Frequency-difference backprojection of earthquakes
Frequency-difference backprojection of earthquakes
复制标题
地震频差反投影
DOI：
10.1093/gji/ggac323
复制
发表时间：
2022
影响因子：
2.8
通讯作者：
Dowling, David
中科院分区：
文献类型：
--
作者：
Neo, Jing Ci;Fan, Wenyuan;Huang, Yihe;Dowling, David
反投影已被证明是有用的成像大地震破裂过程。该方法通常是鲁棒的，并且需要关于断层几何形状或地球速度模型的相对简单的假设。它可以应用于时域和频域。反投影图像通常从在窄频带中过滤的记录中获得，限制了其揭示整个破裂过程的能力。在这里，我们开发和应用一种新的频差反投影（FDBP）技术来成像大地震，它模仿低于信号带宽的频率。新方法起源于频率差波束形成，其最初被设计用于定位声源。我们的方法叠加的相位差的频率对，给出的autofproduct，并从3-D地球结构的散射和实时误差的影响较小。它可以更准确地定位源，尽管分辨率较低。在这项研究中，我们首先开发的FDBP算法，然后通过执行合成测试验证它。我们进一步比较了FDBP方法的两种叠加技术，带宽平均自积和它的对应物（BWAP和非BWAP），以及它们在反投影图像中的效果。然后，我们应用FDBP和传统的反投影方法，2015年M7.8廓尔喀地震作为一个案例研究。两种方法的反投影结果吻合较好，发现FDBP非BWAP快照的峰值辐射轨迹在破裂过程中的标准误差小于0.33°。FDBP方法在解决复杂构造地区复杂地震破裂过程中显示出良好的前景。
Backprojection has proven useful in imaging large earthquake rupture processes. The method is generally robust and requires relatively simple assumptions about the fault geometry or the Earth velocity model. It can be applied in both the time and frequency domain. Backprojection images are often obtained from records filtered in a narrow frequency band, limiting its ability to uncover the whole rupture process. Here, we develop and apply a novel frequency-difference backprojection (FDBP) technique to image large earthquakes, which imitates frequencies below the bandwidth of the signal. The new approach originates from frequency-difference beamforming, which was initially designed to locate acoustic sources. Our method stacks the phase-difference of frequency pairs, given by the autoproduct, and is less affected by scattering and -time errors from 3-D Earth structures. It can potentially locate sources more accurately, albeit with lower resolution. In this study, we first develop the FDBP algorithm and then validate it by performing synthetic tests. We further compare two stacking techniques of the FDBP method, Band Width Averaged Autoproduct and its counterpart (BWAP and non-BWAP), and their effects in the backprojection images. We then apply both the FDBP and conventional backprojection methods to the 2015M7.8 Gorkha earthquake as a case study. The backprojection results from the two methods agree well with each other, and we find that the peak radiation loci of the FDBP non-BWAP snapshots have standard error of less than 0.33° during the rupture process. The FDBP method shows promise in resolving complex earthquake rupture processes in tectonically complex regions.