Rupture imaging of the Mw 7.9 12 May 2008 Wenchuan earthquake from back projection of teleseismic P waves
Rupture imaging of the Mw 7.9 12 May 2008 Wenchuan earthquake from back projection of teleseismic P waves
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DOI：
10.1029/2008gc002335
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发表时间：
2009-04
期刊：
影响因子：
3.7
通讯作者：
Yan Xu;K. Koper;Oner Sufri;Lupei Zhu;A. Hutko
中科院分区：
文献类型：
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作者：
Yan Xu;K. Koper;Oner Sufri;Lupei Zhu;A. Hutko
2008年5月12日的汶川7.9级地震是自1976年唐山地震以来中国破坏性最大的地震。数万人死亡，数十万人受伤，数百万人无家可归。本文利用多组地震仪阵列的远震P能反向投射，推断了汶川地震的详细破裂过程。这项技术直到最近才变得可行，并且可能比传统的远震体波有限断层反演更快；因此，它可以减少通知应急响应机构的时间。利用IRIS DMC，我们在震中30-95°处采集了255个垂直分量的宽带P波。我们发现，在5秒或更大的周期，几乎所有这些P波都是相干的，足以用于全球阵列。我们采用了一个简单的下采样启发式方法来定义一个由70个站点组成的全局子阵列，以减少阵列响应函数（ARF）的不对称性和副瓣。我们还考虑了阿拉斯加、澳大利亚和欧洲的三个区域地震仪子阵列，它们的孔径小于30°，P波的相干周期短至15秒。这些子阵列的单个arf向子阵列倾斜；然而，区域子阵波束在1秒时的线性和产生了对称的ARF，类似于在5秒时修饰的全局子阵。对于这两种配置，我们获得了相同的破裂方向，破裂长度和破裂时间。研究发现，汶川地震在震源时间后0、23、57 s有3个明显的高波束功率脉冲，其中23 s的脉冲最高，向东北方向单向破裂约300 km 110 s，平均速度为2.8 km/s。利用相对稀疏的全球地震仪网络，例如美国地质调查局用于近实时定位地震的地震仪网络，有可能在震源时间20-30分钟内确定未来的大倾滑地震的类似结果。
The Mw 7.9 Wenchuan earthquake of 12 May 2008 was the most destructive Chinese earthquake since the 1976 Tangshan event. Tens of thousands of people were killed, hundreds of thousands were injured, and millions were left homeless. Here we infer the detailed rupture process of the Wenchuan earthquake by back‐projecting teleseismic P energy from several arrays of seismometers. This technique has only recently become feasible and is potentially faster than traditional finite‐fault inversion of teleseismic body waves; therefore, it may reduce the notification time to emergency response agencies. Using the IRIS DMC, we collected 255 vertical component broadband P waves at 30–95° from the epicenter. We found that at periods of 5 s and greater, nearly all of these P waves were coherent enough to be used in a global array. We applied a simple down‐sampling heuristic to define a global subarray of 70 stations that reduced the asymmetry and sidelobes of the array response function (ARF). We also considered three regional subarrays of seismometers in Alaska, Australia, and Europe that had apertures less than 30° and P waves that were coherent to periods as short as 1 s. Individual ARFs for these subarrays were skewed toward the subarrays; however, the linear sum of the regional subarray beams at 1 s produced a symmetric ARF, similar to that of the groomed global subarray at 5 s. For both configurations we obtained the same rupture direction, rupture length, and rupture time. We found that the Wenchuan earthquake had three distinct pulses of high beam power at 0, 23, and 57 s after the origin time, with the pulse at 23 s being highest, and that it ruptured unilaterally to the northeast for about 300 km and 110 s, with an average speed of 2.8 km/s. It is possible that similar results can be determined for future large dip‐slip earthquakes within 20–30 min of the origin time using relatively sparse global networks of seismometers such as those the USGS uses to locate earthquakes in near–real time.