High-resolution tsunami hazard assessment for the Guangdong-Hong Kong-Macao Greater Bay Area based on a non-hydrostatic tsunami model

Abstract

The Guangdong-Hong Kong-Macao Greater Bay Area (GBA) is threatened by potential tsunami hazards from the Littoral Fault Zone (LFZ) and the Manila subduction zone (MSZ), and may suffer huge damage because of its dense population, concentrated infrastructure, and low-lying coasts. Previous tsunami studies for the GBA made simple assumptions on the mechanisms of LFZ earthquakes, and used coarse bathymetry data in tsunami simulation, which limited the prediction of detailed tsunami hazard characteristics. In this paper, we develop a parallel dispersive tsunami model PCOMCOT to efficiently simulate dispersive, nonlinear, and breaking tsunami waves. We also construct large-scale and high-resolution bathymetry models for the GBA by correcting and integrating various data sources. Dynamic rupture simulation is performed for the LFZ to obtain a more reliable earthquake source model. We propose several representative earthquake scenarios for the LFZ and MSZ, and use PCOMCOT to calculate the resulting tsunami waves, currents, and inundation in the GBA. Our results indicate that if an M_w7.5 oblique-slip earthquake occurs in the LFZ off the Pearl River Estuary (PRE), the subsequent tsunami will primarily impact Hong Kong, causing maximum positive and negative waves of around 1 m and −2 m, respectively, along with slightly destructive currents (⩾1.5 m/s). An M_w9.0 MSZ megathrust earthquake can lead to widespread inundation with >1 m depth on the outlying islands of Macao and in the urban areas of Hong Kong around the Victoria Harbour. Besides, it will also cause catastrophic tsunami currents along the narrow waterways in Hong Kong and Macao, and the spatial distribution of strong currents (⩾3 m/s) shows a considerable discrepancy from the areas of serious inundation. Thus, more attention should be paid to the potential impacts of tsunami currents on the GBA.