Stress buildup and drop in inland shallow crust caused by the 2011 Tohoku-oki earthquake events

Kiyotoshi Sakaguchi,Noriaki Watanabe,Tatsuya Yokoyama,Weiren Lin

doi:10.1038/s41598-017-10897-8

Kiyotoshi Sakaguchi, Noriaki Watanabe + Show 2 more

Open Access

https://doi.org/10.1038/s41598-017-10897-8

Copy DOI

Abstract

To examine the change in stress between before and after the Tohoku-oki Mw9.0 earthquake, we performed stress measurements after the earthquake in the Kamaishi mine in Iwate prefecture in northern Japan, located near the northern termination of the mainshock rupture, following previous measurements before the earthquake in the same mine. The results showed that the magnitudes of the three-dimensional principal stresses and the vertical stress drastically increased after the mainshock and, at 1 year after the earthquake, were more than double those before the earthquake. The principal stress magnitudes then decreased with time and returned to almost pre-earthquake levels at about 3 years after the earthquake. These changes can be interpreted in terms of coseismic rupture of the mainshock and the occurrence of aftershocks in the Sanriku-oki low-seismicity region (SLSR), where the Kamaishi mine is located. The drastic increase in stress suggests that the SLSR may act as a barrier to further rupture propagation.

Highlights

Stress and earthquakes are known to be interrelated: stress triggers earthquakes and earthquakes alter the shear and normal stresses in surrounding faults[1,2,3,4,5]
The Kamaishi mine was originally developed as an underground metal mine and is not currently operational
It has been reported that the coseismic surface crustal movement during the earthquake in this region consisted of horizontal movement of 3.32 m and subsidence of 0.5 m23

Summary

Introduction

Stress and earthquakes are known to be interrelated: stress triggers earthquakes and earthquakes alter the shear and normal stresses in surrounding faults[1,2,3,4,5]. In situ rock stress is an important concern in the construction of tunnels and underground caverns at depths of tens or even several hundreds of metres For such purposes, several in situ rock stress measurements have been performed at the Kamaishi mine in northeast Japan (Fig. 1(a)) from 1991 to 200710–15. The coseismic slip of the plate interface below the Kamaishi region during the Tohoku-oki earthquake was relatively slight[16,17,18,19] (Fig. 1(a)), and this may have acted as a barrier to further rupture propagation during the earthquake. It is important to clarify the change in the absolute magnitude of stress before and after the earthquake For this purpose, the results of stress measurements before the earthquake are indispensable, because they cannot be obtained after the earthquake. We regularly repeated stress measurements at the same research site in the Kamaishi mine after the earthquake using the same method as studies conducted prior to the earthquake

Methods

Results

Conclusion