Picking versus stacking in a modern microearthquake location: Comparison of results from a surface passive seismic monitoring array in Oklahoma

摘要

We present location results for a group of similar to 200 microearthquakes that occurred in 2012 in a region of Oklahoma hosting ongoing exploration activities. Using a local passive surface seismic monitoring network of 15 broadband stations, we applied two modern location techniques that use fundamentally different approaches. The first is a pick-based double-difference relocation method with waveform crosscorrelation. Multiple-event location techniques such as these are generally regarded as the best approach for obtaining high-precision locations from pick data. The second approach is an automated waveform migration stacking method. These types of methods are becoming increasingly common due to increasing network station density and computer power. The results from the two methods show excellent agreement and provide similar results for the interpreter. Both methods reveal spatial and temporal patterns in the locations that are not visible in results obtained using a more traditional pick-based approach. We performed two statistical uncertainty tests to assess the effects of data quality and quantity on the two methods. We show that the uncertainties for both methods are comparable, but that the stack-based locations are less sensitive to station geometry, likely due to the different treatment of outliers and the beneficial inclusion of noisier data. Finally, we discuss the favorable conditions in which to apply each method and argue that for small aperture surface arrays where accurate velocity information exists, such as in this study, the stack-based method is preferable due to the higher degree of automation. Under these conditions, stack-based methods better allow for rapid and precise determination of microearthquake locations, facilitating improved interpretations of seismogenic processes.