open access

https://hdl.handle.net/2115/57960

Aftershock Distribution of the December 14, 2004 Rumoi-nanbu Earthquake ($M_{JMA}$ 6.1) in the Northern Part of Hokkaido, Japan

日本語

Reverse fault

2007-03-15

日本地震学会

地震. 2輯

59(3)

209-221

On December 14, 2004, an M 6.1 earthquake occurred in the northwestern part of Hokkaido, Japan. We installed nine temporal seismic stations around the source area immediately after the occurrence and had continued the observation for about two months after the main shock. We determined 823 hypocenters of aftershocks and one dimensional P-wave velocity structure model from the travel time data. It is found that aftershocks are clearly distributed on an eastward dipping plane with a dip angle of about 25 degrees. This plane agrees well with one of the nodal planes of the focal mechanism determined by P-wave first motions in this study. Next, we investigated a position of the main shock relative to the aftershock distribution. The station correction values for permanent stations were determined from the data during the period of the temporary observation. Estimated main shock hypocenter was confirmed to be situated on the aftershock plane. Finally, we estimated three-dimensional P-wave velocity structure based on the temporary travel time data. Relocated aftershocks using the three dimensional velocity structure were mainly distributed along the boundary between the high and low velocity zones.

学術雑誌論文

Version of Record

0037-1114

1883-9029