Study on optimization of vertical location accuracy of seismic source based on joint monitoring of surface and underground micro-seismic monitoring

The vertical position of the seismic source is an important basic data for studying the mechanism of coal mine rock burst， which is of great significance for the monitoring and prevention of rock burst disaster.For the near-level coal seam working face，due to the small height difference between the microseismic stations， the partial differential matrix of the source parameters is nearly singular when the source location calculation is performed， and the iterative calculation cannot converge to an accurate solution.By using the optimization numerical simulation technology， the coal mine microseismic network is simulated under the conditions of reasonable height difference and no height difference of the station shows that the positioning error of the vertical position of the source is large when the stations in the network are in the same horizontal plane.In order to solve this problem，the ground microseismic monitoring stations are added on the basis of the underground microseismic monitoring to form a joint monitoring network， effectively optimizing the spatial structure of the microseismic monitoring network， especially the vertical direction of the stations.Monitoring effectiveness of common monitoring can reach to 90% for the event of 102； Monitoring effectiveness of common monitoring can reach to 100% for the event of 103 and more； By comparing the data of microseismic events caused by 10 groups of downhole top blasting， it is found that the positioning results of the underground microseis-mic monitoring system are basically located within the sealing range of 30 m above the coal seam， while locations of common monitoring network are within 30m-60m from blasting above the coal seam.Compared with the positioning results using the downhole monitoring stations alone， the positioning results of the combined microseismic monitoring system above and below the well are generally closer to the true source， indicating that the addition of ground monitoring stations effectively improves the vertical positioning of the source， effectively solves the problem of large vertical positioning error of near-level coal seam microseismic events.