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In order to estimate the horizontal strain of southwest Japan for the period of Nov.1997 to Nov2000, using GPS data of the Geographical Survey Institute of Japan, after making an unbiased data, we der...ived two empirical covariance functions by applying least-square prediction method. During a repeated calculation, we compared the effect of correlation distances with the measurement vectors of different points and partitioned whole Japan into two main regions, where the correlation distances for two E-W and N-S components could be equal. The partitioning boundary has a good coincidence with the Fossa Magna which is considered to be a plate boundary between the Okhotsk and the Eurasian plates. We estimated the correlation distance of southwest Japan as 250 km and derived two new covariance functions to compute the horizontal strain of this region. During Nov.1997-Nov. 1998, from central to east Kyushu, there is a widespread shear anomaly, 0.24×10 ^ -6
yr, that may refer to the effect of the Hyuganada earthquakes on Oct.19, 1996 and Dec. 03, 1996. Also this anomaly is extended into Shikoku Island and could be related to some slow slip displacements because of lacking any large events. Most of the Shikoku Island is under shear strain that extended to the southern part of the Kinki area too. The strain state in southwest Japan is characterized by NW-SE contraction in most places that may be attributed to the convergence of the Eurasian, the Philippine Sea and the Pacific plates. In central Kyushu Island, N-S extension could be due to the mantle pluming under western off Kyushu. Also the NW-SE and E-W extension in the southwestern part of Kyushu and west off Yakushima Islands could be caused by the expansion of the Okinawa trough.続きを見る
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Mendeley出力
31_03_p093