Recent dynamic crustal movements in the Tokai Region, Central Japan, observed by GPS Measurements

Abstract

We present the recent dynamic crustal movements in the Tokai Region, Central Japan, observed by Global Positioning System (GPS) measurements. Since October 2000 the abnormal crustal movements began to move southeastward in the area inland Tokai Region, the reverse motion to the secular crustal movements, suggesting the slow slip between the subducting Philippine Sea slab and the subducted southwest Japan (SWJ). The abnormal crustal movements were fast and wide during October 2000 and December 2001, and slow and narrow during January and December 2002, and again fast and wide during January 2003 and April 2004. Since around June 2004, the abnormal crustal movements became again slow and narrow, and then in September 2004 a M7.4 earthquake occurred at around 200 km southern southwest of the Tokai Region near the Nankai Trough. Co-seismic motions are southward 10–30 mm displacement in the Tokai Region. Since the occurrence of the earthquake the southward motion began in the southeast end of SWJ including the Tokai Region. On the other hand the abnormal crustal movements are still ongoing to be slow and narrow.