钟世军,吴建平,司政亚,朱红彬,王薇. 2024. 基于程函面波成像的华北克拉通岩石圈三维高分辨率S波速度结构研究. 地震学报,46(4):1−22. doi: 10.11939/jass.20230052
引用本文: 钟世军,吴建平,司政亚,朱红彬,王薇. 2024. 基于程函面波成像的华北克拉通岩石圈三维高分辨率S波速度结构研究. 地震学报,46(4):1−22. doi: 10.11939/jass.20230052
Zhong S J,Wu J P,Si Z Y,Zhu H B,Wang W. 2024. High-resolution S-wave velocity structure of the lithosphere beneath North China Craton based on Eikonal surface wave tomography. Acta Seismologica Sinica46(4):1−22. doi: 10.11939/jass.20230052
Citation: Zhong S J,Wu J P,Si Z Y,Zhu H B,Wang W. 2024. High-resolution S-wave velocity structure of the lithosphere beneath North China Craton based on Eikonal surface wave tomography. Acta Seismologica Sinica46(4):1−22. doi: 10.11939/jass.20230052

基于程函面波成像的华北克拉通岩石圈三维高分辨率S波速度结构研究

High-resolution S-wave velocity structure of the lithosphere beneath North China Craton based on Eikonal surface wave tomography

  • 摘要: 利用“中国地震科学台阵探测”项目Ⅱ期和Ⅲ期的流动地震台站以及中国区域地震台网中的部分固定台站的观测资料,采用程函面波成像方法获得了华北克拉通及周边区域10—120 s周期的瑞雷面波相速度分布和高分辨率的三维S波速度结构,并基于该速度模型估算了岩石圈厚度分布。结果显示,华北克拉通内部岩石圈厚度除存在“西厚东薄”的一级分布特征外,还存在一些更小尺度的差异,包括鄂尔多斯地块内部岩石圈“南厚北薄”、鄂尔多斯地块周缘断陷带岩石圈显著的不均匀减薄以及燕山构造带与其南侧华北平原之间的显著差异等。山西断陷带北部与南部地区上地幔浅部(<100 km)存在不同程度的低速异常,它们被中部的高速异常区所分隔。在150 km以下深度从太行山南缘向北至山西断陷北缘存在一条NNE向展布的显著低速异常带,表明上地幔浅部南北部的低速异常在深部相连。结合已有的其它成像结果,我们推测这些低速异常起源于更深处(>200 km),并与由太平洋俯冲板块的滞留脱水导致上地幔热物质上涌和小尺度地幔对流等密切相关。燕山构造带与华北平原的岩石圈结构存在明显差异,前者遭受的岩石圈破坏改造程度明显弱于后者,张家口—渤海地震带位于这两种不同壳幔结构的过渡带,地震活动性较强,我们认为深部结构和热作用的显著差异,以及青藏高原远场挤压效应的共同作用是导致该区地震活动性较强的主要原因。

     

    Abstract: We have obtained high-resolution Rayleigh surface wave phase velocity at 10−120 s and three-dimensional S-wave velocity structure from Eikonal surface wave tomography in North China Craton and its surrounding region.Furthermore, we have estimated the lithosphere thickness based on this S-wave velocity model.The surface wave data in this study comes from the portable stations of ChinArray Phase Ⅱ and Ⅲ, and some permanent stations of China National Seismic Network (CSN).The rusults showed that there are some smaller scale variations of the lithosphere thickness in the North China Craton in addition to the first-order distribution characteristics of ‘thick in the west and thin in the east’. Which includes (1) within the Ordos block, the lithosphere is thinner in the north than that in the south, (2) within the peripheral rift zone around Ordos block, it is characterized by significantly heterogeneous thinned lithosphere, and (3) there is significant difference between Yanshan Orogenic Belt and North China plain on its south side.In Shanxi rift zone, both the northern and southern regions exhibit varying degrees of low velocity anomalies in the upper mantle (<100 km), which are separated by a high velocity anomaly zone in the central area.At depth of more than 150 km, a remarkable low-velocity anomaly belt oriented NNE is observed from the southern edge of Taihang Mountain to the northern edge of Shanxi rift zone, indicating that the shallow upper mantle low-velocity anomalies are connected in the deep.Combined with some other research findings, we speculated that these low-velocity anomalies may stem from a greater depth (>200 km), potentially linked with the stagnant dehydration of the subducted Pacific plate and consequent upwelling of thermal material in the upper mantle, as well as small-scale mantle convection.The lithospheric structures of the Yanshan Orogenic belt is significantly different from North China Plain, with former experienced much less destruction and reconstruction. Zhangjiakou-Bohai seismic zone is located at the transitional region between these two distinct crust-mantle structures, and characterized by intense seismic activity.We concluded that the combination of significant differences in deep structure and thermal action, as well as the far-field extrusion effect of the Qinghai-Tibet Plateau, mainly contributes to the intense seismic activity in this zone.

     

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