山西襄垣-潞城M_(L)2.8有感震动事件类型判别

Identification of the Type of M_(L)2.8 Felt Seismic Event in Xiangyuan-Lucheng

以2019年12月15日山西长治市襄垣-潞城交界发生的ML2.8有感地震事件为例,从构造环境、频谱特征、震源参数、破裂机制、同期地震活动和现场调查等方面,对襄垣-潞城地震的震源特征进行分析。结果显示:襄垣-潞城地震具有较同区域地震相对低的频率分布、较低应力降和较大破裂尺度等特征,震源深度位于高低速转换层,且与之后区域同期密集发生的4次M_(L)≥3.0地震活动具有大体一致的主压应力轴方向,也与震源区赋存介质显示的所受NNE高主压应力作用方向接近。故研究认为襄垣-潞城地震是区域应力增强作用叠加在局部原有NNE向高主压应力的作用下,在矿区诱发的一次浅源地震事件,可能与矿区煤层气开采水压致裂注水,对震源区断层截面起到润滑作用而降低摩擦系数,区域较小的应力变化引起先存断裂活化有关。

Due to the complex record form and difficulty in type recognition of seismic events in the Changzhi area of Shanxi Province,this paper takes the M_(L) 2.8 earthquake that occurred at the junction of Xiangyuan and Lucheng in Changzhi,Shanxi on December 15,2019 as an example to analyze the source characteristics of the Xiangyuan-Lucheng earthquake from the aspects of structural environment,spectrum characteristics,source parameters,rupture mechanism,simultaneous seismic activity and on-site investigation.The results show that the Xiangyuan-Lucheng earthquake has the characteristics of relatively low frequency distribution,low stress drop,and large rupture scale compared with earthquakes in the same region,and the source depth is at the depth of the high-low velocity conversion layer.It has a generally consistent main stress axis direction with four M_(L)≥3.0 seismic activities that occurred intensively in the same region later,and it is also close to the direction of the high principal stress in the NNE direction shown by the existing media in the source area.Therefore,this study believes that the Xiangyuan-Lucheng earthquake was an earthquake induced by the regional stress enhancement superimposed on the local existing NNE high principal stress,which was induced in the mining area.This may be related to the fracturing of water injection in the mining area,which lubricates the fault section in the source area and reduces the friction coefficient,and the small stress change in the region activates the pre-existing fault.