摘要
采用多层地壳模型下的主事件发震时刻与从事件的震相走时差对主事件位置参数偏导数最速下降得到从事件位置的主事件定位法,称为“对震源时空参数求梯度的主事件定位法”。采用均匀和速度成层的地壳模型对上述方法进行模拟数据检验,结果表明:(1)在均匀的台站分布条件下,从事件定位误差随着主事件和从事件之间距离的增大而增大。(2)在台站不均匀分布的条件下,在缺失台站方向上从事件定位误差变大;反之,在台站密度越大的方向上,从事件定位越准确。(3)主事件不准确的条件下从事件位置与主事件的位置相关。因此,从事件距主事件达到一定阈值后不推荐使用主事件定位法,并且采用主事件定位法一定要保证主事件位置的精度。将该定位方法用于西藏定日MS6.8地震余震序列,使残差由原来0.660 s降低至0.275 s,得到4210次地震的精确地震位置。定位结果显示地震大致可以分成南北两个丛集,并采用模糊聚类确定断层面方法得到:断层面A走向179.8°,倾角83.2°;断层面B走向161.6°,倾角47.4°。这些结果为该地震孕育结构研究和地震动力学分析提供了基础。
In this study,a master-event location method that determines the epicenter location of slave-event through steepest descent of partial derivatives of travel-time differences between master and slave events in multi-layered crustal model with respect to parameters of epicenter location of master-event.This approach is termed“master event location method based on gradient with respect to source spatiotemporal parameters.”Synthetic tests were conducted by using a homogeneous and layered crustal velocity model,which revealing that:(1)Under uniform station distribution,the location error of slave-event increases with the distance of epicenter location between the master-event and the slave-event.(2)With uneven station distribution,the location error of slave-event decreases in directions with lacking station coverage.Conversely,the higher the station density in a given direction,the more accurate the slave event location will be.(3)Slave-event locations exhibit dependency on the master-event position when the latter is inaccurately determined.Consequently,it is not recommended to use the master-event locating method when the distance between the slave-event and the master-event reaches a certain threshold.And the accuracy of the master event location must be ensured when using the method.By applying the master-event locating method to the aftershock sequence of the 2025 Dingri M_(S)6.8,Xizang earthquake,the travel time residuals reduced from 0.660 s to 0.275 s,yielding precise locations for 4210 events.The relocation results indicate that the earthquakes can be divided into northern and southern clusters.Using the method of fault plane determined by the fuzzy clustering,the following parameters were identified:Fault Plane A has a strike of 179.8°and a dip of 83.2°;Fault Plane B has a strike of 161.6°and a dip of 47.4°.These findings provide fundamental constraints for investigating the seismogenic structure and earthquake dynamics analysis of Dingri M_(S)6.8,Xizang earthquake.
作者
万永革
彭胥丰
WAN Yongge;PENG Xufeng(Earth Science and Engineering School,Institute of Disaster Prevention,Sanhe 065201,China;Hebei Key Laboratory of Earthquake Dynamics,Sanhe 065201,China)
出处
《防灾科技学院学报》
2025年第4期62-71,共10页
Journal of Institute of Disaster Prevention
基金
国家自然科学基金(42174074、42364005、41674055)。
关键词
地震重定位
主事件定位法
多层地壳模型
地震震相
走时
earthquake relocation
master-event location method
multi-layered crustal model
seismic phases
travel time
