近日，美国加州大学伯克利分校Frederik Link团队报道了地震各向异性揭示印度洋岩石圈地幔驱动的扩散变形。2026年3月30日出版的《地质学》杂志发表了这项成果。

印度洋底大范围的弥散变形带标志着印度板块、卡普里科恩板块和澳大利亚板块交汇的边界区域。针对这一变形机制，已有两种假说被提出：(1) 青藏高原隆升导致汇聚速度减缓；(2) 软流圈流动驱动卡普里科恩板块向东推挤。若仅有第一种机制起作用，印度洋下的地幔剪切方向应与绝对板块运动方向一致；而第二种假说则预测以东西向剪切为主。

研究组利用经海底反射后由P波转换为S波的震相，确定了印度洋下方地幔剪切的方向。快波偏振方向反映了变形取向：在九十度海岭以西呈东西向排列，而在海岭附近则转为与绝对板块运动方向平行。由此推断，前人提出的与留尼汪热点相关的区域性东向软流圈流动可延伸至九十度海岭。这些观测结果表明，东向的地幔流动驱动了卡普里科恩板块，使其与相邻板块产生差异运动，进而引发弥散型的海底变形。

附：英文原文

Title: Mantle-driven diffuse deformation of the Indian Ocean lithosphere revealed by seismic anisotropy

Author: Jonathan Wolf, Frederik Link

Issue&Volume: 2026-03-30

Abstract: Broad zones of diffuse deformation across the Indian Ocean floor mark the boundary region where the Indian, Capricorn, and Australian plates meet. Two hypotheses have been proposed to explain this deformation: (1) a slowdown in convergence due to the uplift of the Tibetan Plateau, and (2) an eastward push of the Capricorn plate driven by asthenospheric flow. If only the first mechanism were active, mantle shear beneath the Indian Ocean would be expected to align with absolute plate motion (APM), whereas the second hypothesis predicts predominantly east-west shear. Here we use P waves that convert to S upon surface reflection to determine the direction of mantle shear beneath the Indian Ocean. Fast polarization directions, which reflect the orientation of deformation, are east-west-aligned just west of the Ninetyeast Ridge and rotate parallel to APM near the ridge. We infer that previously proposed broad eastward asthenospheric flow associated with the Réunion hotspot extends to the Ninetyeast Ridge. These observations suggest eastward-directed mantle flow that drives the Capricorn plate, causing differential motion to neighboring plates, and leading to diffuse seafloor deformation.

DOI: 10.1130/G54375.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G54375.1/727990/Mantle-driven-diffuse-deformation-of-the-IndianredirectedFrom=fulltext