Shear wave Q structure and its lateral variation in the crust of China and surrounding regions
Shear wave Q structure and its lateral variation in the crust of China and surrounding regions
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DOI：
10.1111/j.1365-246x.2004.02196.x
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发表时间：
2004-04
影响因子：
2.8
通讯作者：
A. Jemberie;B. Mitchell
中科院分区：
文献类型：
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作者：
A. Jemberie;B. Mitchell
我们利用单站多模式方法获得了中国及周边地区几种面波路径的三层地壳剪切波模型Q（Qμ），并将根据已知震源深度和机制计算的基模和高阶瑞利波振幅谱与实测谱进行了比较。这三层厚度约为60公里，大致构成了青藏高原的整个地壳，也包括地壳较薄地区的地壳和部分上地幔。最浅层（10 km厚）的Qμ值在青藏高原西部最低（约40），在中国东南部最高（约250）。中层10-30 km深度，Qμ值最低（60-80）在西藏和帕米尔冲断系附近，最高（120-140）在中国中部和中朝地台部分地区。最深层（30-60 km）的Qμ的不均匀性远大于上两层，但现有的结果表明，帕米尔逆冲断层系下的Qμ最低（约80），蒙古南部最高（约180）。虽然在某些地区，事件和台站覆盖的密度不够，但我们可以绘制出大陆地壳Qμ变化的第一张区域化图。深度范围为0-10公里和10-30公里的地图，一般显示出良好的协议与其他阶段的早期获得的Q结果和良好的相关性与该活动区的构造。
SUMMARY We have obtained three-layer crustal models of shear wave Q (Qμ) for several surface wave paths in China and peripheral regions using a single-station, multimode method in which amplitude spectra of fundamental-mode and higher-mode Rayleigh waves, computed for known source depths and mechanisms, are compared to measured spectra. The three layers, totaling 60 km in thickness, roughly comprise the entire crust in the Tibetan plateau and include both the crust and part of the uppermost mantle in other regions where the crust is thinner. Qμ in the shallowest layer, 10 km thick, is lowest (about 40) in the western portion of the Tibetan plateau and highest (about 250) in southeastern China. In the middle layer, at 10–30 km depth, Qμ is lowest (60–80) beneath Tibet and the Pamir thrust system and highest (120–140) in central China and parts of the Sino-Korean platform. Uncertainties of Qμ in the deepest layer, at 30–60 km depth, are much greater than in the upper two layers but available results suggest that Qμ is lowest (about 80) under the Pamir thrust system and highest (about 180) under southern Mongolia. The densities of event and station coverage, although wanting in some regions, allow us to develop the first regionalized maps of crustal Qμ variation for continents. The maps, for depth ranges 0–10 km and 10–30 km, generally show good agreement with Q results obtained earlier with other phases and good correlation with the tectonics of this active region.