open access

https://doi.org/10.14943/gbhu.72.287

https://hdl.handle.net/2115/38160

Postseismic deformation associated with off Fukushima Earthquakes as inferred data of borehole strainmeters

日本語

2009-03-15

Department of Natural History Sciences (Geophysics), Graduate School of Science, Hokkaido University

Geophysical bulletin of Hokkaido University

72

287-298

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.

紀要論文

Version of Record

0439-3503

AN0008976X