Earthquake triggering model based on normal-stress-dependent Nagata law: application to the 2016 Mie offshore earthquake

Shingo Yoshida,Takuto Maeda,Naoyuki Kato

doi:10.1186/s40623-020-01272-5

Abstract

We propose a normal-stress-dependent Nagata law. Nagata et al. (J Geophys Res 117:B02314, 2012) revised the rate- and state-dependent friction law by introducing the shear stress dependence. We further extended the Nagata law by incorporating the normal stress dependence obtained by Linker and Dieterich (J Geophys Res 97:4923–4940, 1992). We performed numerical simulations of earthquake triggering by assuming the extended Nagata law. In the case of repeated earthquakes, we applied dynamic Coulomb failure function (CFF) perturbation due to normal or shear stress changes. CFF perturbation increased the slip velocity after the cessation of perturbation, relative to that of the repeated events without triggering. This leads to dynamic earthquake triggering for certain perturbation amplitudes with time to instability of 0 to several tens of days. In addition, triggering potential of the static CFF jump (ΔCFFs) was investigated. Static stress perturbation has a higher triggering potential than dynamic stress perturbation for the same magnitude of CFF. The equivalent ΔCFFeq is evaluated for dynamic perturbation that results in a triggering potential approximately the same as in the case of static stress perturbation if ΔCFFs = ΔCFFeq. We calculated ΔCFFeq on the interface of the Philippine Sea plate for the Mie offshore earthquake, which occurred around the Nankai Trough on April 1, 2016, using OpenSWPC. The results shows that ΔCFFeq is large around the trough, where slow slip events followed the Mie earthquake, suggesting that a large ΔCFFeq may have triggered slow slip events.

Highlights

A likely mechanism behind earthquake triggering has been based on the rate- and state-dependent friction (RSF) law (Dieterich 1979; Ruina 1983)
After the 2016 Mie offshore earthquake, shallow slow slip events (SSEs), shallow very low-frequency events, and shallow tremor were observed near the Nankai trough, which were probably triggered by the Mie offshore earthquake (Annoura et al 2017; Araki et al 2017; Nakano et al 2018)
They considered that a SSE accompanied by these tremors was triggered by the 2016 Mie offshore earthquake

Summary

Introduction

There have been many reports of earthquake triggering (e.g., Hill et al 1993; Brodsky et al 2000; Kilb et al 2000; Miyazawa et al 2008; van der Elst and Brodsky 2010; Richards-Dinger et al 2010; Miyazawa 2011; Parsons and Velasco 2011; Lin 2012; Pollitz et al 2012; van der Elst et al 2013; Yukutake et al 2013; Johnson and Bürgmann 2016; Miyazawa 2016; Uchida et al 2016; Yoshida 2016). Dieterich (1994) obtained the time to instability as a function of slip velocity based on a spring-block model, and found that an increase in the slip velocity due to a static stress change could trigger an earthquake.

Results

Conclusion