王长在 吴建平 房立华 王未来. 2011: 2009年姚安地震序列定位及震源区三维P波速度结构研究. 地震学报, 33(2): 123-133.
引用本文: 王长在 吴建平 房立华 王未来. 2011: 2009年姚安地震序列定位及震源区三维P波速度结构研究. 地震学报, 33(2): 123-133.

2009年姚安地震序列定位及震源区三维P波速度结构研究

  • 摘要: 利用2009年7月9日姚安MS6.0地震序列的到时数据,应用双差层析成像方法,对地震进行了重定位,并反演了震源区的三维速度结构.经过资料选取,共有873次余震事件参加了反演.重定位结果显示,姚安地震余震序列呈WNW向条带状分布,大部分地震的震源深度集中在3——12 km之间.从余震的深度分布随时间的变化推测,姚安MS6.0地震震源区的应力分布经过3次调整,开始的40个小时,应力从下向上调整;随后的20个小时, 余震散布在3——23 km深度范围内,应力在较大深度范围内调整;从第60个小时之后, 12 km以下的应力调整结束,主要是浅部应力释放.三维速度结构结果表明,姚安主震发生在低速体与高速体的过渡区域,余震主要分布在高低速过渡带及高速体一侧.结合重定位结果, 推测在这一高低速过渡带附近存在隐伏断层,走向大约为N65deg;W.

     

    Abstract: The Yaoan,Yunnan, MS6.0 earthquake occurred on July 9,2009. By inverting seismic phase arrival time data and using the double-difference tomography approach (Zhang and Thurber), the aftershocks were relocated and a 3-D P-wave velocity structure around the earthquake source region were obtained. After data selection 873 aftershocks were used for inversion. The relocation result shows that aftershocks distribute in a belt with WNW-ESE trend. Focal depth of most aftershocks is between3 kmand12 km. By analyzing the change of focal depth with time we infer that the stress in the focal region underwent three time adjustment. The stress was adjusted from bottom to top in the first 40 hours,and then was adjusted in a larger depth range in the following 20 hours. After 60 hours, the stress adjustment stopped below the depth of12 kmand the stress was released mainly in the shallow crust. The obtained 3-D velocity structure indicates that the mainshock occurred in a transition zone between low and high velocity bodies. The aftershocks mainly distribute in the velocity transition zone and by the side of the high velocity body. Combining with the relocation result,we infer that there exists a buried fault with ~N65deg;W strike in the transition zone between low and high velocity anomalies.

     

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