黄翔,丁志峰,宁杰远,徐小明. 2022. 基于背景噪声和地震面波联合反演华北克拉通中部岩石圈结构. 地震学报,44(4):539−554. doi: 10.11939/jass.20210042
引用本文: 黄翔,丁志峰,宁杰远,徐小明. 2022. 基于背景噪声和地震面波联合反演华北克拉通中部岩石圈结构. 地震学报,44(4):539−554. doi: 10.11939/jass.20210042
Huang X,Ding Z F,Ning J Y,Xu X M. 2022. Joint inversion of the lithospheric structure of the central North China Craton from ambient noise and seismic surface wave. Acta Seismologica Sinica44(4):539−554. doi: 10.11939/jass.20210042
Citation: Huang X,Ding Z F,Ning J Y,Xu X M. 2022. Joint inversion of the lithospheric structure of the central North China Craton from ambient noise and seismic surface wave. Acta Seismologica Sinica44(4):539−554. doi: 10.11939/jass.20210042

基于背景噪声和地震面波联合反演华北克拉通中部岩石圈结构

Joint inversion of the lithospheric structure of the central North China Craton from ambient noise and seismic surface wave

  • 摘要: 基于ChinArray三期项目布设于华北克拉通中部的流动台阵观测数据,利用背景噪声互相关和地震面波层析成像获取了研究区内6—140 s周期的瑞雷面波频散,使用蒙特卡罗非线性反演方法获得了华北克拉通中部岩石圈的高分辨率三维S波速度结构。结果显示华北克拉通不同地块的岩石圈速度结构存在显著的横向差异:其中鄂尔多斯盆地腹地整体表现为高速特征,延伸至200 km以下,但其东南缘存在小范围的低速异常;东部的华北盆地整体表现为低速特征,具有较薄的地壳和岩石圈厚度;中部造山带南北两端以及南北重力梯度线下方存在相连接的低速区域,在深处延伸至华北盆地下方;在下地壳和上地幔顶部,大同火山群区域的低速体逐渐向西偏移至鄂尔多斯盆地东北角下方;而在上地幔中,该区域的低速异常随深度增加而逐渐减弱,低速体延伸至东南方向的华北盆地下方。基于本研究获得的S波速度模型,我们认为:鄂尔多斯盆地腹地保持了克拉通特性,但其东南缘存在局部的岩石圈改造作用;华北盆地发生了强烈的岩石圈破坏减薄和地壳伸展变形;中部造山带南北端以及南北重力梯度线下方的岩石圈发生了局部的改造减薄,其机制可能都来源于华北盆地下方地幔热物质的上涌;大同火山群下方上涌的热物质从鄂尔多斯盆地东北角下方侵入下地壳,在地壳内上升过程中受到上地壳的阻挡,向东流动至大同火山群下方,形成了大同火山群的岩浆活动,其深部来源可能与西向俯冲的太平洋停滞板块有关。

     

    Abstract: Based on the observation data of the ChinArray Phase Ⅲ deployed in the central North China Craton, the Rayleigh surface wave dispersion with period range of 6 s to 140 s in the studied area is obtained using cross-correlation of ambient noise and seismic surface wave tomography. The high-resolution 3-D S-wave velocity structure of the lithosphere in the central North China Craton is further obtained with the Monte Carlo nonlinear inversion method. The results exhibit significant lateral differences in the lithospheric structure of different blocks of the North China Craton. The central part of the Ordos basin is characterized by high velocity overall, extending below 200 km, but there is a small range of low-velocity anomalies on the southeast margin. The North China basin in the east is characterized by low-velocity with thin crust and lithospheric thickness. Connected low-velocity zones at the northern and southern ends of the central orogenic belt and below the north-south gravity gradient line are observed, which extends below the North China basin. In the lower crust and uppermost mantle, the low-velocity zone in the Datong volcanic group area gradually shifts westward to the northeast corner of the Ordos basin. While in the upper mantle, the low-velocity anomalies in this area gradually fade off as the depth increased. And the low-velocity zone extended below the North China basin in the southeast. Based on the S-wave velocity model obtained in this study, we believe that the heart of the Ordos basin maintains the cratonic characteristics overall, but there is a local lithospheric modification at the southeast margin; the North China basin has experienced strong lithospheric destruction and thinning and crustal extensional deformation; the lithosphere at the northern and southern ends of the central orogenic belt and the north-south gravity gradient line has undergone partial modification and thinning. The mechanism may be the same and due to the upwelling of hot material in the mantle below the North China basin; the upwelling hot material below the Datong volcanic group intrudes into the lower crust below the northeast corner of the Ordos basin. Then it is blocked by the upper crust when rising in the crust and flows eastward to the bottom of the Datong volcanic group, forming the magmatic activity of the Datong volcanic group. The deep source may be related to the stagnant Pacific slab.

     

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