Mantle structure and flow beneath the central-western US: Constraints from anisotropic tomography

被引:6
作者
Wang, Xinyang [1 ,4 ]
Zhao, Dapeng [2 ]
Xia, Shaohong [1 ,4 ]
Li, Jiabiao [3 ]
机构
[1] Chinese Acad Sci, South China Sea Inst Oceanol, CAS Key Lab Ocean & Marginal Sea Geol, Guangzhou 510301, Peoples R China
[2] Tohoku Univ, Grad Sch Sci, Dept Geophys, Sendai, Miyagi 9808578, Japan
[3] Minist Nat Resources, Key Lab Submarine Geosci, Inst Oceanog 2, Hangzhou 310012, Peoples R China
[4] Southern Marine Sci & Engn Guangdong Lab Guangzho, Guangzhou 511458, Peoples R China
基金
中国国家自然科学基金; 日本学术振兴会;
关键词
Seismic anisotropy; Anisotropic tomography; Lithosphere; Asthenosphere; Yellowstone hotspot; Earthquake; WAVE AZIMUTHAL ANISOTROPY; SEISMIC ANISOTROPY; P-WAVE; UNITED-STATES; VELOCITY STRUCTURE; SUBDUCTION ZONE; NORTH-AMERICA; GREAT-PLAINS; DEFORMATION; EARTHQUAKES;
D O I
10.1016/j.tecto.2021.229180
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
To investigate lateral and depth variations of seismic anisotropy beneath the central-western United States, we determined a detailed 3-D model of P-wave anisotropic tomography by inverting a large number of arrival-time data of local and teleseismic events. Our results reveal significant azimuthal anisotropies in the crust and lithosphere, which are associated with ancient orogenic collisional and magmatic activities. As depth increases, the fast-velocity direction (FVD) pattern becomes gradually trended and small features fade away. There is a boundary in the FVD distribution, which separates the tectonically active region in the west from the stable cratonic region in the east. Frozen-in anisotropy with a NW-SE FVD is preserved in the thick Wyoming cratonic lithosphere that exhibits as a high-velocity (high-V) anomaly to a depth of similar to 250 km. In the asthenosphere beneath the western thin lithosphere, FVDs are generally parallel with the absolute motion direction of the North American plate due to shearing between the plate and the asthenosphere. In the deeper areas, the subducted and fragmented slab exhibiting as high-V anomalies leads to slab-related mantle flows. These results indicate that seismic anisotropies exist in both the lithosphere and asthenosphere with different geodynamic mechanisms and it is feasible to link the P-wave azimuthal anisotropy to lithospheric deformations, fossil anisotropy in the lithosphere, and flows in the asthenosphere.
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页数:11
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