Undersea co-seismic crustal movements associated with the 2005 Off Miyagi Prefecture Earthquake detected by GPS/acoustic seafloor geodetic observation

Yoshihiro Matsumoto,Tetsuichiro Yabuki,Akira Asada,Masayuki Fujita,Masashi Mochizuki,Tadashi Ishikawa

doi:10.1186/bf03352663

Yoshihiro Matsumoto, Tetsuichiro Yabuki + Show 4 more

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https://doi.org/10.1186/bf03352663

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Abstract

Abstract We have been carrying out seafloor geodetic observations at two reference points situated off Miyagi Prefecture, northeastern Japan, using the GPS/Acoustic combination technique. Comparison of position estimates before and after the 2005 Off-Miyagi Prefecture Earthquake revealed a co-seismic crustal movement as large as 10 cm eastward at the site approximately 10 km from the epicenter, while no prominent movement was found at another site located 60 km away from the epicenter. The results at these two sites are consistent with crustal deformation calculated from the rectangular dislocation model on the fault derived from crustal movements observed at GEONET stations on land.

Highlights

Off-shore of Miyagi Prefecture is one of the most seismogenic zones in Japan where a major convergent plate boundary, the Japan Trench, is located
We present and discuss the undersea coseismic crustal movement associated with the 2005 Off Miyagi Prefecture Earthquake that we have detected at our seafloor reference points during our intensive observations carried out in 2005
The estimated vector of the movement of the seafloor reference point MYGW from our observation is shown in Fig. 4, with superposed synthetic vectors of crustal deformation predicted by this model at MYGW and MYGI

Summary

Introduction

Off-shore of Miyagi Prefecture is one of the most seismogenic zones in Japan where a major convergent plate boundary, the Japan Trench, is located This region has experienced huge interplate earthquakes repeatedly at relatively regular intervals of 30–40 years. GPS observations at the GEONET stations on land detected horizontal movements of approximately 6 cm at most from the southeast to the east extensively in and around Miyagi prefecture and subsidences of approximately 5 cm at most in the Oshika peninsula (GSI, 2005) These observations on land produced a fault model that was mostly consistent with the focal mechanism and distribution of aftershocks (JMA, 2005), it is desirable to have data in the offshore region closer to the undersea focal area to better constrain the slip distribution estimation in the rupture area

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Discussion

Conclusion