2022年青海门源M_(W)6.9地震同震形变及断层滑动分布反演

Coseismic deformation and slip distribution of the M_(W)6.9 Menyuan,Qinghai earthquake revealed by Sentinel-1A SAR imagery

2022年1月8日,青海海北州门源县发生M_(W)6.9地震,震中位于青藏高原东北缘祁连地震带上冷龙岭断裂和托莱山断裂的交汇处.门源地震活动强烈,造成地表破裂明显,因此研究门源地震的发震机理,对评估周边区域及主要断裂的地震危险性具有重要意义.本文基于D-InSAR技术,利用升降轨Sentinel-1A SAR数据,获取门源地震的同震形变场.结果显示,同震形变主要集中在冷龙岭断裂和托莱山断裂的交汇处,形变长轴整体呈NWW-SEE,同震引发的升轨隆升形变量0.40 m,沉降量0.65 m,降轨隆升形变量0.80 m,沉降量0.70 m,升降轨视线向(LOS)形变呈现符号相反大小相近的特征,断裂运动以左旋走滑为主.以升降轨同震形变信息为约束条件,基于弹性半空间位错理论,采用两步法进行反演,获取门源地震断层的几何参数.结合该区域的地质构造得到断层面上的精细滑动分布,结果表明,断层破裂延伸至地表,破裂迹线长度达22 km.断层滑动主要集中在地下2~12 km,最大滑动量为4.2 m,位于地下7 km处.断层走向约为109°,倾角约为82°,释放的地震矩为2.67×10^(19)N·m,矩震级M_(W)6.9,反映出门源地震是一次高倾角浅源地震.最后,计算了同震位错对周边区域及主要断裂库仑应力加载的影响,结合余震分布特征,结果显示,冷龙岭断裂北侧及肃南—祁连断裂南侧库仑应力显著增加,最高达0.5 MPa.表明该区域的地震危险性相对较高,应持续关注.

On January 8,2022,an earthquake of M_(W)6.9 occurred in Menyuan County,Haibei Prefecture,Qinghai Province,China.The epicenter was located at the intersection of the Lenglongling fault and the Tuolaishan fault,which is the Qilian seismic zone,northeastern Qinghai-Tibet Plateau.Owing to the strong seismic activity and the obvious surface rupture in Menyuan.Thus,it is particularly important to study the seismogenic mechanism of Menyuan earthquake and to evaluate the subsequent seismic hazards of surrounding areas and major faults.In this paper,We generate the coseismic deformation fields of the M_(W)6.9 Menyuan,Qinghai earthquake with D-InSAR technology utilized the ascending and descending SAR imagery(IW model)produced by Sentinel-1 A satellites of EAS.Our results indicate that coseismic deformation of this earthquake distributed at the intersection of Lenglongling fault and Tolaishan fault,and represented a NWW-SEE shape.The uplift variable were 0.40 m and 0.80 m,and subsidence variable were 0.65 m and 0.70 m of the ascending and descending interferograms,respectively.The line of sight of deformation of the ascending and descending show that characteristic of the opposite in sign and similar in size.And the quality was sinistral strike-slip movement.Therefore,infer the Lenglongling fault was the main seismogenic fault of the Menyuan earthquake.Based on the elastic half-space dislocation theory,the fault geometric parameters of Menyuan earthquake were obtained with the ascending and descending InSAR deformation field,and the slip distribution along the fault was obtained by combining with the geological structure of this area.The inversion results of fault model indicate the fault rupture extended to the surface with a length of 22 km.And an obvious slip concentrated in 2~12 km in the depth and which was dominated by a sinistral strike-slip movement.The maximum slip was about 4.2 m in the depth of 7 km,the strike was about 109 o,and the dip was about 82 o.The total released moment was 2.67×10^(19)N·m,which is equivalent to M_(W)6.9.These data show that Menyuan earthquake is a high dip angle shallow earthquake event.Finally,we calculated the state of the coulomb stress on the surrounding region and major faults.Based on the optimal fault model,and combined with the spatial distribution characteristics of aftershocks,the results reveal that the coulomb stress on the north side of Lenglongling fault and the south side of Sunan-Qilian fault increased dramatically,with a maximum of 0.5 MPa.Hence,the seismic risk in these areas was relatively high and should be paid much attention.