Hybrid focal mechanism determination: constraining focal mechanisms of injection induced seismicity using in situ stress data
Hybrid focal mechanism determination: constraining focal mechanisms of injection induced seismicity using in situ stress data
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混合震源机制确定：使用现场应力数据约束注入诱发地震活动的震源机制
DOI：
10.1093/gji/ggy333
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发表时间：
2018
影响因子：
2.8
通讯作者：
Haring MO
中科院分区：
文献类型：
--
作者：
Mukuhira Y;Fuse K;Naoi M;Fehler MC;Moriya H;Ito T;Asanuma H;Haring MO
确定注采诱发微震的震源机制不仅为认识注采诱发地震的特征提供了有益的信息，而且也为描述储层中的裂缝系统提供了有益的信息。然而，由于有限的台站覆盖范围，仅用初动信息往往不能很好地确定微震的震源机制。我们提出了一种新的方法，以更好地约束流体诱发地震活动的第一运动震源机制，通过引入situstress信息估计从钻孔分析和井口压力。由于注水诱发的地震活动主要是由孔隙压力的增加引起的，因此我们可以利用原地应力大小/方向信息和注水井口压力来限制震源机制的范围。然后，从可用的第一运动数据估计的可能的震源机制的范围被约束的范围叠加的震源机制，可以从原位应力条件下滑动。使用合并的信息集对病灶机制的约束比从任何一个单独的数据集获得的约束更好。我们将我们的方法应用于在瑞士巴塞尔的水力刺激过程中记录的微震数据，其中的应力状态是从钻孔测量。我们的方法成功地约束的范围内的焦点机制，虽然约束的程度是依赖于可能的焦点机制的分布是一致的第一运动和分布是一致的应力条件。我们比较了我们的方法使用的数据，仅从附近的站与良好的约束的震源机制确定的第一个议案，记录了超过50个地面站的震源机制的范围。在最好的情况下，80%与第一次运动数据一致的震源机制被删除，因为它们与应力数据不一致。即使考虑到用于约束的应力信息的不确定性，震源机制的约束范围也包括具有0.86的显著高概率的真实震源机制。这证明了我们的方法的能力，以限制范围内的震源机制的情况下，有限的台站覆盖范围，以及其他地球物理数据引入地震分析的好处。
Determining the focal mechanisms of injection induced microseismicity provides beneficial information not only for understanding the features of induced seismicity but also for characterizing the fracture system in the reservoir. However, focal mechanisms of microseismicity are often not well determined with first motion information alone due to limited station coverage. We propose a new method to better constrain first motion focal mechanisms of fluid-induced seismicity by introducingin situstress information estimated from borehole analysis and wellhead pressure. Since injection induced seismicity is dominantly caused by increases of pore pressure, we can usein situstress magnitude/orientation information and the injection wellhead pressure to constrain the range of focal mechanisms. Then, the range of possible focal mechanisms estimated from available first motion data is constrained by superposing the range of focal mechanisms that can slip from thein situstress condition. The use of the combined sets of information places a better constraint on focal mechanisms than can be obtained from either of the individual data sets. We apply our method to the microseismic data recorded during the hydraulic stimulation in Basel, Switzerland where the stress state is known from borehole measurements. Our method successfully constrains the range of focal mechanisms, though the degree of constraint is dependent on the distribution of possible focal mechanisms that are consistent with the first motions and the distribution that are consistent with the stress condition. We compared the range of focal mechanisms constrained by our method using data from only nearby stations with well-constrained focal mechanisms determined from first motions that are recorded by more than 50 surface stations. In the best case, 80 per cent of the focal mechanisms that are consistent with the first motion data were removed because they were inconsistent with the stress data. The constrained range of focal mechanisms includes the true focal mechanisms with significantly high probability of 0.86 even considering the uncertainty in stress information that is used for constraint. This demonstrates the ability of our method to constrain the range of focal mechanisms in situations with limited station coverage, and the benefits of introducing other geophysical data into seismological analyses.
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DOI：
--
发表时间：
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期刊：
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影响因子：
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