Determination of earthquake focal depths and source time functions in central Asia using teleseismic P waveforms
Determination of earthquake focal depths and source time functions in central Asia using teleseismic P waveforms
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DOI：
10.1029/2009gl039494
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发表时间：
2009-09
影响因子：
5.2
通讯作者：
R. Chu;Lupei Zhu;D. Helmberger
中科院分区：
文献类型：
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作者：
R. Chu;Lupei Zhu;D. Helmberger
我们发展了一种确定震源时间函数和震源深度的新方法。它使用理论上的绿色函数和具有正性约束的时域反褶积来估计来自地震P波形的源时间函数。在此过程中，还利用直接P相和深度相的时间间隔确定了地震的震源深度。我们将这种方法应用于1990年至2005年期间在中亚发生的606次地震。结果表明，质心矩张量解（通常使用非常长周期的体波和面波计算全球大于M5.0的地震）系统地高估了震源深度和持续时间，特别是对于浅层事件。远离俯冲带，606次地震中的大多数发生在地壳顶部20公里内。地震的这种浅层分布表明，该地区的地热较高，下地壳韧性较弱。
We developed a new method to determine earthquake source time functions and focal depths. It uses theoretical Green's function and a time‐domain deconvolution with positivity constraint to estimate the source time function from the teleseismic P waveforms. The earthquake focal depth is also determined in the process by using the time separations of the direct P and depth phases. We applied this method to 606 earthquakes between 1990 and 2005 in Central Asia. The results show that the Centroid Moment Tensor solutions, which are routinely computed for earthquake larger than M5.0 globally using very long period body and surface waves, systematically over‐estimated the source depths and durations, especially for shallow events. Away from the subduction zone, most of the 606 earthquakes occurred within the top 20 km of crust. This shallow distribution of earthquakes suggests a high geotherm and a weak ductile lower crust in the region.