通过理论地震图模拟，研究sPn震相特征，分析其影响因素。研究表明：sPn与Pn震相的初动极性关系在不同台站方位角呈现不同特点，基于sPn震相的深度定位方法更适合于中强地震。以2012年9月7日12时16分彝良Ms5.6地震为例，利用南北地震带南段密集流动地震台阵的观测数据，采用波形互相关方法拾取Pn波走时，应用滑动时窗相关法识别sPn震相，通过sPn与Pn震相之间的走时差测定其震源深度为9.6km。

With modeling theoretical seismograms, we studied the characteristics of sPn phase and analyzed the factors that may affect the phase. The result showed that the polarity of sPn with different azimuth angle may be different, and the depth location method based on the sPn phase is more suitable for M4.0-6.0 earthquakes. Taken the Yiliang Ms5.6 ecent on September 7 ,2012 as an example, we obtained its focal depth is 9.6 kmusing the seismic waveforms recorded by the seismic array deployed in the southern section of the North-South seismic belt. The focal depth is determined from the arrival-time differences between sPn and Pn phase. The Pn waves are picked by the waveform cross-correlation method, and the sPn phases are identified by using the sliding-window correlation method.