強震動を対象とした海溝型巨大地震の震源モデルをより単純化する試み : 疑似点震源モデルによる2011年東北地方太平洋沖地震の強震動シミュレーション  [in Japanese] A Simplified Source Model to Explain Strong Ground Motions from a Huge Subduction Earthquake : Simulation of Strong Ground Motions for the 2011 off the Pacific Coast of Tohoku Earthquake with a Pseudo Point-source Model  [in Japanese]

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Author(s)

    • 野津 厚 NOZU Atsushi
    • 独立行政法人港湾空港技術研究所 Independent Administrative Institution, Port and Airport Research Institute

Abstract

A new simplified source model is proposed to explain strong ground motions from a huge subduction earthquake. The proposed model is simpler, and involves less model parameters, than the conventional characterized source model, which itself is a simplified expression of actual earthquake source. In the proposed model, the spacio-temporal distribution of slip within a subevent is not modeled. Instead, the source spectrum associated with the rupture of a subevent is modeled and it is assumed to follow the omega-square model. By multiplying the source spectrum with the path effect and the site amplification factor, the Fourier amplitude at a target site can be obtained. Then, combining it with Fourier phase characteristics of a smaller event, the time history of strong ground motions from the subevent can be calculated. Finally, by summing up contributions from the subevents, strong ground motions from the entire rupture can be obtained. The source model consists of six parameters for each subevent, namely, longitude, latitude, depth, rupture time, seismic moment and corner frequency of the subevent. Finite size of the subevent can be taken into account in the model, because the corner frequency of the subevent is included in the model, which is inversely proportional to the length of the subevent. Thus, the proposed model is referred to as the "pseudo point-source model". To examine the applicability of the model, a pseudo point-source model was developed for the 2011 off the Pacific coast of Tohoku earthquake. The model comprises nine subevents, located off Miyagi Prefecture through Ibaraki Prefecture. The velocity waveforms (0.2-1 Hz) and the Fourier spectra (0.2-10 Hz) at 15 sites calculated with the pseudo point-source model agree well with the observed ones, indicating the applicability of the model. Then the results were compared with the results of a super-asperity model of the same earthquake, which can be considered as an example of characterized source models. Although the pseudo point-source model involves much less model parameters than the super-asperity model, the errors associated with the former model were comparable to those for the latter model for velocity waveforms. Furthermore, the errors associated with the former model were much smaller than those for the latter model for Fourier spectra. These evidences indicate the usefulness of the pseudo point-source model.

Journal

  • Zisin (Journal of the Seismological Society of Japan. 2nd ser.)

    Zisin (Journal of the Seismological Society of Japan. 2nd ser.) 65(1), 45-67, 2012-09-28

    SEISMOLOGICAL SOCIETY OF JAPAN

References:  45

Codes

  • NII Article ID (NAID)
    10031122852
  • NII NACSIS-CAT ID (NCID)
    AN00305741
  • Text Lang
    JPN
  • Article Type
    ART
  • ISSN
    00371114
  • NDL Article ID
    024213948
  • NDL Call No.
    Z15-199
  • Data Source
    CJP  NDL  J-STAGE 
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