Permalink : http://hdl.handle.net/2115/52304

JaLCDOI : 10.14943/gbhu.76.97

Wide and large coseismic displacement field around Tohoku region, northeastern Japan, are induced by the 2011 off the Pacific coast of Tohoku Earthquake. Because their effect is confirmable not only in Tohoku region, but also Hokkaido, I focus on the coseismic and postseismic strain field in Hokkaido using nationwide GPS network. A remarkable coseismic deformation is observed around southwestern Hokkaido, and the coseismic strain distribution shows also large extension with NNW-SSE direction （～ 0.6ppm）. Published fault models basically explain this coseismic deformation pattern. The displacement field during one year after the earthquake shows significant effect of postseismic deformation especially in the western part of Hokkaido. Along the Pacific coast, which parallels to Kuril trench, two different patterns appear relative to the interseismic period; smaller displacement in the eastern part （Erimo to Kushiro） , and approximately same displacement in the western part （Kushiro to Nemuro） . The shortening strain toward plate convergence direction is large in both interseismic and postseismic periods at the eastern part. It suggests that the interplate coupling around eastern Hokkaido has still continued. The relationship between postseismic strain field and shallow seismicity after the 2011 earthquake does not appear clearly at present.