著者

小林 知勝

出版者

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)

雑誌

北海道大学地球物理学研究報告 (ISSN:04393503)

巻号頁・発行日

vol.72, pp.257-268, 2009-03-15

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A feasibility test of a kriging method is conducted for estimate of a strain field. In this test the kriging method is applied to man-made data and actual ground displacement data observed in Taiwan. It is investigated how well the method can reproduce the given strain field and extract the complex strain field of Taiwan. To clarify the merits/demerits of this method, we compare the results of the kriging to those inferred from other analysis methods; one is a conventional method in which a strain is directly calculated using a triangulation network and the other is a method incorporating a spatial smoothing procedure. The results demonstrate that the kriging method enables us to provide a largescale strain field spatially smoothly, and further to simultaneously extract a localized deformation. Additionally it is noteworthy that this method is robust for anomalous data, i.e., weights of anomalies are suppressed automatically. On the other hand, the standard triangulation method cannot stably extract a large-scale strain field and at a certain case artificial strain errors are produced. This method is very sensitive to anomalous data and/or even to small fluctuations (errors) of data. The method incorporating a spatial smoothing procedure that has been developed and applied in many recent studies can robustly evaluate strain components that are spatially dominant in the analyzed domain, but miss out a small-scale deformation due to the smoothing.

著者

小山 順二 本谷 義信 原 啓明

出版者

北海道大学大学院理学研究科地球惑星科学専攻(地球物理学)

雑誌

北海道大学地球物理学研究報告 (ISSN:04393503)

巻号頁・発行日

vol.60, pp.77-95, 1997-03-31

著者

森谷 武男

出版者

北海道大学大学院理学研究科地球惑星科学専攻(地球物理学)

雑誌

北海道大学地球物理学研究報告 (ISSN:04393503)

巻号頁・発行日

vol.60, pp.61-75, 1997-03-31

著者

田村 慎 一柳 昌義 笠原 稔

出版者

北海道大学大学院理学研究科地球惑星科学専攻(地球物理学)

雑誌

北海道大学地球物理学研究報告 (ISSN:04393503)

巻号頁・発行日

vol.65, pp.127-142, 2002-03-25

著者

岡崎 紀俊 一柳 昌義 Gordeev Evgenii 笠原 稔

出版者

北海道大学大学院理学研究科地球惑星科学専攻(地球物理学)

雑誌

北海道大学地球物理学研究報告 (ISSN:04393503)

巻号頁・発行日

no.64, pp.165-181, 2001-03

著者

三品 正明 立花 憲司 三浦 哲

出版者

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

雑誌

北海道大学地球物理学研究報告 (ISSN:04393503)

巻号頁・発行日

no.72, pp.287-298, 2009-03

被引用文献数

1

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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.