北天山中段地震精定位研究

STUDY ON PRECISE POSITIONING OF EARTHQUAKES IN MIDDLE SECTION OF NORTH TIANSHAN MOUNTAINS

为探究北天山中段主要发震构造,进一步明确重点监视区域。利用双差定位法对2010年6月至2021年12月期间在北天山中段发生的M_(S)≥1.5的1439个地震事件进行重定位。得到结果:①走时残差均值由-0.22 s变为0.0066 s,震源位置测定误差在东西向上平均为1.1 km,在南北向上平均为1.4 km,在垂直深度上平均为2.0 km。②地震主要分布在乌鲁木齐山前坳陷及南部区域,并未向准噶尔盆地延伸;局部地震震中向构造带趋近,呈现出一条走向近280°、一条近300°的地震活动带,分别与准噶尔南缘断裂带、亚马特断裂带走向基本一致。③由深度剖面显示,震源深度分散程度增加,0-50 km均有分布。以乌鲁木齐为界,东西两侧地震震源深度存在明显的差异,呈现出东深西浅的现象。通过对该区域精定位研究,初步探明准噶尔南缘断裂带、亚马特断裂带为该区域主要发震构造,盆山结合部地震较为活跃,因此准噶尔南缘断裂带及乌鲁木齐山前坳陷区将作为今后震情跟踪工作的重点监视区域。

In order to explore the main seismogenic structures in the middle section of the North Tianshan Mountains and further define the key monitoring areas,this paper uses the double-difference positioning method to relocate 1439 seismic events with M_(S)≥1.5 occurred in the middle section of the North Tianshan Mountains from June 2010 to December 2021.The results are as follows:①Mean value of traveltime residuals changes from-0.22 s to 0.0066 s,and the average error of source location determination is 1.1 km in east-west direction,1.4 km in north-south direction,and 2.0 km in vertical depth.②Earthquakes were mainly distributed in the Urumqi piedmont depression and the southern region,and did not extend to the Junggar basin;The local earthquake epicenter approaches to the tectonic zone,showing a seismic active zone with a strike of nearly 280°and a strike of nearly 300°,which are basically consistent with the southern margin fault zone of Junggar and the Yamat fault zone.③According to the depth profile,the dispersion degree of focal depth increases,and it is distributed from 0 to 50 km.Taking Urumqi as the boundary,there are obvious differences in the focal depths of earthquakes on the east and west sides,showing the phenomenon of deep in the east and shallow in the west.Through the precise positioning study of the region,it is proved that the southern margin fault zone of Junggar and the Yamat fault zone are the main seismologic structures in the region,and the earthquakes in the basin-mountain junction are relatively active.Therefore,the southern margin fault zone of Junggar and the Urumqi piedmont depression area will be the key monitoring areas for the earthquake tracking work.