Localization of Seismic Events in 3D Media by Diffraction Stacking

The localization of seismic events is of great importance in exploration geophysics for monitoring of for instance hydraulic fracturing. It can be successfully implemented by diffraction stacking, where the source location is obtained from the maximum of the image function. Since the maximum of the image function is distinct, even in the presence of noise very weak events can be detected. Previous research showed that the method works reliably for homogeneous 2D media. In this paper we demonstrate the extension to 3D and present numerical examples in both homogeneous and heterogeneous media. Strongly heterogeneous media are intensely affected by triplications. We show that the localization of events in such media is nevertheless possible if the most energetic arrivals are taken into account. Moreover, by using geometrical spreading as weighting factors for the input data, separation of propagation and source effects is achieved. We have studied the source effects of radiation patterns. Finally, the method was tested on field data from Southern California. Both numerical and field data application confirm the potential of the method. Conventional source location methods by event picking locate the event with a maximum spatial deviation of 1 km when compared to the location method presented here.