Aftershock seismicity and fault structure of the 2005 West Off Fukuoka Prefecture Earthquake (MJMA7.0) derived from urgent joint observations

Autor: Hiroaki Takahashi, Tomotake Ueno, Naoshi Hirata, Tomomi Okada, Yuhki Kohno, Masaki Saito, Masayoshi Ichiyanagi, Norimichi Matsuwo, Takeshi Matsushima, Bogdan Enescu, T. Yagi, Kazuhiko Goto, Taku Urabe, Kazuo Nakahigashi, Tomoaki Yamada, Nobuki Kame, Shin’ichi Hashimoto, Hiroshi Shimizu, Naoki Uchida, Mio Hori, Kazunari Uchida, Toshihiko Kanazawa, Masanao Shinohara, Syuichiro Hirano, Kenji Uehira, Yoshihisa Iio, Satoshi Matsumoto, Hiroki Miyamachi, Watanabe Atsushi, Shigeru Nakao, Hiroshi Yakiwara, Takaya Iwasaki, Hiroshi Katao
Rok vydání: 2006
Předmět:
Zdroj: ResearcherID
ISSN: 1880-5981
DOI: 10.1186/bf03352668
Popis: On March 20, 2005, a large M JMA7.0 earthquake occurred in the offshore area, west of Fukuoka prefecture, northern Kyushu, Japan. A series of joint observations were carried out by teams from several universities in Japan with the aim of investigating the aftershock activity. Six online telemetered and 17 offline recording seismic stations were installed on land around the aftershock area immediately followed the occurrence of the mainshock. Because aftershocks were located mainly in offshore regions, we also installed 11 ocean bottom seismometers (OBSs) just above the aftershock region and its vicinity in order to obtain accurate locations of hypocenters. The OBS observation was carried out from March 27 to April 13, 2005. We further conducted temporary GPS observations in which ten GPS receivers were deployed around the aftershock region. The aftershocks were mainly aligned along an approximately 25-km-long NW-SE trend, and the hypocenters of the main aftershock region were distributed on a nearly vertical plane at depths of 2–16 km. The mainshock was located near the central part of the main aftershock region at a depth of approximately 10 km. The largest aftershock of M JMA5.8 occurred near the southeastern edge of the main aftershock region, and the aftershock region subsequently extended about 5 km in the SE direction as defined by secondary aftershock activity. Enlargement of the aftershock region did not occur after the peak in aftershock activity, and the aftershock activity gradually declined. The distribution of hypocenters and seismogenic stress as defined by aftershocks suggest that the 2005 West Off Fukuoka Prefecture Earthquake occurred on the fault that is the NW extension of the Kego fault, which extends NW-SE through the Fukuoka metropolitan area, and that the largest aftershock occurred at the northwestern tip of the Kego fault.
Databáze: OpenAIRE