Seismic anisotropy in the lowermost mantle beneath the Pacific
Seismic anisotropy in the lowermost mantle beneath the Pacific
复制标题
太平洋下地幔下层的地震各向异性
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
H. Benz
中科院分区：
文献类型：
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作者：
J. Ritsema;T. Lay;E. Garnero;H. Benz
在距离85° ~ 120°的宽频带S波的横向分量（SSH）和纵向分量（SSV）之间观测到了长达3 s的起始时间差。经上地幔各向异性校正后，SSH的分裂在100° ~ 120°范围内随距离的增加而增大。数据产生了两种可能的各向异性模型：（1）各向异性可能横向变化，横向各向同性存在于东北太平洋下方高于平均剪切速度的区域，或（2）各向异性可能随深度变化，横向各向同性集中在D”底部的薄（100 km）热边界层中。在距离小于105°的一些记录表明，SSV比SSH更早到达，这表明一般的各向异性可能存在于D”的较浅区域。
Onset time differences of up to 3 s are observed between transverse (SSH) and longitudinal (SSV) components of broadband S waves at distances of 85° to 120° for paths traversing the lowermost mantle (D”) beneath the Pacific. After correction for upper mantle anisotropy, SSH usually arrives earlier than SSV with the splitting increasing with distance from 100° to 120°. The data yield two possible models of anisotropy: (1) anisotropy may vary laterally, with transverse isotropy existing in higher‐than‐average shear velocity regions beneath the northeastern Pacific, or (2) anisotropy may vary with depth, with transverse isotropy concentrated in a thin (100 km) thermal boundary layer at the base of D”. A few recordings at distances less than 105° show that SSV arrives earlier than SSH, indicating that general anisotropy likely exists in shallower regions of D”.