Remote triggering of seismicity at Japanese volcanoes following the 2016 M7.3 Kumamoto earthquake

Bogdan Enescu,Anca Opris,Kengo Shimojo,Yuji Yagi

doi:10.1186/s40623-016-0539-5

Bogdan Enescu, Anca Opris + Show 2 more

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https://doi.org/10.1186/s40623-016-0539-5

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Abstract

The MJMA7.3 Kumamoto earthquake occurred on April 16, 2016, in the western part of Kyushu, at a depth of 12 km, on an active strike-slip fault. Here, we report on a relatively widespread activation of small remote earthquakes, which occurred as far as Hokkaido, detected by analyzing the continuous waveform data recorded at seismic stations all over Japan. Such relatively widespread remote seismicity activation, following a large inland earthquake, has not been reported before for Japan. Our analysis demonstrates that the remote events were triggered dynamically, by the passage of the surface waves from the Kumamoto earthquake. Most of the remotely triggered events in the Tohoku and Hokkaido regions, as well as close to Izu Peninsula, occur at or close to volcanoes, which suggests that the excitation of crustal fluids, by the passage of Rayleigh waves, played an important triggering role. Nevertheless, remote activation in other regions, like Noto Peninsula, occurred away from volcanoes. The relatively large-amplitude Love waves, enhanced by a source directivity effect during the Kumamoto earthquake, may have triggered seismicity on local active faults. The dynamic stresses in the areas where remote activation has been observed range from several kPa to tens of kPa, the thresholds being lower than in previous dynamic triggering cases for Japan; this might relate to a change in the crustal conditions following the 2011 M9.0 Tohoku-oki earthquake, in particular at volcanoes in NE Japan.

Highlights

Activation of seismicity at remote locations due to the passage of seismic waves from relatively large earthquakes is a well-documented phenomenon (e.g., Hill et al 1993; Brodsky et al 2000), the responsible underlying physical processes are still under debate (e.g., Hill and Prejean 2015).The static stress changes decay with distance, r, approximately proportional to r−3, for distances exceeding the source extent (Aki and Richards 2002), while the dynamic stress changes attenuate much slower
Remote events triggered during the passage of Kumamoto earthquake surface waves We show in Fig. 1 the location of seismic stations where remote earthquake triggering has been detected following the 2016 Kumamoto earthquake
The passage of mainshock Rayleigh waves might have induced volume changes, pressurizing fluids that are active triggering agents in geothermal and volcanic regions (Hill and Prejean 2015). This could be well the case for the activation of seismicity at Akita-Komagatake and Akan volcanoes (Fig. 3b, c, as well as discussion in “Remote events triggered during the passage of Kumamoto earthquake surface waves” section)

Summary

Introduction

Activation of seismicity at remote locations due to the passage of seismic waves from relatively large earthquakes is a well-documented phenomenon (e.g., Hill et al 1993; Brodsky et al 2000), the responsible underlying physical processes are still under debate (e.g., Hill and Prejean 2015).The static stress changes decay with distance, r, approximately proportional to r−3, for distances exceeding the source extent (Aki and Richards 2002), while the dynamic stress changes (due to the passage of surface waves) attenuate much slower (as r−3/2, for surface waves, Hill et al 1993). Activation of seismicity at remote locations due to the passage of seismic waves from relatively large earthquakes is a well-documented phenomenon (e.g., Hill et al 1993; Brodsky et al 2000), the responsible underlying physical processes are still under debate (e.g., Hill and Prejean 2015). Harrington and Brodsky (2006) report a relative lack of remotely triggered seismicity in Japan and propose some qualitative models to explain their observations. They find, that Kyushu (characterized by extensional tectonics and intense volcanism) shows some limited triggering following teleseismic events. They find, that Kyushu (characterized by extensional tectonics and intense volcanism) shows some limited triggering following teleseismic events. Parsons et al (2014) found as well that Japan has a relatively low triggering potential compared with other seismotectonic regions

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