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Title: 孔井式歪計によって観測された福島県沖の地震に伴った余効変動
Other Titles: Postseismic deformation associated with off Fukushima Earthquakes as inferred data of borehole strainmeters
Authors: 三品, 正明1 Browse this author
立花, 憲司2 Browse this author
三浦, 哲3 Browse this author
Authors(alt): Mishina, Masaaki1
Tachibana, Kenji2
Miura, Satoshi3
Issue Date: 15-Mar-2009
Publisher: 北海道大学大学院理学研究院自然史科学部門(地球物理学)
Journal Title: 北海道大学地球物理学研究報告
Journal Title(alt): Geophysical bulletin of Hokkaido University
Volume: 72
Start Page: 287
End Page: 298
Abstract: Borehole strainmeters installed in the coastal area of Miyagi and Fukushima prefectures recorded the remarkable postseismic strain change following earthquake off Fukushima Prefecture on July 19, 2008 (M 6.9). Using exponential function, we simulated the postseismic strain change and obtained time constant and amplitude of the postseismic change. Time constant was 57 h. The amplitude ratio to the amplitude of the co-seismic change was 0.9 (KNK: Kinkazan), 1.1 (EN3: Enoshima) and 1.6 (MH2: Mihodo), respectively. This means almost the same amount of slip as the main shock occurred on the fault plane after the shock. We also analyzed data at an off Fukushima Prefecture earthquake on October 31, 2003 (M 6.8). Time constant of the postseismic change was 40 h. The amplitude ratio was 0.5 (KNK), 0.6 (EN3) and 1.5 (MH2), respectively. This earthquake also had similar feature as the 2008 event. These characteristics of postseismic slips are considered to relate the distribution of the coupling coefficient between Pacific plate and continental plate. In off Fukushima area, the coupling coefficient may be weaker around the epicenter area of the 2008 earthquake than around the 2003 event.
Type: bulletin (article)
Appears in Collections:北海道大学地球物理学研究報告 = Geophysical bulletin of Hokkaido University > 第72号

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