Postseismic deformation following the 2005 West Off Fukuoka Prefecture Earthquake (M7.0) derived by GPS observation

Shigeru Nakao,Hiroaki Takahashi,Yuhki Kohno,Masayoshi Ichiyanagi,Takeshi Matsushima

doi:10.1186/bf03352671

Shigeru Nakao, Hiroaki Takahashi + Show 3 more

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https://doi.org/10.1186/bf03352671

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Abstract

AbstractWe constructed a temporary GPS network around the aftershock area of the 2005 West Off Fukuoka Prefecture Earthquake (M7.0) in order to investigate the characteristics of its postseismic deformation. Our GPS network data, as well as the GEONET data, were analyzed using Bernese GPS software. We detected notable postseismic deformation in horizontal components close to the fault plane. The observed maximum displacement was 5.6 cm at the GNKI site on Genkaijima Island. A logarithmic law was adapted to the coordinate time series data, revealing decay times from 2 to 23 days, similar to those obtained for the 2003 Tokachi-oki Earthquake (M8.0). The amount of postseismic slips on the fault was assessed using the coseismic fault model proposed by the Geographical Survey Institute (GSI). We derived an optimum fault model of postseismic slip on the shallow (less than 3 km depth) portion of the fault. Our findings indicate that postseismic slip occurred only in shallow parts of the coseismic fault.

Highlights

The 2005 West Off Fukuoka Prefecture Earthquake (M7.0) took place in the northern part of Kyushu, Japan on 20 March 2005. Kato et al (1998) estimated the strain field for the event from displacement rates at the sites of the nationwide GPS network GEONET and showed that the strain rate in the focal region was no larger than that in the surrounding area
There were no GEONET sites near the focal region of the 2005 West Off Fukuoka Prefecture Earthquake, including nearby islands, such stations would have played a key role in constraining models of postseismic deformation
Significant postseismic deformation in horizontal components is clearly seen at GNKI and KTZK, while the GEONET site 021062 shown in Fig. 3 shows detectable postseismic deformations

Summary

Introduction

The 2005 West Off Fukuoka Prefecture Earthquake (M7.0) took place in the northern part of Kyushu, Japan on 20 March 2005. Kato et al (1998) estimated the strain field for the event from displacement rates at the sites of the nationwide GPS network GEONET and showed that the strain rate in the focal region was no larger than that in the surrounding area. FOR0 and QUS0 were set up on the day of the main shock while observations at four sites (KTZK, GNKI, SKSM, and NKSM) started on 21 or 22 March 2005.

Results

Conclusion