The authors use the shear wave splitting method to calculate the XKS seismic phases recorded by the temporary broadband seismic stations of Peking University, Southern University of Science and Technology and Guilin University of Technology in Guangdong and Guangxi Provinces, and the fixed stations of China Earthquake Administration in Guangdong, Guangxi and Hainan Provinces. The authors obtain the anisotropy parameters of the upper mantle in Hainan and its adjacent areas, and the delay time is between 0.35 and 1.90 s. Based on the previous shear wave splitting results around the research region, the authors believe that with the retreat of the subduction zone of eastern Pacific plate, the asthenosphere material in the west flows eastward to fill, making the olivine lattice of the upper mantle aligned along the E-W direction in most areas of central and northern Guangdong and Guangxi. Because the continental lithosphere at the coastline is thinning rapidly, the splitting results in Guangdong coastal areas are mostly NE-SW direction, parallel to the coastline. In particular, there are several NULL stations in the coastal areas near Hainan Island, and the splitting results in the northeast corner of Hainan Island are very disorderly, with small δt. These observations support that Hainan plume may exist on the southeast of Leizhou Peninsula, which is centered at 20.5°N and 111.5°E.

利用横波分裂方法, 对北京大学、南方科技大学及桂林理工大学在广东和广西布设的宽频带流动台阵以及国家地震台网在广东、广西和海南的固定台站记录的XKS震相进行计算, 得到海南及邻近地区的上地幔各向异性参数, 分裂延迟时间在0.35~1.90 s之间。综合研究区域内前人发表的和本文的横波分裂结果, 认为自新生代以来, 伴随东部太平洋板块俯冲带后撤, 华南地区西部软流圈物质向东流动进行补充, 导致广东及广西的中部和北部大部分地区上地幔橄榄石晶格大体上沿E-W方向定向排列。受控于海岸线处大陆岩石圈迅速减薄, 广东沿海地区横波分裂多数沿NE-SW方向, 与海岸线近似平行。特别是, 海南岛附近沿海地区分布若干显著不具有横波分裂的台站; 海南岛东北角的分裂方向很乱, 且横波分裂快慢波到时差(δt)很小。这些观测结果都支持海南地幔柱可能存在于雷州半岛的东南方向, 大致位于20.5°N, 111.5°E。