Coseismic gravity and displacement changes of Japan Tohoku earthquake (Mw 9.0)

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• 作者：Xinlin Zhang^a ; ^b ; ^c ; ^{xinlinzhang2012@163.com" class="auth_mail" title="E-mail the corresponding author}Author Vitae ; Shuhei Okubo^b ; Yoshiyuki Tanaka^b ; Hui Li^a ; ^c
• 关键词：Tohoku earthquake (Mw 9.0) ; Co-seismic gravity change ; Co-seismic displacement change ; Coseismic geoid change ; Dislocation theory ; Global Positioning System ; Absolute gravity measurement ; Relative gravity measurement
• 刊名：Geodesy and Geodynamics
• 出版年：2016
• 出版时间：March 2016
• 年：2016
• 卷：7
• 期：2
• 页码：95-100
• 全文大小：1701 K

文摘

The greatest earthquake in the modern history of Japan and probably the fourth greatest in the last 100 years in the world occurred on March 11, 2011 off the Pacific coast of Tohoku. Large tsunami and ground motions caused severe damage in wide areas, particularly many towns along the Pacific coast. So far, gravity change caused by such a great earthquake has been reported for the 1964 Alaska and the 2010 Maule events. However, the spatial-temporal resolution of the gravity data for these cases is insufficient to depict a co-seismic gravity field variation in a spatial scale of a plate subduction zone. Here, we report an unequivocal co-seismic gravity change over the Japanese Island, obtained from a hybrid gravity observation (combined absolute and relative gravity measurements). The time interval of the observation before and after the earthquake is within 1 year at almost all the observed sites, including 13 absolute and 16 relative measurement sites, which deduced tectonic and environmental contributions to the gravity change. The observed gravity agrees well with the result calculated by a dislocation theory based on a self-gravitating and layered spherical earth model. In this computation, a co-seismic slip distribution is determined by an inversion of Global Positioning System (GPS) data. Of particular interest is that the observed gravity change in some area is negative where a remarkable subsidence is observed by GPS, which can not be explained by simple vertical movement of the crust. This indicated that the mass redistribution in the underground affects the gravity change. This result supports the result that Gravity Recovery and Climate Experiment (GRACE) satellites detected a crustal dilatation due to the 2004 Sumatra earthquake by the terrestrial observation with a higher spatial and temporal resolution.