Study on the regionality of earthquake Source spectra

地震震源谱的区域性研究

• 批准号: 04640394
• 负责人: OHTAKE Masakazu
• 金额: $ 1.09万
• 依托单位: TOHOKU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1993
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04640394/
• 关键词: seismic wave; source spectrum; stress drop; attenuation; scattering; site effect; 火山フロント; 地盤の増巾特性; スペクトル

For assessing the regionality of earthquake source spectra, we analized waveforms of micro- to small-sized earthquakes ocurring in different regions in Japan. One of the most important results is the finding of systematic difference in stress drop for shallow earthquakes occurring in the aftershock region of the 1984 Naganoken-Seibu earthquake (M=6.8) and in the Asio region where stationary seismic activity is observed. Detailed analysis of waveforms revealed that the ratio of P to S wave attenuation is higher than unity in contrast to past studies. We also revealed that site amplification effect is not negligible even at hard-rock observatiion sites for high-frequency seismic waves. We further attempted to separate the effects of seismic wave dissipation due to intrinsic attenuation and scattering, based on the theoretical formulation of scattering behavior that was done in this study. The theoretical work includes formulation of analitic solutions of the two-dimensional multiple isotropic scattering, and seismogram envelope synthetics including P-S conversions.The broad-band seismometer that was newly installed by this study is in full operation, and the observation is to be continued. The high quality date from this observation will largely contribute to extend our study to larger earthquakes.

为了评价震源谱的区域性，我们分析了发生在日本不同地区的中小地震波形。其中最重要的结果之一是发现了1984年长野县-西武地震（M=6.8）余震区和观测到稳定地震活动的Asio地区发生的浅源地震的应力降的系统差异。详细的波形分析表明，P波和S波的衰减比大于1，与以往的研究相反。本文还揭示了即使在硬岩高频地震波观测场地，场地放大效应也是不可忽略的。我们进一步尝试分离地震波耗散的影响，由于固有的衰减和散射，在本研究中完成的散射行为的理论公式的基础上。理论工作包括二维多次波各向同性散射的解析解的推导和包含P-S转换的地震图包络合成。这次观测的高质量数据将在很大程度上有助于将我们的研究扩展到更大的地震。

项目成果

Fukushima,Y.,et al.: "Measurement of Q^<-1> for S waves in Mudstone at Chikura,Japan:Comparison of incident and reflected phases" Bull.Seismol.Soc.Amer.82. 148-163 (1992)

Fukushima,Y.,et al.：“日本 Chikura 泥岩中 S 波的 Q^<-1> 测量：入射相位和反射相位的比较”Bull.Seismol.Soc.Amer.82。

Ohtake,M.: "Derivation of the three-parameter model of frequency distribution of earthquake magnitude" Tohoku Geophys.J.34. 115-119 (1993)

Ohtake，M.：“地震震级频率分布三参数模型的推导”东北地球物理学.J.34。

Yoshimoto,K.,et al.: "Frequency dependent attenuation of P and S waves in the Kanto area,Japan,based on the coda normalizaction method" Geophys.J.Internat.110. (1993)

Yoshimoto,K.,et al.：“日本关东地区 P 波和 S 波的频率相关衰减，基于尾声归一化方法”Geophys.J.Internat.110。

Sato,H.: "Energy transport in one- and two-dimensional scattering media:Analytic solutions of the multiple isotropic scattering media" Geophys.J.Int.112. 141-146 (1993)

Sato, H.：“一维和二维散射介质中的能量传输：多种各向同性散射介质的解析解”Geophys.J.Int.112。

Yoshimoto,K.,H,Sato and M.Ohtake: "Frequency dependent attenuation of P and S waves in the Kanto area,Japan,based on the coda mormalization method" Geophys.J.Int.114. 165-174 (1993)

Yoshimoto,K.,H,Sato 和 M.Ohtake：“日本关东地区 P 波和 S 波的频率相关衰减，基于尾声标准化方法”Geophys.J.Int.114。