Locating the microseismic events is important in the safety assessment of mines and the reservoir impoundment and in the quality control of the hydraulic fracturing in the exploitation of gas and oil. However, due to the close arrivals of the microseismic clusters, it is a great challenge to accurately locate the microseismic clusters using the methods based on arrival times. Based on the reverse-time migration method, we proposed an approach using the joint of the reversed P wave field and S wave field to locate the microseismics. In this approach, we use the absolute records as the source functions in the reverse-time process and calculate the reversed wave fields (both P and S waves). Then, we pick out the origin times and the source locations of the microseismic clusters on the imaging condition of the focusing-to-scattering transformation of the wave front. We used synthetic data to test this approach, and the results indicate that this approach can successfully retrieve all the sources of the clusters.%微地震定位是油气资源开采中评估水力压裂质量和评估矿山地震和水库地震安全的重要手段.但是,采用地震震相到时定位的方法很难对具有相近到时的微地震事件群精确定位地震.本文尝试用P波和S波结合的逆时偏移方法对具有相近到时的微地震定位.先用绝对振幅记录做逆时偏移,获得P波和S波以及P波与S波结合的综合波场,再采用波前在震源位置成像前后的汇聚到散射的转换过程作为成像条件,提取震源位置和发震时刻.用数值模拟生成具有相近到时的微地震群,然后用该方法定位微地震.结果表明该方法可以有效提取各个震源位置和发震时刻.
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