断層近傍の強震動パルスの成因

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書誌事項

タイトル別名
  • Generation Mechanism of Strong Ground Motion Pulse Near the Earthquake Fault
  • ダンソウ キンボウ ノ キョウシンドウ パルス ノ セイイン

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抄録

Strong pulse-like ground motion has been often observed during the earthquake near the fault, and considered to cause severe damage. In the present paper, the physical mechanism for strong pulse near the fault is investigated. Ground velocity waveform near the fault is calculated using the nearfield displacement waveform expressions generated from slip on the fault [AKI and RICHARDS (1980)] assuming slip rate time function to be a slightly modified Kostrov's type time function that has a linearly increasing initial part with duration of Td simulating the effect of slip weakening frictional model. We found that the nearfield and intermediate terms are canceled out, and the farfield term is predominant in ground velocity waveform near the fault. The strong pulse in velocity waveform is generated mainly by the rupture propagation of an equivalent line source and slip acceleration on the fault. If Td is short enough and the slip velocity function is impulsive, the strong pulse near the fault is generated mainly by the rupture propagation effect and the pulse width is expressed as L(1/ν-1/β), where L is the length of the equivalent line source, i. e., the line segment inside the fault which connects from the initial point of rupture to the observer, and ν is the rupture velocity, and β is the shear wave velocity. When Td becomes longer corresponding to the faulting process for large critical displacement of slip weakening friction law, the pulse width becomes longer than L(1/ν-1/β).

収録刊行物

  • 地震　第２輯

    地震　第２輯 51 (2), 161-170, 1998

    公益社団法人 日本地震学会

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