Crustal structure of China and surrounding regions from P wave traveltime tomography
Crustal structure of China and surrounding regions from P wave traveltime tomography
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DOI：
10.1029/2005jb003962
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发表时间：
2006-03
影响因子：
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通讯作者：
Youshun Sun;M. Toksöz
中科院分区：
文献类型：
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作者：
Youshun Sun;M. Toksöz
[1]本文利用从《中国地震年刊》（ABCE）中提取的50万条高质量P波初至资料，应用Zhao等的层析成像方法，建立了中国及周边地区地壳和上地幔的三维P波速度模型。这种层析成像方法除了平滑速度变化外，还可以适应莫霍面等速度不连续性。水平方向的空间分辨率为1° × 1°，深度为10公里。上地壳速度图像与盆地、青藏高原等地表地质特征有较好的对应关系。在前寒武纪地区（塔里木盆地、鄂尔多斯盆地、四川盆地和松辽盆地西半部）的下地壳中发现了高速异常。最高速度异常位于四川盆地下方。渤海湾下成像的高、低速异常与一个主要的新生代裂谷系统的存在有关。在华南陆块下地壳，P波速度北低南低。由于火山作用，印支地块的地壳和上地幔速度都很低。青藏高原地区的Pn速度高于其它地区，这主要是由于地壳较厚。层析成像模型显著降低了走时残差。通过重新定位大型爆炸和地震进行的试验验证了三维速度模型。
[1] A three-dimensional (3-D) P wave velocity model is developed for the crust and uppermost mantle of China and the surrounding area by applying the tomography method of Zhao et al. using 500,000 high-quality P wave first arrivals extracted from the Annual Bulletin of Chinese Earthquakes (ABCE). This tomographic method can accommodate velocity discontinuities such as the Moho in addition to smooth velocity variations. The spatial resolution is 1° × 1° in the horizontal direction and 10 km in depth. The velocity images of the upper crust correspond well with the surface geologic features such as basins and the Tibetan Plateau. High-velocity anomalies are found in the lower crust beneath the Precambrian regions (Tarim Basin, Ordos Basin, Sichuan Basin, and western half of Songliao Basin). The highest-velocity anomaly is beneath the Sichuan Basin. High- and low-velocity anomalies imaged beneath the Bohai Gulf are associated with the presence of a major Cenozoic rift system. In the lower crust beneath the South China Block, P wave velocities are lower in the north than in the south. The Indochina Block shows low velocities both in the crust and in the uppermost mantle due to volcanism. The Pn velocities in the Tibet area are higher than those in other areas largely due to thicker crust. Tomographic model significantly reduces the traveltime residuals. Tests conducted by relocating large explosions and earthquakes validate the 3-D velocity model.