高密度臨時地震観測による2004年斜里岳群発地震活動

概要

論文の詳細を見る
From April 27, 2004, Mt. Syari-dake earthquake swarm occurred in the eastern part of Hokkaido, Japan. The activity began at 4:19 on April 27, 2004. We installed nine temporary seismic stations around the seismic active area immediately after its occurrence and had continued the observation for about seven months. We determined 2228 hypocenters of earthquakes. It is found that the seismic active area is clearly distributed on the plane having southwest-northeast strike with dip angle of about 80 degrees. This plane well agrees with one of the nodal planes of the focal mechanisms of several earthquakes determined by P-wave first motions. Hypocenters migrate northeastward at a rate of 96 m/day and westward at a rate of 51 m/day. We also investigated hypocenter distribution before the installing of the temporary seismic stations. To improve accuracy of hypocenter determination we applied travel time correction for every permanent seismic stations. Relocated precise hypocenters demonstrate that the main seismic activity started to expand eastward just after the begining of the swarm.
2009-03-15