generator and Mai and Beroza's (2002) Code for Earthquake Rupture and Ground‐motion Simulation (CERS).…”

Tsunami risk research on coastal areas in Fujian Province, China

“…Because of the protection of the island chains, China seems not to be influenced by the tsunami, seriously. However, based on statistics of historical earthquake events, there have been earthquakes in the south China sea and yellow sea [8,9], and regional and distant tsunami from the northwest Pacific Ocean cannot be neglected under extreme situations [7]. At the same time, in the coastal cities of southeast China, the economy is developed and the population density is large.…”

Investigation of Local Tsunami Effect on Coastal Areas: A Case Study of Putian City, Fujian Province, China

“…The potential tsunami sources off the Chinese seas have been studied extensively [1,2]. The regional tsunami sources are concentrated mostly in the Ryukyu and Manila Trench, and the Manila Trench has a high tsunami risk to the adjacent seas [3,4]. Potential tsunami threat from the Manila Trench has been broadly studied in recent years since it will affect almost the entire Chinese southeastern coastlines once a significant earthquake occurs at this area [5][6][7][8].…”