Conclusions

Microseismic source localization can be improved by migration-type diffraction imaging methods that stack passive seismic events along the moveout curves.

Compared to depth migration, diffraction-type time-domain migration is less sensitive to the subsurface velocity model. Path-integral migration can focus microseismic events in time-domain efficiently using only crude velocity limits. It can also serve as a tool for providing velocity information.

By spraying seismic data into a time-reverse shift hypercube, migration is performed on each slice of the shifted data and results in a time-shifted migration image that resembles the propagation of microseismic wavefield. By stacking the envelope along time-reverse shift axis, energies are focused at sources locations in the time-domain image. Our synthetic examples show that the proposed method can be stable in the presence of random noise and velocity heterogenities.