Research on microseismic interferometric location method based on the instantaneous phase

The waveform stacking-based location methods have been widely used for the microseismic event location due to their automaticity and noise-resistance. The imaging resolution of these methods will be reduced when characteristic functions for original waveform transformation are used to overcome the effect of first-motion polarity changes. Although the imaging resolution is improved, the phase-weighted stack method does not consider the effect of complex source mechanisms on location when it is applied to microseismic imaging. In order to correct the waveform polarity, and to further improve the resolution and noise-resistance ability of the interferometric imaging method, this work proposes a cross-correlation phase-weighted (CCPW) imaging method which recombines the amplitude and instantaneous phase information of the original cross-correlation waveform. The performance of the cross-correlation phase-weighted (CCPW) imaging method, absolute value-based interferometric imaging (AII), and short-term average to long-term average ratio (STA/LTA)-based interferometric imaging (SLII) is investigated by numerical examples, in terms of noise-resistance, imaging resolution and so on. The numerical tests indicate that the new method can address the first-motion polarity changes, have strong anti-noise performance, and improve the imaging resolution. Finally, these three methods are applied to field mining-induced seismicity monitored by surface stations and the effectiveness of the new method is verified.