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Acoustic Emission Events Interpreted in Terms of Source Directivity
Pure and Applied Geophysics ( IF 2 ) Pub Date : 2020-06-08 , DOI: 10.1007/s00024-020-02517-w
Petr Kolář , Matěj Petružálek , Tomáš Lokajíček , Jan Šílený , Zuzana Jechumtálová , Petra Adamová , Alena Boušková

During inversion for the source mechanisms of laboratory acoustic emission events, relatively high misfit values (expressed as the RMS of the inverted equations) were observed. Our experiment was performed on Westerly Granite. A processed set of data consisting of 2405 acoustic emission events was used and a semi-homogeneous velocity model was considered. A correction for sensor radiation patterns and individual sensor constants was taken into account, and an acausal attenuation model was assumed. Source mechanisms were inverted for the moment tensor. The application of a more sophisticated medium model improved inversion quality only for some events. Introducing the source directivity, a standard approach for earthquakes with magnitudes larger than approximately 4, increased the number of successfully inverted events. Directivity was introduced using a Haskell source model; optionally unilateral and bilateral versions of the source were considered. Lower values of RMS for the Haskell source model were considered to justify the directivity approach. This formalism enables us to select the preferable fault from the two nodal planes within the fault plane solution. The rupture directions were observed to tend to the dip direction of the preferred fault. They were found to be preferably subparallel to slip directions for acoustic emissions with a significant DC component. The source time functions retrieved from the seismograms are in agreement with finite source theory.

中文翻译:

根据源方向性解释的声发射事件

在实验室声发射事件的源机制反演期间,观察到相对较高的失配值(表示为反演方程的 RMS)。我们的实验是在 Westerly Granite 上进行的。使用了一组由 2405 个声发射事件组成的处理数据,并考虑了半均匀速度模型。考虑了对传感器辐射模式和单个传感器常数的校正,并假设了非因果衰减模型。对于矩张量,源机制被反转。更复杂的介质模型的应用仅提高了某些事件的反演质量。引入震源方向性(震级大于 4 级地震的标准方法)增加了成功反演事件的数量。方向性是使用 Haskell 源模型引入的;可选地考虑了来源的单边和双边版本。Haskell 源模型的 RMS 值较低被认为可以证明方向性方法的合理性。这种形式主义使我们能够从断层解决方案中的两个节点平面中选择优选断层。观察到破裂方向倾向于优选断层的倾角方向。发现对于具有显着 DC 分量的声发射,它们优选地与滑移方向次平行。从地震图中提取的震源时间函数与有限震源理论一致。Haskell 源模型的 RMS 值较低被认为可以证明方向性方法的合理性。这种形式主义使我们能够从断层解决方案中的两个节点平面中选择优选断层。观察到破裂方向倾向于优选断层的倾角方向。发现对于具有显着 DC 分量的声发射,它们优选地与滑移方向次平行。从地震图中提取的震源时间函数与有限震源理论一致。Haskell 源模型的较低 RMS 值被认为是证明方向性方法的合理性。这种形式主义使我们能够从断层解决方案中的两个节点平面中选择优选断层。观察到破裂方向倾向于优选断层的倾角方向。发现对于具有显着 DC 分量的声发射,它们优选地与滑移方向次平行。从地震图中提取的震源时间函数与有限震源理论一致。发现对于具有显着 DC 分量的声发射,它们优选地与滑移方向次平行。从地震图中提取的震源时间函数与有限震源理论一致。发现对于具有显着 DC 分量的声发射,它们优选地与滑移方向次平行。从地震图中提取的震源时间函数与有限震源理论一致。
更新日期:2020-06-08
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