地震研究

利用1976—2020年喜马拉雅东构造结及邻区ML≥2.0地震的震源机制解反演了研究区域的震源应力场,并结合区域GPS应变率场,分析了该区域现今地壳构造变形特征。结果表明:在川滇菱形块体东边界以及块体内部,最大水平应力SHmax方向与GPS主压应变方向基本一致,且方向变化具有一定的连续性,表明此处上地壳浅部与深部受到相同方向的驱动力; 在川滇菱形块体西边界,最大水平应力方向与GPS主压应变呈现出较明显的差异性,分区均值最大可达42°,表明该处上地壳深浅部可能具有不同的驱动机制。

This paper uses the focal mechanism solutions of ML≥2.0 earthquakes from 1976 to 2020 to invert the focal stress field in the Eastern Himalayan Syntaxis and its surrounding areas,and uses the GPS strain rate field to analyze the current crustal deformation in this area.The results show that on the eastern boundary of the Sichuan-Yunnan block and inside the block,the direction of the maximum horizontal stress changes continuously,almost in the same direction as GPS principal compressive strain; this indicates that the shallow and the deep parts of the upper Crust are driven by forces in the same direction.On the western boundary of the Sichuan-Yunnan block,the direction of the maximum horizontal stress differs sharply from the direction of GPS principal compressive strain,and the regional average can reach up to 42°; this indicates that different driving mechanisms exist in the deep and the shallow of the upper Crust.

引言
1 GPS数据与应变率场
2 震源机制解数据与应力反演
3 研究结果
4 讨论
5 结论

图1 喜马拉雅东构造结及其邻区速度场<br/>Fig.1 Velocity field in the Eastern Himalayan Syntaxis and its adjacent areas

图1 喜马拉雅东构造结及其邻区速度场
Fig.1 Velocity field in the Eastern Himalayan Syntaxis and its adjacent areas

图2 喜马拉雅东构造结及其邻区面应变率(a)和最大剪应变率(b)分布<br/>Fig.2 The plane strain rate(a)and the maximum shear strain rate(b)field in the Eastern Himalayan Syntaxis and its adjacent areas

图2 喜马拉雅东构造结及其邻区面应变率(a)和最大剪应变率(b)分布
Fig.2 The plane strain rate(a)and the maximum shear strain rate(b)field in the Eastern Himalayan Syntaxis and its adjacent areas

图3 喜马拉雅东构造结及其邻区震源机制解分布<br/>Fig.3 Distribution of the focal mechanisms in the Eastern Himalayan Syntaxis and its adjacent areas

图3 喜马拉雅东构造结及其邻区震源机制解分布
Fig.3 Distribution of the focal mechanisms in the Eastern Himalayan Syntaxis and its adjacent areas

表1 本文研究震源机制解划分依据<br/>Tab.1 The classification basis of focal mechanisms

表1 本文研究震源机制解划分依据
Tab.1 The classification basis of focal mechanisms

图4 0.5°×0.5°网格地震数目统计(a)及模型拟合曲线图(b)<br/>Fig.4 Statistics of earthquake numbers in 0.5°×0.5° grids(a)and the model's fitting curve(b)

图4 0.5°×0.5°网格地震数目统计(a)及模型拟合曲线图(b)
Fig.4 Statistics of earthquake numbers in 0.5°×0.5° grids(a)and the model's fitting curve(b)

图5 震源应力场反演结果(a)、应力形因子R与最大水平应力SHmax分布结果(b)<br/>Fig.5 Results of stress field inversion in the Eastern Himalayan Syntaxis and its adjacent areas(a) and R-value and the maximum horizontal compressive stress(b)

图5 震源应力场反演结果(a)、应力形因子R与最大水平应力SHmax分布结果(b)
Fig.5 Results of stress field inversion in the Eastern Himalayan Syntaxis and its adjacent areas(a) and R-value and the maximum horizontal compressive stress(b)

图6 GPS主压应变率方向与最大水平应力<br/>SHmax方向对比<br/>Fig.6 Comparison of GPS direction of main compressive strain rate and the direction of maximum horizontal stress

图6 GPS主压应变率方向与最大水平应力
SHmax方向对比
Fig.6 Comparison of GPS direction of main compressive strain rate and the direction of maximum horizontal stress

图7 GPS主压应变方向与最大水平应力SHmax方向夹角统计(a)、分区夹角均值(b)<br/>Fig.7 Statistics of the angle between the direction of GPS main compressive strain and the direction of maximum horizontal stress(a)and mean value of the angle between each partition(b)

图7 GPS主压应变方向与最大水平应力SHmax方向夹角统计(a)、分区夹角均值(b)
Fig.7 Statistics of the angle between the direction of GPS main compressive strain and the direction of maximum horizontal stress(a)and mean value of the angle between each partition(b)

图8 喜马拉雅东构造结及其邻区地壳变形模式的示意图<br/>Fig.8 Schematic diagram of crustal deformation model in the Eastern Himalayan Syntaxis and its adjacent areas

图8 喜马拉雅东构造结及其邻区地壳变形模式的示意图
Fig.8 Schematic diagram of crustal deformation model in the Eastern Himalayan Syntaxis and its adjacent areas

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备注

引言

1 GPS数据与应变率场

2 震源机制解数据与应力反演

3 研究结果

4 讨论

5 结论

期刊信息