摘要
位于喜马拉雅东构造结核心地带的南迦巴瓦构造结,地处欧亚板块、印度板块与缅甸地块3大构造单元的交汇区域。该区域不仅是青藏高原东南向侧向走滑挤出变形及板块边界走向发生90°转折的关键构造节点,更是构造应力最为集中、隆升速率最快且剥蚀作用最为强烈的典型区域。对这一特殊构造区域速度结构的深入研究,将为揭示地震孕育机制等科学问题提供重要的参考依据。本研究基于2020年6月14日至7月24日布设在南迦巴瓦地区374台短周期节点地震仪组成的密集台阵数据,联合2009年至2024年期间的区域测震台网资料,利用双差层析成像方法获得该区域及其附近地区的速度结构以及地震精定位结果。结果表明:南迦巴瓦峰北侧和东侧位于高速异常区,而西南侧位于低速异常区;在分辨率较高的10 km深度处,嘉黎断裂中段位置的P波速度结构有所变化,由高速异常特征转为低速异常;P波和S波的速度异常(高速与低速区)的延伸方向与研究区主干断裂的走向高度匹配;从5 km深度起,南迦巴瓦构造结及其附近地区呈现低波速比特征,且随深度增加,该现象更为显著。
The Namche Barwa massif is located in the core area of the eastern Himalayan syntaxis.This area is located at the junction of the Eurasian plate,Indian plate and Myanmar block.It is the key part of the southeastward lateral strike-slip extrusion and 90°deflection of the plate boundary on the Tibetan Plateau.It is also the region with the strongest tectonic stress and the fastest uplift rate and denudation.It is of great significance to study the velocity structure of this area to understand the mechanism of earthquake preparation.On the basis of the dense array data of 374 short-period nodal seismometers deployed in the Namche Barwa area between June 14 and July 24,2020,in combination with the data of the regional seismic network from 2009 to 2024,the double-difference tomography method was used in this study to obtain the velocity structure characteristics and precise relocation of earthquake results of Namche Barwa and its vicinity.The results show the north and east sides of the Namche Barwa peak are located in the high-velocity anomaly area,whereas the southwest side is located in the low-velocity anomaly area.At a depth of 10km with high resolution,the P-wave velocity structure in the middle section of the Jiali fault changed from high-velocity anomaly to low-velocity anomaly.The trend of P-wave and S-wave high-velocity and low-velocity anomaly areas is consistent with the trend of the main active fault zones.From a depth of 5km,the wave velocity ratio of the Namche Barwa massif and its vicinity is low,and the phenomenon is more significant with the increase in depth.
作者
李敏娟
沈旭章
马海萍
刘白云
宋婷
刘谨瑞
谭家炜
陈枭
窦喜英
LI Minjuan;SHEN Xuzhang;MA Haiping;LIU Baiyun;SONG Ting;LIU Jinrui;TAN Jiawei;CHEN Xiao;DOU Xiying(Gansu Earthquake Agency,Lanzhou 730000,China;School of Earth Sciences and Engineering,Sun Yat-sen University,Zhuhai 519000,China;Lanzhou Petrochemical Vocational and Technical University,Lanzhou 730060,China)
出处
《CT理论与应用研究(中英文)》
2025年第5期790-802,共13页
Computerized Tomography Theory and Applications
基金
国家自然基金重点项目(祁连造山带深部结构与晚新生代构造变形研究(42230305))
第二次青藏高原综合科学考察研究(关键地区岩石圈精细结构与浅部响应(20190 ZKK0701))
中央级公益性科研院所基本业务费专项(2023年甘肃积石山Ms6.2地震上地壳P波速度结构分析与深部孕震环境研究(LISCEA202401))
中央级公益性科研院所基本业务费专项(两次门源强震前后冷龙岭断裂变形特征研究(LISCEA202402))
地震监测预报预警工作任务(地震精定位结果自动产出流程研发——以积石山6.2级地震为例(CEA-ZQGZ-202501047))
2022年度甘肃省高等学校创新基金(中强地震危险性综合概率评估系统研发及应用——以甘肃地区为例(2022A-213))。
关键词
南迦巴瓦构造结
双差层析成像
三维速度结构
米林地震
The Namche Barwa massif
double-difference tomography
three-dimensional velocity structure
milin earthquake
