Palaeotsunami in the East China Sea for the past two millennia: A perspective from the sedimentary characteristics of mud deposit on the continental shelf

Abstract

Palaeotsunami studies have revealed that a great tsunami occurred in the South China Sea (SCS) and hit Xisha Archipelago a thousand years ago, suggesting the risk of tsunami hazard in this region. However, knowledge about palaeotsunamis in the East China Sea (ECS) is still limited. In this study, the grain size sequence of a marine sediment core was analyzed and the history of tsunamis in the East China Sea for the past two millennia is presented. We first conducted a numerical simulation of the SCS tsunami to see its impact on the ECS. The results suggest that the impact of an Mw 8.0 earthquake-induced tsunami is small. For the sediment core, according to its mean grain size distribution, the sediments were formed by two components, the <57.8 μm fraction and the >57.8 μm fraction, consisting about 90% and 10% of the core. The most significant change in the grain size sequence of the <57.8 μm fraction is consistent with the SCS tsunami temporally and this might be the result of the westward transportation of coarse grains by the tsunami. For other abrupt changes in the grain size sequence, they have not exhibited greater amplitudes than the tsunami-affected layer, indicating that the impact of the SCS tsunami was the most significant during this period. Thus, the East China Sea has not been struck by great tsunamis in the past two millennia. For palaeotsunamis occurring before the late-Holocene, more studies based on various proxies are required to reveal their history.