Influence of the Double-couple Source Model on the Sensitivity of Microseismic Monitoring Networks

Microseismic monitoring has significant interest of researchers as well as operators of the hydraulic stimulations or material extractions. It is necessary for the successful monitoring to design the monitoring network in order to be able to locate seismic events above certain threshold of magnitude with sufficient accuracy. The detection threshold becomes more complicated if one considers double-couple (shear) source mechanism therefore the average values of the radiation pattern of the source are widely used. In this study we are illustrating how the double-couple source radiation can be included in network design. We discuss influence of the three main classes of mechanisms: strike-slip source mechanisms, normal (reverse) faulting mechanisms and unknown orientation of the source mechanisms. The specific sensitivity distributions are computed by the empirical relationships for the surface network of 4 stations and for single borehole array. These simulations showed, that the radiation pattern of the seismic sources can have large influence on the sensitivity of the monitoring networks (especially limited networks like surface network of 4 stations or single borehole array). We showed also the influence of the unknown orientation of the source mechanisms sensitivities compared with the sensitivities computed by using average values of the radiation pattern.