Upper mantle beneath Southeast Asia from S velocity tomography
Upper mantle beneath Southeast Asia from S velocity tomography
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DOI：
10.1029/2000jb000073
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发表时间：
2003
影响因子：
--
通讯作者：
S. Lebedev;G. Nolet
中科院分区：
文献类型：
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作者：
S. Lebedev;G. Nolet
[1]我们提出了一个三维的，S速度模型的东南亚-西太平洋上地幔与400公里的横向分辨率。使用新的自动多模反演技术，我们处理了4038个垂直分量地震记录，并提取了22,708个线性方程，这些方程具有约束上地幔结构的不相关不确定性。我们使用时频窗来选择散射能量比例可以忽略不计的信号。该窗口包括基本瑞利模式和S波和多次S波。在地幔上部150 km处，观测到的S波速度变化幅度最大（17-18%）。高速大陆根可以延伸到目前覆盖太古代-元古代地壳的范围之外500公里。在前寒武纪的某些单元之下，根是不存在的，这可以归因于古岩石圈的变形和逐渐破坏。在120-150公里处，某些日冕下方的S速度达到4.8公里/秒;这可以由热效应和成分效应来解释。在海南岛地区下方，从近地表到模式底部观察到低速异常，这里的热点型火山活动可能是由深部地幔海南柱引起的。低速地幔域位于日本海中南部，表面被板内火山所包围。在40°N附近的太平洋板块俯冲下存在一个深地震活动空区，可能是地幔柱-板块相互作用的结果。在扬子江北方边界之下的过渡带存在一个高速异常。我们建议，异常对应于俯冲大陆岩石圈，停滞在660公里的不连续顶部。
[1] We present a three-dimensional, S velocity model of the SE Asian-western Pacific upper mantle with 400-km lateral resolution. Using the novel Automated Multimode Inversion technique, we processed 4038 vertical-component seismograms and extracted 22,708 linear equations with uncorrelated uncertainties that constrain upper mantle structure. We used time-frequency windows to select signal with negligible proportion of scattered energy. The windows included the fundamental Rayleigh mode and S and multiple S waves. The observed range of S velocity variations is the widest (17–18%) in the upper 150 km of the mantle. High-velocity continental roots can reach beyond the present extent of the overlying Archean-Proterozoic crust by 500 km. Beneath some Precambrian units the roots are absent, which can be attributed to deformation and gradual destruction of the ancient lithosphere. At 120–150 km, S velocity beneath some cratons reaches 4.8 km/s; this can be accounted for by thermal and compositional effects. Beneath the Hainan Island area a low-velocity anomaly is observed from near the surface to the bottom of our model; the hot spot-type volcanism here may be caused by the deep-mantle Hainan plume. A low-velocity mantle domain underlies the south central Sea of Japan, surrounded on the surface by intraplate volcanoes. A deep-seismicity gap is present near 40°N in the Pacific slab subducting below and may result from a plume-slab interaction. A high-velocity anomaly is present in the transition zone beneath the northern boundary of the Yangtze Craton. We propose that the anomaly corresponds to subducted continental lithosphere, stagnant atop the 660-km discontinuity.