Attenuation of S Waves and Coda Waves in the Inner Zone of Southwestern Japan

• KANAO, Masaki

• ITO, Kiyoshi

抄録

The attenuation properties of S and coda waves were studied in the northern Kinki district by analyzing local earthquakes, recorded at 21 stations of the Tottori, Abuyama and Hokuriku micro-earthquake observatories, Kyoto University. The data consist of four datasets of shallow events in the crust, and deep events in the upper mantle which occurred near Wakayama and Nagoya. Quality factors of S waves (Q_s) were determined by the maximum RMS amplitude ratio method, and by the single station method. The decay of the maximum amplitudes of S waves with distances was analyzed within the hypocentral distance range of 50～250km at five frequencies of 2, 4, 8, 16 and 32Hz for the transverse component seismograms. Quality factors of coda waves (Q_c) were also determined for the same data on the basis of the single scattering model of coda generation in the same frequency range. The result of Q_s by the maximum RMS amplitude ratio method and Q_c for local earthquakes are considered to be reliable. Q_s and Q_c approximately agree with each other within their standard deviations. The values are, for example, about 600 at 8Hz. Therefore, the attenuation properties of S waves and their coda parts are considered to be almost the same in this district. The frequency dependence of Q_s also agrees well with that of Q_c for the datasets in this analysis. The exponent of frequency n, in the formula Q=Q_0 f^n, has values of 0.5～1.1, which are the typical values in the seismic active regions such as island arcs. Q_s indicates regional variations more clearly than Q_c. Q_s values derived from the deep events near Wakayama are larger than those from the other events. This suggests that the attenuation is smaller in the upper mantle in the southern Kinki district relating to the subduction of the Philippine Sea plate.

収録刊行物

• Bulletin of the Disaster Prevention Research Institute

  Bulletin of the Disaster Prevention Research Institute 41 (2), 87-107, 1991-06

  Disaster Prevention Research Institute, Kyoto University

詳細情報

• CRID: 1050001201694503040
• NII論文ID: 120002398934
• NII書誌ID: AA00581033
• ISSN: 04547675
• HANDLE: 2433/124977
• 本文言語コード: en
• 資料種別: departmental bulletin paper
• データソース種別:
  • IRDB
  • CiNii Articles