One of the important tasks in the on-site fault assessment of nuclear power plants is the estimation of fault displacements and their impact on the safety functions of facilities. Numerical prediction is one of the preferable methods for estimating fault displacements. The author proposes a numerical prediction method for estimating surface fault displacement using the dynamic fault rupture analysis. The proposed method is applied to the 2016 Kumamoto earthquake with surface faulting.

In this study, both primary and secondary faults are considered. For the primary faults, the fault rupture is initiated at a predefined hypocenter, and programmed to propagate outward along the fault plane with specified rupture velocities and stress drops until it is arrested at the edge of the fault plane. The calculation of the surface slip distribution on primary faults was consistent with the measured slip value. In the simulation, surface slip also appeared on the secondary faults. However, the calculated values of the surface slips on the secondary faults were not as consistent with the measured slip values. Therefore, the proposed numerical method is applicable to evaluating the possibility of surface slip on secondary faults. In the simulation, the appearance of the surface slip almost coincided with the occurrence of strong vibrations along the secondary faults.

1. Introduction

One of the aftermaths of the 1999 massive earthquakes in Taiwan and Turkey is the growing concerns regarding the potential damage to various infrastructures and buildings caused by surface fault ruptures. Therefore, for the on-site fault assessment of nuclear power plants (NPPs), it is important to estimate the fault displacement and their impact on facility safety functions. Detailed geological surveys showed that important facilities in the NPPs were separated from the primary faults that are a direct extension from the earthquake fault source. Nevertheless, there are several cases of secondary faults beneath or close to these important facilities. Research has explored the activities of such faults. Estimating fault displacement is a crucial issue in on-site fault assessment. Numerical simulation has the potential to provide a reliable estimation of fault displacement.

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