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由余震层析成像给出了2010年4月14日玉树MS7.1地震震中附近上地壳的高分辨率二维(水平)地震波速度模型。这个速度模型是使用包括台站校正和地震深度校正在内的与Pn层析成像类似的方法得到的。最显著的结果是在玉树—甘孜断裂带(YGF)的震中位置处存在快速异常区。主破裂起始于这一快速异常区并向东南传播至玉树的慢速异常区。2010年5月29日邻近断层上的第二大余震也发生在这一快速异常区。这些结果以明显的例子表明,上地壳中地震波速度结构的横向变化控制着2010年玉树地震的发生原因(应力积累)和破裂传播以及余震分布。本文给出的简单二维Pg波走时层析成像方法介绍了一种利用丰富余震数据研究大地震破裂过程的新方法。
By aftershock tomography, a high-resolution two-dimensional (horizontal) seismic velocity model of the upper crust near the epicenter of the Yushu MS7.1 earthquake on April 14, 2010 is given. This velocity model is obtained using a similar method to Pn tomography, including station correction and seismic depth correction. The most notable result is the rapid anomaly at the epicenter of Yushu-Garze fracture zone (YGF). The main rupture begins in this rapidly anomalous zone and propagates southeast to the slow anomalous zone of Yushu. The second major aftershock on the adjacent fault occurred on May 29, 2010 in this fast anomaly. These results show, as obvious examples, that lateral changes in the velocity structure of seismic waves in the upper crust control the causes of the 2010 Yushu earthquake (stress accumulation) and propagation of fractures and aftershocks. A simple two-dimensional Pg wave traveltime tomography method presented in this paper introduces a new method to study the rupture process of large earthquakes using rich aftershocks data.