The Detectability of Microseismic Events Using Surface Arrays

Recently there has been much interest in using data from surface arrays for passive seismic monitoring, where migration-based processing methods can be used to locate events in both space and time. Here we test the sensitivity of such methods to signal to noise ratio using signals embedded in different amounts of realistic noise. The data for this study consist of signals recorded across a temporary array of surface instruments in Wyoming, whilst a perforation shot was detonated in the subsurface. Applying a stacking procedure to the data with different signal to noise ratios demonstrates that surface arrays in conjunction with migration style processing methods can successfully image sources that are too weak to be observable in the raw data. The results show that the imaged shot position is relatively insensitive to the level of added noise. The primary effect of adding noise is that it defocuses the image of the shot location. We find that given our migration approach, the experiment geometry and recording conditions for the Wyoming dataset, signals embedded in noise with signal to noise ratios >0.1 can be successfully used to image and locate events.