S波影区地震精确定位的研究

The study on the precise location of the seismic event in the shadow area of S wave

长期的地震观测发现,北京地震台记录到的S波影区地震存在定位误差大的现象。由于来自震中距9°～36°的地震经过了低速层,造成了S波不发育。所以S波影区地震多用LG波来确定震中距。造成影区地震定位偏差大的现象有两个原因:①长期以来多是用短周期记录来区分LG1和LG2,定位偏差较大;②有的影区地震,S波也少许发育,但用S波来定位也存在定位偏差大的现象。为此搜集了北京地震台记录到的影区地震,通过NCDSN仿真成SK记录,通过理论震中距的比较,找到了准确定位影区地震的LG2识别位置。

After long-term observation of earthquake,we found that the location error of seismic event in the shadow area of S wave is large.For pass through the low velocity zone,the S wave of earthquakes with epicentral distance of 9°~36° are weak,so the LG wave are used to determine the epicentral distance of the earthquake in shadow area of S wave.There are two reasons for the location deviation of shadow earthquake.One is that we usually distinguish the LG1 and LG2 phase with short period record for a long time,while the LG phase is not right identified.The other is that although some earthquakes in shadow area develop S wave in some extent,the location with S wave is also of large deviation.We gathered the seismic records of the region of the shadow and imitate this to a record of KIRNOS using NCDSN.By comparing with the theoretical epicentral distance,we find out exact discriminating position of LG2-wave which can be used to locate epicentral distance well.