利用GRACE时变重力场反演青藏高原的隆升速率

Uplift rate of the Tibetan Plateau constrained by GRACE time-variable gravity field

青藏高原隆升对中国、亚洲乃至世界的气候都有着重要影响,研究青藏高原地壳隆升速率具有重大意义.本文利用2004—2015年期间高覆盖度的卫星重力数据,通过去除陆地储水的重力效应获得地壳隆升引起的重力变化速率,基于直立长方体垂直运动与重力变化的关系模型反演了该区域的地壳隆升速率分布.研究结果表明在300 km的空间尺度下青藏高原隆升速率分布具有不均匀的特点,表现为以冈底斯山—唐古拉山—鲜水河断裂带为界线,其两侧的速率差异较大.位于界线以南,沿喜马拉雅推覆构造带的区域平均隆升速率为2.01±0.87 mm·a^-1,其中西侧的印度板块与东侧的缅甸板块隆升速率分别为~2.43 mm·a^-1、~2.89 mm·a^-1,位于两板块之间的区域隆升速率为~0.69 mm·a^-1;位于界线以北,除了天山区域和华北板块的隆升速率为~1 mm·a^-1,其他区域隆升现象不明显,其速率为~0 mm·a^-1.我们发现存在两条均穿过正断裂带区域的隆升速率梯度带,其中一条为从加德满都到塔里木盆地,其恰好穿过青藏高原内部的正断裂带,另一条为从那加山到四川盆地,其恰好穿过大理正断裂带.本文反演的青藏高原隆升速率与以往观测到的GPS结果有很好的一致性,为青藏高原隆升、地壳增厚等科学问题提供理论支持.

The uplift of the Tibetan Plateau(TP)has an important impact on the climate of China,Asia and the world.It is of great significance to study the crustal uplift rate of the TP.In this paper,using the gravity data of satellites with high coverage from 2004 to 2015,the rate of gravity change caused by crustal uplift is obtained by removing the gravity effect of land water storage.The distribution of crustal uplift rate is inversed based on the model between vertical deformation of vertical cuboid and gravity change on the TP.The results of the study show that the uplift rate of the TP is unevenly distributed at a spatial scale of 300 km.With the Gangdise-Tanggula Mountain-Xianshuihe River fault as the boundary,the uplift rate on both sides is quite different.To the south of the borderline,the average uplift rate of the area along the Himalayan thrust nappe belt is 2.01±0.87 mm·a^-1,in which the uplift rates of the Indian Plate on the west and the Myanmar Plate on the east are 2.43 mm·a^-1 and 2.89 mm·a^-1,respectively.The uplift rate of the area between the two plates is about 0.69 mm·a^-1.To the north of the borderline,except for the Tianshan area and the North China Plate,the uplift rate is about 1 mm·a^-1,the rate is close to 0 mm·a^-1.We found that both the rate gradient zones of uplift pass through the normal fault zone,one of which is from Kathmandu to the Tarim Basin and happens to pass through the normal fault zone inside the TP,the other of which is from the Naga Mountains to the Sichuan Basin and happens to be cross the Dali normal fault zone.The inversion rate of the uplift is in good agreement with the previous GPS observations,providing theoretical support for scientific issues such as uplift of the TP and crustal thickening of the crust.