An Approach to Analyse Microseismic Event Similarity

We introduce two parameters to analyse the similarity of close seismic events. The first is an extension of the normalised cross correlation coefficient (composite correlation measure, CM), and the second parameter depends on differential arrival times (composite differential arrival time measure, TM). TM quantifies the separation of pairs of seismic events. The relationship between TM and interevent distance Delta-r is derived, and theoretical TM-Delta-r-distributions are calculated for different source-receiver geometries. We find that a combined analysis of the three parameters CM, TM and Delta-r is practical for identification of time measurement errors and mislocations. The envelope of the CM-TM plot delineates event pairs with the same source mechanism (multiplets). We define an area around this envelope in order to account for statistical uncertainties. Therefore we develope two different approaches to obtain a proper measure of this area.