Earth Planets Space, Vol. 54 (No. 11), pp. 1059-1063, 2002
Takeshi Sagiya1, Takuya Nishimura1, Yoshihisa Iio2, and Takashi Tada1
1Geographical Survey Institute, 1 Kitasato, Tsukuba, Ibaraki 305-0811, Japan
2Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
(Received January 11, 2002; Revised August 11, 2002; Accepted August 12, 2002)
Abstract: We established a dense permanent GPS array around the northern and central Itoigawa-Shizuoka Tectonic Line (ISTL) in order to study loading processes of inland active faults. 1-4 years observation has revealed concentrated deformation (about 0.3 ppm/yr) around the East Matsumoto-Basin Fault, an active fault along the ISTL, consistent with historic triangulation data. The deformation pattern is explained by dislocation models incorporating horizontal detachment fault with steady slip in the upper crust. However, deformation data alone cannot determine the model and there exist different possibilities. The vicinity of the Gofukuji fault is being deformed less in spite of the large long-term slip rate. These observations indicate that the deformation pattern is laterally heterogeneous along the ISTL. The two faults are considered to be loaded by different mechanisms.