SUMMARY

Conventionally, the routine workflow of stress field estimation from seismic data consists of two steps: focal mechanism inversion and stress inversion. This two-step workflow suffers from the cumulative uncertainties of both the focal mechanism inversion process and the stress inversion process. To mitigate the cumulative errors, a few previous studies have put efforts to directly estimate the stress field using P-wave polarities. In this study, we develop a new approach to directly estimate tectonic stress fields with better accuracy through waveform matching. This new approach combines the two steps into a one-step workflow to mitigate the cumulative uncertainties through the physical relationship between a stress field and the recorded waveforms. This method assumes a homogeneous stress field in space in the local source region and that the fault slip occurs in the direction of the resolved shear stress acting on the fault plane. Under these assumptions, the stress pattern that generates the theoretical waveforms that best fit the waveforms observed is directly retrieved as the true stress field. The merits of the new approach include that this approach can mitigate the cumulative uncertainties suffered from the conventional two-step workflow and does not require determination of the focal mechanisms of each event; thus, this method is applicable to data sets with few stations. Synthetic tests with and without noise are conducted to demonstrate the performance and merits of this method. Then, the new approach is applied to a real data set from central Oklahoma between March 2013 and March 2016. The resulting stress pattern is consistent with that estimated from previous studies examining the same region. These applications show the benefits and validity of the new approach.

中文翻译：

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通过波形匹配直接估算应力场

概要

按照惯例，根据地震数据估算应力场的常规工作流程包括两个步骤：震源机制反演和应力反演。这种分两步的工作流程受焦点机制反转过程和应力反转过程的累积不确定性的影响。为了减轻累积误差，一些先前的研究已经进行了努力，以使用P波极性直接估计应力场。在这项研究中，我们开发了一种新方法，可以通过波形匹配直接以更好的精度估算构造应力场。这种新方法将两个步骤组合为一个步骤的工作流程，以通过应力场和记录的波形之间的物理关系来减轻累积的不确定性。该方法假定局部源区域中空间中的应力场均匀，并且断层滑动发生在作用于断层平面上的解析切应力的方向上。在这些假设下，可以将生成最适合观察到的波形的理论波形的应力模式直接检索为真实应力场。新方法的优点包括：该方法可以减轻传统的两步工作流所带来的累积不确定性，并且不需要确定每个事件的焦点机制；因此，该方法适用于站数少的数据集。进行有噪声和无噪声的综合测试，以证明该方法的性能和优点。然后，这项新方法已应用于2013年3月至2016年3月之间俄克拉荷马州中部的真实数据集。由此产生的应力模式与先前研究同一地区的研究估计的一致。这些应用显示了新方法的好处和有效性。