杨歧焱, 李大虎, 吴锋波, 梁明剑. 2019: 利用远震P波层析成像研究巴颜喀拉地块东缘及邻区的深部结构. 地震学报, 41(6): 695-708. DOI: 10.11939/jass.20190080
引用本文: 杨歧焱, 李大虎, 吴锋波, 梁明剑. 2019: 利用远震P波层析成像研究巴颜喀拉地块东缘及邻区的深部结构. 地震学报, 41(6): 695-708. DOI: 10.11939/jass.20190080
Yang Qiyan, Li Dahu, Wu Fengbo, Liang Mingjian. 2019: Deep structure of eastern margin of Bayan Har block and its adjacent areas by using teleseismic P-wave tomography. Acta Seismologica Sinica, 41(6): 695-708. DOI: 10.11939/jass.20190080
Citation: Yang Qiyan, Li Dahu, Wu Fengbo, Liang Mingjian. 2019: Deep structure of eastern margin of Bayan Har block and its adjacent areas by using teleseismic P-wave tomography. Acta Seismologica Sinica, 41(6): 695-708. DOI: 10.11939/jass.20190080

利用远震P波层析成像研究巴颜喀拉地块东缘及邻区的深部结构

Deep structure of eastern margin of Bayan Har block and its adjacent areas by using teleseismic P-wave tomography

  • 摘要: 为了揭示巴颜喀拉地块东缘及邻区的壳幔速度结构差异,获取2017年九寨沟MS7.0地震的深部构造背景,本文收集了2009年5月至2016年8月期间四川及邻区数字测震台网的203个地震台站所记录到的远震P波走时数据,应用有限频体波走时层析成像方法,反演得到了巴颜喀拉地块东缘及邻区50—600 km深度范围内的三维壳幔P波速度结构。反演结果表明:巴颜喀拉地块东缘及邻区的壳幔速度结构具有明显的横向不均匀性和分区特征,松潘—甘孜地槽褶皱系、西秦岭和祁连山褶皱系的整体速度异常较低,研究区东部具有克拉通性质的四川盆地西北缘和鄂尔多斯地块南缘则呈明显的高速异常。上地幔P波速度结构特征差异表明松潘—甘孜地块的抬升可能与地幔上涌有关,巴颜喀拉地块东缘九寨沟震区及周边50—250 km深度范围内的上地幔存在低速异常,在400—600 km地幔过渡带深度范围内表现为明显的高速异常特征。巴颜喀拉地块向东南方向运移受到东部高速、高强度的扬子克拉通地块对青藏高原物质东向挤出的强烈阻挡,而九寨沟震区处于松潘—甘孜地块重要的北东边界断裂交会处附近,应力容易在此集中,这些因素均可能是东昆仑断裂塔藏段与岷江断裂北段交会处附近发生九寨沟MS7.0地震的深部动力学背景。

     

    Abstract: This paper collected the teleseismic P-wave travel data recorded by 203 broadband stations in digital seismic network of Sichuan and its neighboring areas from May 2009 to August 2016. And by using the finite-frequency tomography this paper carried out the inversion for P-wave velocity structure of the crust and upper mantle in the depth of 50−600 km in the eastern margin of Bayan Har block and its surrounding areas. The results show that the velocity structure of the Bayan Har block in the eastern part of the Qinghai-Xizang (Tibetan) Plateau and the surrounding crustal-mantle is characterized by obviously lateral inhomogeneity and zoning. Specifically, the Songpan-Garze trough fold system, the western Qinling and Qilianshan fold systems in the eastern margin of the Tibetan Plateau displayed low velocity, whereas the northwestern margin of the Sichuan basin and the southern edge of the Ordos block in the eastern part of the studied area showed obvious high velocity anomalies. P wave velocity structure characteristics of upper mantle suggested that the uplift of Songpan-Garze block is related to upper mantle upwelling. There are low velocity anomalies in the depth range of 50−250 km in Jiu-zhaigou earthquake area and the surrounding upper mantle in the east margin of Bayan Har block. The three-dimensional P-wave velocity structure also reveals that the source region of Jiuzhaigou MS7.0 earthquake shows a high-velocity anomaly at the mantle transition zone with depth range of 400−600 km. Therefore, it was deduced that this anomaly may be caused by upwelling of hot asthenosphere material. With the crustal thickening and strong uplift of the Tibetan Plateau, the Sichuan-Qinghai block in the west of Longmenshan fault zone slipped and was pushed to the SE direction, which was influenced by the blocking of high velocity and high strength craton blocks to the eastern Qinghai-Tibet Plateau extrusion, its hard upper crust should form a huge stress accumulation, and Jiuzhaigou is located in the vicinity of the north-east boundary fault intersection at the Songpan-Garze block, where the stress is likely to be concentrated. These factors may result in the occurrence of the Jiuzhaigou MS7.0 earthquake near the East Kunlun fault zone and the northern section of Minjiang fault.

     

/

返回文章
返回