Velocity structure of the uppermost mantle beneath East Asia from Pn tomography and its dynamic implications
Velocity structure of the uppermost mantle beneath East Asia from Pn tomography and its dynamic implications
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DOI：
10.1002/jgrb.50085
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发表时间：
2013-01
期刊：
影响因子：
--
通讯作者：
Su-Long Wang;F. Niu;Guo-Min Zhang
中科院分区：
文献类型：
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作者：
Su-Long Wang;F. Niu;Guo-Min Zhang
由于印度板块的碰撞以及太平洋板块和菲律宾板块的俯冲所引起的吸力，东亚是地球表面构造活动最活跃的地区之一。为了更好地了解该地区复杂的形变和活跃的地震活动，我们进行了Pn走时层析成像，以估计东亚最上地幔的压缩波速度。我们收集了东经60° ~ 145°E、北纬15° ~ 60°N的矩形区域内1354个台站记录的27,777次地震的296,334个Pn波至。在检查了目录中潜在的系统性偏差后，从三个不同的目录中仔细整合了数据集。反演结果显示，研究区域存在大规模的速度扰动。108°E以西的Pn速度比东部高约10%。在每个区域中，稳定块体往往具有高Pn速度，而边界区域，这表明了一个高水平的地震活动和地表变形，出现了低Pn速度。我们进一步计算了这两个区域的Benioff应变率，发现它与平均Pn速度负相关。我们的观测结果表明，Pn速度主要由莫霍面温度决定，是岩石圈强度的一个很好的指标。
East Asia is one of the most tectonically active regions on Earth's surface due to the collision from the India plate and the suctions induced by the subduction of the Pacific and Philippine plates. To better understand the complicated deformation and active seismicity of the area, we conducted a Pn traveltime tomography to estimate the compressive wave speed of the uppermost mantle beneath East Asia. We collected a total of 296,334 Pn arrivals recorded by 1354 stations from 27,777 earthquakes in a rectangular area from 60°E to 145°E in longitude, 15°N to 60°N in latitude. The data set was carefully integrated from three different catalogs after examining potential systematic biases in the catalogs. The inversion results revealed a large‐scale velocity perturbation in the study area. Pn velocity in the region west to ~108°E is approximately 10% higher than that in the east. In each region, stable blocks tend to have high Pn velocity while the boundary regions, which show a high level of seismicity and surface deformation, appear to have low Pn velocity. We further computed the Benioff strain rate in the two regions and found it correlates negatively with the averaged Pn velocity. Our observations here suggest that Pn velocity, which is predominantly determined by Moho temperature, is a good indicator of lithosphere strength.