2022年门源地震序列揭示的断层几何形状及滑动特性

Fault geometry and slip characteristics revealed by the 2022 Menyuan earthquake sequence

2022年门源地震序列的发生为周围断裂特性研究提供了新的资料.为研究门源地震序列所在的冷龙岭断裂和托莱山断裂形状,本研究首先搜集了2022年门源地震序列的地震观测资料,对地震事件进行双差精定位,获得了765个精定位地震事件,然后采用本研究改进的基于模糊聚类的断层面形状确定方法得到了冷龙岭断裂、托莱山断裂及北冷龙岭断裂的走向和倾角.为进一步研究这些断层的滑动性质,本研究搜集了发生在冷龙岭断裂和托莱山断裂及其邻区的中强地震震源机制,求解了该地区的走滑兼逆冲的构造应力场,区域应力场结果可以理解为青藏高原东北缘的东北向扩展所致.将求解得到的构造应力场投影到冷龙岭和托莱山断裂上,发现这两条断裂均表现为走滑兼逆冲的地质活动.另外2022年门源地震序列有少量事件发生在北冷龙岭断裂,为检验这些事件是否为2022年门源地震破裂所触发,求解了2022年门源地震在北冷龙岭断裂上的库伦破裂应力变化,发现2022年门源地震促进了北冷龙岭上地震的产生.这些研究对认识该地区的断裂活动特性和地震动力学有一定意义.

The occurrence of the 2022 Menyuan earthquake sequence provides new data for the study of the properties of the surrounding faults.In order to study the geometry of Lenglongling and Tuolaishan fault where the Menyuan earthquake sequence is located,the seismic observation data of 2022 Menyuan earthquake sequence is collected,and the precise location of 765 seismic events is accurately determined.Then,the strike and dip angle of the Lenglongling,Tuolaishan and North Lenglongling faults are estimated by using the improved fuzzy clustering method.In order to further study the slip properties of these faults,the focal mechanisms of moderate or strong earthquakes near the Lenglongling,Tuolaishan faults and their adjacent areas are collected,and the tectonic stress field in this area is determined,which shows a thrust and strike-slip stress pattern resulted from the extension of the north-eastern margin of the Tibet-plateau.Projecting the determined tectonic stress field on the Lenglongling and Tuolaishan faults,it is found that the geologic activity on the two faults shows strike-slip and thrust activity.In addition,a small number of events occurred in the North Lenglongling fault in the 2022 Menyuan earthquake sequence.In order to test whether these events were triggered by the 2022 Menyuan earthquake rupture,the Coulomb failure stress change on the North Lenglongling fault caused by the 2022 Menyuan earthquake was calculated,it is found that the Menyuan earthquake in 2022 promoted the earthquakes occurrence on the North Lenglongling fault.These studies are of significance for understanding the characteristics of fault activity and earthquake dynamics in study region.