影响山西台网地震定位因素的定量分析

Quantitative Analysis of Factors Affecting SeismicLocation of Shanxi Network

基于山西地震台网现有的台站布局,利用数值模拟方法定量分析地壳速度模型、台网布局及震相拾取精度等因素对震源位置测定的影响,结果显示,3种因素对准确测定震源位置的影响不同。地壳速度模型中上地壳速度对震中位置的影响最大,而震中位置对莫霍面速度变化的反映更为灵敏。单独改变地壳速度模型引起的震中位置偏差通常不超过5 km,震源深度对地壳速度模型的变化十分敏感,尤其是莫霍面深度,最大偏差可能超过20 km。在不考虑其他因素的条件下,P波拾取精度在4 s以内测定的震中位置和震源深度最大偏差不超过2 km和5 km。当地壳速度模型适宜且震相拾取精度较高时,最大空隙角在0°~180°的台站布局对震源位置的约束较好,震中偏差基本小于1 km,震源深度偏差略大(约为2 km)。

Using numerical simulation based on the existing station layout of Shanxi Network,we quantitatively analyze the effects of crustal velocity model,network layout and seismic phase picking accuracy on seismic source location.The results show that the three factors have different effects on the accurate location of seismic source.In the crustal velocity model,the upper crust velocity has the greatest influence on the epicenter location,and the epicenter location is more sensitive to the change of Moho velocity.The deviation of epicentral position caused by a single change of crustal velocity model is usually less than 5 km,the focal depth is very sensitive to the change of crustal velocity model,especially the Moho depth,and the maximum deviation may exceed 20 km.Without considering other factors,the maximum deviation between the epicenter position and the focal depth measured within 4 s with P-wave picking accuracy is not more than 2 km and 5 km.When the crustal velocity model is suitable and the seismic phase picking accuracy is high,the station layout with the maximum void Angle of 0°-180°has a better constraint on the focal location,the epicenter deviation is basically less than 1 km,and the focal depth deviation is slightly larger,about 2 km.