jgg     2013 33 (增1):  45-48    ISSN: 0412-1961  CN: 21-1139/TG ANALYSIS ON SEISMIC SOURCE DEPTH DETERMINATION  USING TRAVEL TIME DIFFERENCE OF sPn AND Pn PHASE Earthquake Administration of Ningxia Hui Autonomous Region, Yinchuan 750001 Received: 2013-10-23  Revised: null  Online: 2013-09-25 Supporting info