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Experimental Study on Near-Fault High-Frequency Strong Motion

Research Project

Project/Area Number 06402062
Research Category

Grant-in-Aid for General Scientific Research (A)

Allocation TypeSingle-year Grants
Research Field Natural disaster science
Research InstitutionTOHOKU UNIVERSITY

Principal Investigator

HIRASAWA Tomowo  Tohoku Univ., Fac. of Sci. Prof., 理学部, 教授 (80011568)

Co-Investigator(Kenkyū-buntansha) SATO Takashi  Geological Survey J.Senior Scientist, 主任研究官
KATO Naoyuki  Tohoku Univ., Fac. of Sci. Res. Ass., 理学部, 助手 (60224523)
YAMAMOTO Kiyohiko  Tohoku Univ., Fac. of Sci. Ass. Prof., 理学部, 助教授 (90004390)
Project Period (FY) 1994 – 1995
Project Status Completed (Fiscal Year 1995)
Budget Amount *help
¥13,600,000 (Direct Cost: ¥13,600,000)
Fiscal Year 1995: ¥5,600,000 (Direct Cost: ¥5,600,000)
Fiscal Year 1994: ¥8,000,000 (Direct Cost: ¥8,000,000)
KeywordsStick-Slip / Stable Sliding / Asperity / Brittle Fracture / Microfracture / 不安定すべり / 時間依存性
Research Abstract

A stick-slip experiment is performed on a rock specimen with a pre-existing artificial fault to observe near-fault high-frequency elastic waves generated by stick-slip motion. The main results are as follows : 1) The observed near-fault high-frequency strong-motion duration is approximately proportional to the local breakdown time. 2) The highest peak acceleration observed amounts to a few tens of km/s^2, which is considered to correspond to about 1000gal in the case of natural earthquakes, when the differences is size and frequency are taken into account. Further we model the dynamic behavior of stick-slip motion observed in our laboratory experiment : A number of asperities circular in shape are assumed to distribute on a given fault surface. Each asperity on the fault is to be ruptured after the arrival of the macroscopic rupture front. We consider, however, that there exists some time lag between the arrival time of rupture front and the rupture initiation of the asperity. It is assumed that the time lags for individual asperities obey a certain probability density function. The synthesized strong motions reproduce well the characteristics of the observed strong motions.
The above result based on the model implies that high-frequency strong motions observed during unstable sliding on a pre-existing fault are generated mainly by brittle fracture of asperities on the fault surfaces. It follows from this that acoustic emission (AE) due to brittle fracture of asperities should be observed even in the case of macroscopically stable sliding on a pre-existing fault. To examine this, an experiment of stable sliding is performed on a rock specimen with a pre-existing fault. A number of AEs are observed during macroscopically stable sliding to confirm our theoretical expectation. It is further found that the number of AEs per unit slip distance and the average magnitude of AEs are decreased with an increase in macroscopic sliding-speed.

Report

(3 results)
  • 1995 Annual Research Report   Final Research Report Summary
  • 1994 Annual Research Report
  • Research Products

    (10 results)

All Other

All Publications (10 results)

  • [Publications] 加藤 尚之: "microfracture processes in the breakdown zone during dynamic shear rupture inferred from laboratory observation of near-fault higt-frequency strong motion" Pure Appl. Geophys.142. 713-734 (1994)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1995 Final Research Report Summary
  • [Publications] 加藤 尚之: "Dynamics of microfracture processes in the breakdown zone" Adv. in Math. Seismology, Seis. Ress, Beijing. 128-147 (1995)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1995 Final Research Report Summary
  • [Publications] 西澤 修: "跳躍現象から推定される断層近傍での強いゆれ" 地質ニュース. 491. 9-16 (1995)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1995 Final Research Report Summary
  • [Publications] Kato, N., K.Yamamoto and T.Hirasawa: "Microfracture processes in the breakdown zone during dynamic shear rupture inferred from laboratory bservation of near-fault high-frequency strong motion." Pure Appl. Geophys.Vol. 142. 713-734 (1994)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1995 Final Research Report Summary
  • [Publications] Kato, N.and T.Hirasawa: "Dynamics of microfracture processes in the breakdown zone." Adv. in Math. Seismology, Seism. Press, Beijing. 128-147 (1995)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1995 Final Research Report Summary
  • [Publications] Nishizawa, O., T.Sato and M.Sugihara: "Strong ground motion near an earthquake fault inferred from upthrow of objects." Chishitsu News. No. 491. 9-16 (1995)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1995 Final Research Report Summary
  • [Publications] 加藤尚之: "Microfracture processes in the breakdown zone during dynamic shear rupture inferred from laboratory observation of near-fault high-frequency strong motion" Pure Appl.Geophys.142. 713-734 (1994)

    • Related Report
      1995 Annual Research Report
  • [Publications] 加藤尚之: "Dynamics of microfracture processes in the breakdown zone" Adv.in Math.Seismology,Seis.Press,Beijing. 128-147 (1995)

    • Related Report
      1995 Annual Research Report
  • [Publications] 西澤修: "跳躍現象から推定される断層近傍での強いゆれ" 地質ニュース. 491. 9-16 (1995)

    • Related Report
      1995 Annual Research Report
  • [Publications] 加藤尚之: "Microfracture processes in the breakdown zone during dynamic shear rupture inferred from laboratory observation of near-fault high-frequency strong motion" Pure Appl.Geophys.142. 713-734 (1994)

    • Related Report
      1994 Annual Research Report

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Published: 1994-04-01   Modified: 2016-04-21  

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