Rupture Dynamics of the Middle Section of Littoral Fault Zone: Potential Maximum Magnitude and Cascading Rupture Analysis

Abstract In the northern part of the South China Sea lies a tectonic belt with frequent seismic activity, which is known as the Littoral Fault Zone (LFZ). The middle part of this fault zone is adjacent to the Guangdong–Hong Kong–Macao Greater Bay Area (GBA). The LFZ comprises three main fault segments characterized by complex tectonic features and high seismicity. Using the curvilinear grid finite-difference method, we first conducted a 3D spontaneous dynamic rupture simulation of potential earthquakes on a multifault model of the LFZ. Under a reasonable range of physical parameter constraints, we explored a reference dynamic model and a critical dynamic model. Then, based on the critical dynamic model that could trigger extreme earthquake scenarios, we performed dynamic rupture simulations by setting six hypocenters in areas with high static stress drops on the three main fault segments. The simulation results indicated that the easternmost fault segment (F3) which is closer to Shenzhen and Hong Kong could generate the largest possible earthquake with a magnitude up to Mw 7.47. Considering a ± 10° uncertainty in stress orientation, the potential maximum magnitude can reach Mw 7.59. Furthermore, the results suggested a low likelihood of cascading rupture across the three fault segments, due to generally low stress drops at the boundaries between faults, which hinder the rupture jumping. Thus, we concluded that the probability of the LFZ generating an extreme earthquake (Mw≥7.6) affecting the GBA is relatively low. Given these results, future efforts to mitigate seismic disasters in the GBA should especially focus on areas near the easternmost fault segment, F3.