Surface passive seismic monitoring by the local use of semblance

Summary Monitoring of passive seismic sources generated by mining activities and hydraulic fracturing has an important role in hazard analysis and in development of unconventional reservoirs. Surface arrays are vastly used in such monitoring scenarios with the advantage of wider spatial monitoring aperture, thus monitoring larger volumes over downhole arrays. However, signal-to-noise ratio of surface array records is naturally low. That makes application of coherency-based techniques an appropriate option for surface monitoring. Polarity variations corresponding to the source mechanism across the moveout curves/surfaces is a complicating task in the use of coherency-based monitoring methods to locate passive seismic events. To overcome this issue, we suggest a straight-forward approach that applies semblance, as a coherency analysis tool, on separate clusters of stations followed by averaging the results from all the clusters. To evaluate the performance of the suggested approach, we applied it on a semi-synthetic passive seismic data example generated from a reverse-oblique source and compared the result with the outcome from application of the classic coherency-based technique. It shows the ability of the suggested method to overcome polarity variations task, without conducting any polarity correction step.