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利用中国国家测震台网数据对中国大陆下方横波分裂特征的研究
高玲霞, 孙道远
中国科学技术大学
摘要:
本文利用了中国国家台网2015-2019年记录到的地震数据,在统一测量和判定的标准的基础上,通过测量SKS横波分裂参数研究了中国大陆下方的各向异性特征及成因。在中国大陆下方,快波极化方向由中国大陆西部(中国西北及青藏)的近WE转到中部(鄂尔多斯及四川盆地)的近NS向,再到中国东部(华北及华南)近WE向;分裂时间在中国东部较大,约为1.0-1.7秒;而中、西部较小,约为0.6-1.0秒。结合前人对中国大陆地壳各向异性和厚度的研究,我们的结果表明岩石圈和软流圈是中国大陆地区SKS分裂的主要来源。同时,本文通过对比横波分裂的快轴和GPS速度场的方向是否一致,确定了中国大陆下方壳幔耦合与解耦区域。我们发现中国大陆的壳幔耦合区域主要分布在青藏东北缘、鄂尔多斯南缘、华北及华南地区,壳幔解耦区域主要分布在青藏块体东部、天山、鄂尔多斯西缘及云南南部地区。
关键词:  横波分裂  各向异性  SKS震相  壳幔耦合
DOI:
分类号:
基金项目:
Constraining Seismic Anisotropy beneath the mainland China using Shear Wave Splitting data from China National Seismic Network
GaoLingxia, Sun Daoyuan
USTC
Abstract:
In this paper, we use earthquakes recorded by China National Seismic Network from 2015 to 2019 and measure shear wave splitting parameters of SKS to study the anisotropic characteristics beneath the mainland China. The fast direction changes from near WE in the western China (northwest China and Qinghai-Tibet) to near NS in the central China (Ordos and Sichuan-Yunnan), and then turns to near WE in the eastern China (North and South China). The delay times of slow wave in the eastern China are about 1.0-1.7s, which are larger than those in central and western China (about 0.6-1.0s). Together with previous studies on the crustal anisotropy of the mainland China, our results indicate that lithosphere and asthenosphere contribute most observed SKS splitting. Furthermore, we determine the coupling between crust and mantle beneath the mainland China based on whether the fast direction is consistent with the direction of the GPS velocity or not. We find that the crust-mantle coupling regions are mainly at the northeastern margin of Qinghai-Tibet block, the southern margin of Ordos, and North and South China. The decoupling regions are mainly located at the eastern Qinghai-Tibet block, the Tianshan region, the western margin of Ordos, and Yunnan region.
Key words:  shear wave splitting  anisotropy  SKS  crust-mantle coupling