广东地震台网近震定位精度的经验性GT准则

Empirical Ground Truth Criteria for Location Accuracy of Near Earthquake on Guangdong Seismic Network

利用广东地震台网的固定台和流动台记录的2次人工爆破事件,通过随机模拟台网几何形态,获得了该台网近震定位精度的经验性GT(Ground Truth)准则。结果表明:地震定位精度与台网几何形态密切相关;当台网满足以下条件时近震震中定位精度优于2km,震源深度精度优于3km,具有95%的置信度:(1)震中距小于150km的台站数≥7;(2)一级方位角空区<180°;(3)震中距小于10km的台站数≥1。在评估震源深度精度时,发现对于壳内地震,可靠的近台数据能够提高震源深度的精度,而定位时震中距较大的台站数量的增加对震源深度的精度影响很小。最后,应用该GT准则对广东地震台网产出的地震观测报告进行了评估,获得了1160个GT2参考事件。

In this paper, we made use of two explosions recorded by permanent stations and temporal stations of Guangdong seismic network to develop empirical ground truth criteria for location accuracy of local earthquake on Guangdong seismic network. Using random simulation of network geometry, we found that location accuracy closely relates to network geometry, and epicenter is accurate to within 2 km and focal depth is accurate to within 3 km with a 95% confidence level when the network meets the following conditions： （1）there are 7 or more stations, all within 150 kin. （2）the primary azimuth gap less than 180~. （3）at least one station within 10 krn. In assessing the accuracy of the focal depth, we found that the reliable data of the nearest stations could improve focal depth accuracy of shallow earthquake, and it was hardly to improve focal depth accuracy by increase the number of stations with large epicentral distance. At last, the empirical GT criteria developed in this study, when applied to seismic report of Guangdong seismic network, yielded ! 160 GT2 events.