用sPn震相测定近震震源深度

用近震深度震相ｓＰｎ与Ｐｎ波的到时差测定近震深度，方法以求简捷准确。为此，对我国部分地区台网记录的ｓＰｎ震相进行了初步分析研究，通过研制的计算ｓＰｎ走时程序运算，给出华北、山西、华东、西北及四川地区的ｓＰｎ－Ｐｎ走时差对应震源深（ｈ）表和ｓＰｎ－Ｐｎ求震源深度列线图。经过震例检验，该表比较适合本地区的走时特性。为应用ｓＰｎ震相测准我国部分地区震源深度，提供了有利工具。

Determination of focal depth with the sPn phase

This paper discusses the determination of focal depth of near earthquakes by means ofthe arrival time difference between the sPn and Pn phases.This method is simple,quickand accurate. A preliminary analysis of the sPn phases recorded at part of local seismicnetworks in China has been made. With our program for the calculation of sPn traveltime, the table of travel-time difference of sPn-Pn corresponding to focal depth (h) hasbeen calculated in North China, Shanxi,East China, Northwest China and Sichuan regionsand a set of graphs for finding focal depth (h) from the travel-time difference of sPn-Pnhas been plotted. Verification with earthquake cases shows that this table suits the characteristics of travel time in these regions.The paper provides a useful tool for the accuratedetermination of focal depth of near earthquakes in part of China by means of the sPnphase.