We studied the depth phase sSmS and its reference phase SmS dominated by post-critical reflection from Moho using a series of synthetics and analyzed the factors that may affect the phase. The results showed SmS and sSmS were easy to observe in high frequency band （1Hz） , while difficult to identify on long-period seismograms. The complex crustal structure may also make it difficult to identify sSmS phases of events with shallow focal depth. Taken the Tengchong Ms5.2 event on June 20, 2011 as an example, we obtained its focal depth was 6km using depth phase sSmS, which was consistent with the result from the regional waveform modeling, sSmS can be used to determine focal depth with high precision.[著者文摘]