Seismic amplitude tomography for crustal attenuation beneath China
Seismic amplitude tomography for crustal attenuation beneath China
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DOI：
10.1111/j.1365-246x.2008.03776.x
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发表时间：
2008-07
影响因子：
2.8
通讯作者：
T. Hearn;Su-Long Wang;S. Pei;Zhong-huai Xu;J. Ni;Yan-xiang Yu
中科院分区：
文献类型：
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作者：
T. Hearn;Su-Long Wang;S. Pei;Zhong-huai Xu;J. Ni;Yan-xiang Yu
振幅层析成像直接从记录的波振幅重建地震衰减。我们已将层析成像应用于《中国地震年报》中的振幅数据，并从构造角度解释了地壳衰减的区域性变化。地震振幅最初是为了确定ML和MS震级而记录的。它们一般对应于短周期S波和中周期瑞利波水平分量的最大振幅。这两套测量对地壳结构都很敏感。从M-L振幅的峰值振幅传播球形与显着的色散和散射。MS振幅表现为圆柱形扩展，几乎没有色散。平均地壳Q值衰减在1赫兹是737和505，分别为ML和MS，有很大的区域变化。衰减中的频率依赖性也被指示。衰减最低（高Q值）的区域是华南地块、四川盆地、鄂尔多斯地台、大兴安岭和朝鲜半岛。这些地区往往是构造活动不活跃的地区，通常由上地壳的侵入岩和碎屑岩控制。衰减最高（低Q值）的区域位于渤海盆地、云南、松潘-甘孜地体东部、鄂尔多斯台地边缘和祁连山。这些主要是活动盆地、地堑和褶皱带。大陆边缘也高度衰减S波和表面波。
SUMMARY Amplitude tomography reconstructs seismic attenuation directly from recorded wave amplitudes. We have applied the tomography to amplitude data reported in the ‘Annual Bulletin of Chinese Earthquakes’ and interpreted the regionally varying crustal attenuation in terms of tectonics. The seismic amplitudes were originally recorded for determining the M L and M S magnitudes. They generally correspond to the maximum amplitudes of the horizontal components of the short-period S waves and intermediate-period Rayleigh waves. Both sets of measurements are sensitive to crustal structure. The peak amplitudes from M L amplitudes spread spherically with significant dispersion and scattering. M S amplitudes show cylindrical spreading with little dispersion. Average crustal Q values for attenuation at 1 Hz are 737 and 505 for M L and M S, respectively, with substantial regional variations. Frequency dependence in the attenuation is also indicated. Regions with the lowest attenuation (high Q values) are beneath the south China Block, Sichuan Basin, Ordos Platform, the Daxinganling and the Korea Craton. These tend to be tectonically inactive regions, which are generally dominated by intrusive and cratonic rocks in the upper crust. Regions with the highest attenuation (low Q values) are beneath Bohai Basin, Yunnan, eastern Songpan-Ganzi Terrain, margins of the Ordos platform and the Qilian Shan. These are predominantly active basins, grabens and fold belts. The continental margin also highly attenuates both S and surface waves.