Statistical analysis of tsunamis from multiple faults’ sequential failure with different time intervals and geographical layouts

Abstract

Earthquakes usually occur as sequential faulting that involves a rupture process, foreshock-mainshock-aftershock sequences, or earthquake swarms. While such sequential faulting lasts for several minutes for a rupture process, it may occur within a few hours, days, or even years for an aftershock followed by the main shock. Thus, sequential faulting may significantly affect the initiation of a tsunami and its subsequent propagation. In the present study, we assessed the effects of faulting kinematics on the generation and propagation of tsunamis based on numerical analysis. The Hokkaido earthquake in 1993 was modelled using three sub-faults with diverse configurations in faulting sequences and geophysical layout. The results confirmed that the tsunami height can be maximized when the faulting sequence coincides with the critical velocity (i.e., long wave speed) by introducing resonant interaction. Moreover, the geographical layout of a set of multiple faults was found to play a key role in enhancing tsunami heights, especially when the faulting process direction was normal to the coastline. Meanwhile, a statistical analysis called single spectrum analysis indicated that the faulting kinematics had the capability of changing the tsunami heights but did not alter their large-scale trend attributed to oceanic geometry.