摘要
中缅边界地区位于缅甸弧东缘—青藏高原东南缘—巽他板块的衔接地带,地质构造复杂,区内多条活动断裂横跨中缅两国.为了研究中缅边界地区现今地壳形变特征,本文收集处理1998至2020年中国和缅甸的GPS数据,获得了中缅边界地区高空间分辨率的GPS速度场,并采用多尺度球面小波方法计算了多尺度应变率场.结果表明:(1)印度板块向缅甸块体东侧强烈挤压俯冲作用导致位于缅甸弧的GPS测站以约30 mm/a的速度沿NNE向随着印度板块向青藏高原推挤,缅甸弧地区剪切应变积累明显,主压应变率在弧外侧表现为垂直构造走向的近东西向挤压,在弧内侧与伊洛瓦底江盆地表现为平行构造的近南北向挤压.实皆断裂处于主应变率与剪应变率的高值区,存在分段活动性:北段两侧的速度呈现明显的差异,剪切应变积累显著,呈现右旋剪切运动和缩短;中段以约20 mm/a的速度向NNW向运动,具有右旋走滑兼拉张特征.(2)川滇块体围绕东喜马拉雅构造结顺时针旋转,GPS速度方向从构造结北侧的近东西向运动偏转到川滇菱形块体为向南或东南运动,并在滇西南地区呈弥散型分布,速率向东南逐渐减小.其中,小江断裂带总体为左旋走滑.红河断裂中段具有较低的走滑速率,而北段和南段具有较高的剪切速率.大盈江断裂呈现出东西向拉张的特点,表现出明显的左旋走滑特征.龙陵—瑞丽断裂呈右旋走滑兼拉张特征.南汀河断裂、孟连断裂、景洪—打洛断裂等均处于低剪切状态,以左旋走滑为主.西北—东南走向的澜沧断裂、无量山断裂则表现出右旋走滑特征,北西走向的龙陵—澜沧断裂带表现为右旋走滑为主兼具拉张性质.(3)实皆断裂、畹町断裂、南汀河断裂、无量山断裂中部等地区应变积累较快,其地震危险性值得关注.本研究对于认识中缅边界地区的构造动力学特征,评估该区的地震灾害具有科学意义和现实需求.
The region along the border between China and Myanmar is situated at the intersection of the eastern edge of the Myanmar arc,the southeast edge of the Qinghai Tibet Plateau,and the Sunda Plate.This region is characterized by its complex geological structure and strong tectonic activity.To investigate the contemporary pattern of crustal deformation and the tectonics of the border region,the entire regional GNSS network data from 1998 to 2020 in both countries were analyzed.The multi-scale spherical wavelet algorithm was used to estimate the regional strain rate field for the crust deformation and earthquake risk.The following key findings were obtained:(1)The strong compression and subduction of the Indian plate towards the eastern side of the Myanmar block has caused the GPS stations on the Myanmar arc to move towards the Qinghai-Tibet Plateau in the direction of the Indian plate,at a rate of approximately 30 mm/a.The shear strain accumulation is evident in the Myanmar arc region.The primary compressive stress in the Myanmar arc is nearly east-west compression with a vertical tectonic trend on the outer side of the arc and nearly south-north compression with a parallel structure on the inner side of the arc and the Irrawaddy River basin.The Sagaing fault is situated in a region of high principal and shear strain rates,and its subsection activity has been observed.Significant velocity differences exist between the two sides of the northern segment,with significant shear strain accumulation indicating dextral shear movement and shortening.The middle segment of the Sagaing fault moves towards NNW at a rate of approximately 20 mm/a,characterized by dextral strikeslip movement and tension.(2)The Sichuan-Yunnan block rotates clockwise around the eastern Himalayan tectonic belt,with the GPS velocity direction deflecting from the nearly east-west movement on the northern side of the Himalayan tectonic knot towards the Sichuan-Yunnan rhombus block moving southward or southeastward.The pattern of velocity distribution in the southwestern part of Yunnan is dispersed,with the rate gradually decreasing in a southeastward direction.The Xiaojiang fault zone is generally characterized by sinistral strike-slip movement.The middle segment of the Honghe fault has a low strike-slip rate,while the north and south segments have high shear rates.The Dayingjiang fault in southwestern Yunnan exhibits characteristics of east-west extension and an apparent sinistral strike-slip trend.The Longling-Ruili fault is characterized by dextral strike-slip movement and extension.The NE-trending Nantinghe fault,Menglian fault,and Jinghong-Daluo fault are in a low shear state and are dominated by left lateral strike-slip movement.The NW-SE-trending Lancang fault and Wuliangshan fault are characterized by dextral strike-slip movement,while the NW-trending Longling-Lancang fault zone is characterized by dextral strike-slip movement and tension.The magnitude of the strain rate accumulation is related to seismic activity.(3)Based on these findings,it is important to pay attention to the future seismic risk associated with the Sagaing fault,Wanding fault,Nantinghe fault,and the middle part of Wuliangshan fault,all of which are located in the high strain rate area.The results of this study are of great significance for earthquake disaster assessment and furthering our understanding of the tectonic dynamic characteristics of the borderland between China and Myanmar.
作者
邹芳
孟国杰
吴伟伟
Myo Thant
赵倩
赵国强
Zou Fang;Meng Guojie;Wu Weiwei;Myo Thant;Zhao Qian;Zhao Guoqiang(School of Civil and Transportation Engineering,Guangdong University of Technology,Guangzhou 510006;China 2 Key Laboratory of Earthquake Prediction,Institute of Earthquake Forecasting,CEA,Beijing 100036;China 3 Department of Geology,Yangon University,Yangon 11041,Myanmar)
出处
《地球与行星物理论评（中英文）》
2023年第6期587-599,共13页
Reviews of Geophysics and Planetary Physics
基金
国家重点研发计划资助项目(2019YFE0108900)
国家自然科学基金面上资助项目(41874024,42274017)
国家自然科学青年基金资助项目(42204012)
中国地震局地震预测研究所基本科研业务费专项(CEAIEF20220404)。
关键词
中缅边界地区
地壳形变
GPS融合速度场
应变积累
构造活动
borderland of China and Myanmar
contemporary crust deformation
merged GPS velocity field
strain buildup
tectonics
