2021年滦州M_(S)4.3地震地磁场同震异常变化分布与断裂构造的关系

The relationship between the distribution of coseismic geomagnetic field anomaly and fault structure of the Luanzhou M_(S)4.3 earthquake in 2021

基于2021年滦州M_(S)4.3地震前后16 d内的流动地磁观测资料,经地磁场的日变通化改正、长期变化改正及差值计算后,获得了震中区域地磁场同震变化特征。结果表明,滦州地震地磁场同震变化总体较小,可能与震中区域地壳介质较为破碎、不易积累较大地壳应力有关。震中位于地磁场水平矢量方向变化的转向区及幅值变化的弱化区,并在震中附近分布有地磁总强度、地磁偏角、地磁倾角的“0”变线。地磁场同震异常变化分布与断裂构造关系密切,宁河—昌黎断裂和滦县—乐亭断裂基本控制着地磁场异常变化的分布,围绕两条断裂交会处,地磁场异常变化分布具有明显的差异性,可能与宁河—昌黎断裂和滦县—乐亭断裂的相互作用导致应力场变化的非均匀性有关。

Based on the mobile geomagnetic observation data within 16 days before and after the Luanzhou M_(S)4.3 earthquake,the variation characteristics of the coseismic geomagnetic field in the epicentral area are obtained after the diurnal variation correction,long-term variation correction and difference calculation of the geomagnetic field.The results show that the coseismic geomagnetic field variation of the Luanzhou earthquake is generally small,which may be related to the fact that the crustal medium in the epicentral area is relatively broken and it is not easy to accumulate large crustal stress.The epicenter is located in the turning area of geomagnetic horizontal vector direction change and the weakening area of amplitude change,and there are“0”variation lines of geomagnetic total intensity,geomagnetic declination and geomagnetic inclination near the epicenter.The distribution of coseismic geomagnetic field anomaly is closely related to the fault structure.The Ninghe-Changli fault and Luanxian-Leting fault basically control the distribution of geomagnetic field anomaly variation.Around the intersection of the two faults,the distribution of geomagnetic field variation has obvious differences,which may be related to the inhomogeneity of stress field variation caused by the interaction of Ninghe-Changli fault and Luanxian-Leting fault.