Abstract: The rupture of underground rock caused by hydraulic fracturing usually occurs within a horizontal range of approximately 200 meters around the fracturing well.When seismic interferometry is used to recover reflected waves recorded by microseismic sensors, the reflected wave recovered on the virtual source side will have a cross-correlation function with a positive time lag, while the one recovered on the opposite side will have a negative time lag.Upon generating the seismic trace of the virtual source, if the cross-correlation function with positive time lag is taken, the information about the reflected wave with negative time lag will be lost.To address this limitation, this paper proposes a "summation method" for combining the cross-correlation functions with positive and negative time lags, and a "relative position method" for relating the position of the virtual source to those of the receiving point and the fracturing well.Using the proposed method, the information carried by the initially discarded reflected wave can be exploited, thus doubling the number of folds and improving the quality of the migration imaging remarkably.A numerical model together with microseismic surface monitoring data collected in Sichuan, China, were used to test the method.The results showed that the quality of the migration imaging of the virtual source was significantly improved, and was consistent with the time-migration profile of 3D surface seismic data at the same location.Moreover, the imaging events related to shallow reflected waves were more continuous, thereby confirming the effectiveness of the proposed method.