台站分布对不同方法定位结果的影响程度——以芦山余震为例

Stations Distribution Influence on Locating Results Calculated by Different Methods——a Case Study of Lushan After-shocks

选取四川测震台网记录的芦山Ms7.0地震余震资料,在保证相同地震台站及相同震相到时的前提下,台站空隙角在25°~320°范围内任意变化,分别采用MSDP中常用的Hyposat、HYP2000、locSAT和单纯形等定位软件,在相同速度模型下进行多次定位,并对定位震中位移误差进行分析,结果表明:震中位移误差随着空隙角的增大而逐步变大,震中位移范围Hyposat为0.2~11.6 km、HYP2000为0.1~9.9 km、locSAT为0.4~11.4 km、单纯形为0.2~14.1 km;LocSAT的震中位移误差整体变化相对平稳,起伏不大,该方法适用于本研究中的所有定位地震;在台站空隙角大于240°时,单纯形的震中位移误差会出现随机突跳现象,该方法不适用于台站空隙角较大的地震定位。

We first collect the data of the MT. 0 Lushan After-shocks from Sichuan Seismic Network and then use different location software to test the influence on locating results in the condition of triangle between 25 to 320 de- gree formed by two seismic stations and the epicenter. The location software we use is HypoSat, Hypo 2000, LocSat and HypoInverse 2000. For the earthquakes occurred in the inner of seismic network, the location results calculated by HypoInverse 2000 and Hypo 2000 are better than that of HypoSat. For the earthquake occurred at the edge of seismic network, three software give out almost same results. 4 software packages use some velocity model. Our re- sults show that the location error increases with the gap angle gradually increasing. The error calculated by HypoSat is from 0. 2 to 11.6 km. The error calculated by Hypo 2000 is from 0. 1 to 9.9 km. The error calculated by LocSat is from 0. 4 to 11.4 kin. The error calculated by HypoInverse2000 is from 0. 2 to 14. 1 km. The overall changes of epicenter location calculated by LocSat are relatively smooth and undulating. All the earthquake location methods are suitable for this study.