Statistically Optimal Technique of Simultaneous Event Location and Focal Mechanism Determination of Weak Microseismicity Using Surface Arrays

Summary In this paper we show that complex radiation patterns of microseismic events appear to cause false detections and degrade event location accuracy of conventional surface array microseismic processing techniques. A computational procedure for microseismic monitoring with 1 and 3-C surface arrays is proposed. The procedure is based on maximum likelihood statistic approach considering noise affecting array sensors as correlated in time and between sensor components. Along with enhancement of reliability and accuracy of the source location the procedure allows for simultaneously estimating the parameters of the source mechanism. All available information about medium structure and source mechanism can be accounted for in this procedure. Its efficiency was tested using simulated mixtures of synthetic array seismograms with real array noise recordings. Significant improvements of location accuracy and detection capability threshold were established when compared with the conventional Seismic Emission Tomography (SET) processing.