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基于绝对走时计算的地面微地震监测地震发射层析成像(Seismic emission tomography,SET)定位算法的定位精度受地层速度模型的准确性影响很大,速度模型中的误差会使定位结果出现偏差.本文提出了一种基于相对走时计算的地面微地震监测SET定位算法,以克服绝对走时计算对速度模型精度的高度依赖.首先,通过分析走时误差推导了相对走时计算公式.然后,利用该公式对射孔初至进行校正,得到射孔点附近其他待监测网格点的走时.通过数值模拟和实际资料测试,结果表明在基于SET定位算法的前提下,本文提出的相对走时计算方法能得到比绝对走时计算方法更准确的定位结果.
Ground microseismic monitoring based on absolute traveltime calculation The localization accuracy of the SET (Seismic emission tomography) positioning algorithm is greatly affected by the accuracy of the formation velocity model, and errors in the velocity model may lead to the deviation of the positioning results. Aiming at solving the problem that the absolute travel time is highly dependent on the accuracy of the speed model.Firstly, the formula of relative travel time is deduced by analyzing the travel time error.Then, The initial time of the hole is corrected to obtain the travel time of other grid points to be monitored near the perforation point.According to the numerical simulation and actual data test, the results show that the relative travel time calculation method proposed in this paper can get more absolute Travel time calculation method more accurate positioning results.