期刊
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
卷 120, 期 7, 页码 5154-5174出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/2015JB012098
关键词
seismic tomography; azimuthal anisotropy; subduction; Hainan plume; Tibetan Plateau
资金
- National Natural Science Foundations of China [41204040, 41374048]
- China National Special Fund for Earthquake Scientific Research in Public Interest [201008001]
- JSPS [Kiban-S 11050123]
- MEXT [26106005]
- Grants-in-Aid for Scientific Research [23224012] Funding Source: KAKEN
Southeast Asia is surrounded by subduction zones resulting from the interactions of several lithospheric plates. Its evolution has been also influenced by active tectonics due to the Indo-Asian collision in the Cenozoic. In this study, we use a large number of arrival-time data of local and regional earthquakes to determine 3-D P wave tomography and azimuthal anisotropy in the mantle beneath SE Asia. High-velocity (high-V) anomalies representing the subducting slabs are clearly visible in the upper mantle and the mantle transition zone (MTZ). Low-velocity (low-V) zones with trench-normal anisotropy are revealed in the uppermost mantle, which indicate back-arc spreading or secondary mantle-wedge flow induced by the slab subduction. In contrast, trench-parallel anisotropy dominates in the deep upper mantle and reflects structures either in the subducting slab or in the upper mantle surrounding the slab. The trench-parallel anisotropy is also significant in the lower MTZ, which may contribute to shear wave splitting observations. A low-V body extending down to the lower mantle is visible under the Hainan volcano far away from the plate boundaries, suggesting that Hainan is a hot spot fed by a lower-mantle plume. The low-V body under Hainan is connected with low-V zones in the upper mantle under SE Tibet and Vietnam. Our P wave anisotropy results reflect significant mantle flow existing in the asthenosphere from SE Tibet to Hainan and further southwestward to Vietnam. The present study, especially the 3-D P wave anisotropy results, provides important new insight into mantle dynamics in SE Asia.
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