Influence of a velocity model and source frequency on microseismic waveforms: some implications for microseismic locations
Influence of a velocity model and source frequency on microseismic waveforms: some implications for microseismic locations
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DOI：
10.1111/j.1365-2478.2012.01120.x
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发表时间：
2013-06
影响因子：
2.6
通讯作者：
P. Usher;D. Angus;J. Verdon
中科院分区：
文献类型：
--
作者：
P. Usher;D. Angus;J. Verdon
在本文中，我们研究了速度模型和微震震源频率对微震波形和事件位置的影响。在棉花谷压裂实验的基础上，通过改变速度模型的垂向非均质性和微震震源频率，产生了有限差分波形合成。我们发现，合理的速度模型之间的差异导致P波的到达时间约为0.0035秒，而S波的到达时间约为0.0085秒。根据P波和S波的平均速度，P波和S波走时之差相当于位置差约20m。随着模型非均质性的增加和震源频率的增加，波形尾波显著增加。信号噪声以及其他误差来源(例如，检波器位置的不确定性)的存在可能会导致位置误差估计的不确定性进一步增加。因此，我们注意到由不正确的速度模型引起的定位误差不能被忽略。
In this paper, we examine the influence of a velocity model and microseismic source frequency on microseismic waveforms and event locations. Finite‐difference waveform synthetics are generated based on the Cotton Valley hydraulic fracture experiment, where we vary the vertical heterogeneity of the velocity models as well as the microseismic source frequencies. We find that differences between plausible velocity models lead to changes in arrival times of approximately 0.0035 seconds for P‐waves and 0.0085 seconds for S‐waves. Based on the average P‐ and S‐wave velocities, the difference in the P‐ and S‐wave traveltimes is equivalent to approximately 20 m in location difference. Significant increases in the waveform coda develop with increasing model heterogeneity and increasing source frequency. The presence of signal noise as well as other sources of error (e.g., uncertainty in geophone location) will likely lead to further increase in uncertainty in location error estimates. Thus we note that location error due to incorrect velocity models cannot be ignored.