Crustal structure across the NE Tibetan Plateau and Ordos Block from the joint inversion of receiver functions and Rayleigh-wave dispersions
Crustal structure across the NE Tibetan Plateau and Ordos Block from the joint inversion of receiver functions and Rayleigh-wave dispersions
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接收函数和瑞利波色散联合反演青藏高原东北部和鄂尔多斯地块的地壳结构
DOI：
10.1016/j.tecto.2017.03.020
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发表时间：
2017
期刊：
影响因子：
2.9
通讯作者：
Ding Zhifeng
中科院分区：
文献类型：
--
作者：
Li Yonghua;Wang Xingchen;Zhang Ruiqing;Wu Qingju;Ding Zhifeng
我们使用 H-κ 叠加方法以及瑞利波相位和群速度联合反演接收函数，研究了 34 个站点的地壳结构。这些地震台分布在松潘-甘孜地体、秦岭-祁连地体和鄂尔多斯盆地西南部的剖面上。我们的结果揭示了该剖面上地壳厚度的变化。我们在松潘-甘孜地体（47-59 km）下方发现了厚的地壳，在西秦岭和祁连地体中减少到~ 45-47 km，并在西南鄂尔多斯地块（43-51 km）下方达到局部最小值，平均地壳厚度为 46.7 ± 2.5 km。在西藏东北部的大部分台站下方都发现了上地壳的低速带，这可能表明存在部分熔融或弱拆离层。我们对低至中等 Vp/Vs (1.67–1.79) 的观察结果代表了长英质至中等地壳成分。通过联合反演估计的剪切速度模型还揭示了剖面下方速度的显着横向变化，这主要反映在下地壳速度上。对于鄂尔多斯地块，20 km 以下的平均剪切波速度约为 3.8 km/s，表明下地壳为中长英质。厚的青藏高原东北地壳的特征是20 km以下的慢横波速度（3.3-3.6 km/s），下地壳缺乏高速物质（Vs≥4.0 km/s），这可能归因于镁铁质下地壳拆沉或/和上地壳和中地壳的增厚。
We investigated the crustal structure at 34 stations using the H-κ stacking method and jointly inverting receiver functions with Rayleigh-wave phase and group velocities. These seismic stations are distributed along a profile extending across the Songpan-Ganzi Terrane, Qinling-Qilian terranes and southwestern Ordos Basin. Our results reveal the variation in crustal thickness across this profile. We found thick crust beneath the Songpan-Ganzi Terrane (47–59 km) that decreases to ~ 45–47 km in the west Qinling and Qilian terranes, and reaches its local minimum beneath the southwestern Ordos Block (43–51 km) at an average crustal thickness of 46.7 ± 2.5 km. A low-velocity zone in the upper crust was found beneath most of the stations in NE Tibet, which may be indicative of partial melt or a weak detachment layer. Our observations of low to moderate Vp/Vs (1.67–1.79) represent a felsic to intermediate crustal composition. The shear velocity models estimated from joint inversions also reveal substantial lateral variations in velocity beneath the profile, which is mainly reflected in the lower crustal velocities. For the Ordos Block, the average shear wave velocities below 20 km are ~ 3.8 km/s, indicating an intermediate-to-felsic lower crust. The thick NE Tibet crust is characterized by slow shear wave velocities (3.3–3.6 km/s) below 20 km and lacks high-velocity material (Vs ≥ 4.0 km/s) in the lower crust, which may be attributed to mafic lower crustal delamination or/and the thickening of the upper and middle crust.