高原,
中国地震局地震预测研究所(地震预测重点实验室), 北京 100036
基金项目: 国家自然科学基金（41474032）和中国地震局地震预测研究所基本科研业务费专项（2015IES0202，2017IES010202）共同资助
详细信息
作者简介: 王琼, 女, 1986年生, 博士, 助理研究员, 目前从事地震各向异性、噪声成像等方面研究.E-mail:sunny-wangqiong@163.com
通讯作者: 高原, 男, 1964年生, 研究员, 主要从事地震各向异性等地震学基础研究.E-mail:gaoyuan@cea-ies.ac.cn
中图分类号: P315收稿日期:2017-08-24
修回日期:2018-03-22
上线日期:2018-07-05
Rayleigh wave phase velocity and azimuthal anisotropy in the northeastern margin of the Tibetan plateau derived from seismic ambient noise
WANG Qiong,GAO Yuan,
Institute of Earthquake Forecasting, China Earthquake Administration, Beijing 100036, China
More Information
Corresponding author: GAO Yuan,E-mail:gaoyuan@cea-ies.ac.cn
MSC: P315--> Received Date: 24 August 2017
Revised Date: 22 March 2018
Available Online: 05 July 2018
摘要
摘要:本研究收集了甘肃、青海、宁夏等118个宽频带数字地震台站的连续波形资料，利用噪声互相关，经过计算和筛选，在5~38 s范围内，共得到5773条瑞利波相速度频散曲线.然后采用1°×1°的网格划分，反演获得青藏高原东北缘相速度和方位各向异性分布.结果表明：短周期8~12 s内，鄂尔多斯从低速异常变为高速异常；该周期范围内各向异性结果与区域断裂走向有很好的一致性.18~25 s周期内，祁连地块、松潘-甘孜地块、羌塘地块低速异常范围逐渐变大，随周期增加地壳低速异常与人工探测结果相符；鄂尔多斯表现为速度随周期增加逐渐变大，说明其中下地壳速度相对偏高，不存在低速异常；该周期范围内的各向异性特征表现为，祁连地块和松潘甘孜地块大致呈NW-SE方向，而青藏高原内部快波方向显示了顺时针旋转的形态.在30~35 s范围内面波速度主要受莫霍面深度和莫霍面附近介质速度的影响，与地壳厚度分布有非常好的吻合.综合不同方法获得的各向异性研究结果，支持印度-欧亚板块的碰撞使青藏高原东北缘地壳发生缩短和逐渐隆升的观点，认为整个岩石圈的垂直缩短变形是青藏高原东北缘的主要形成机制.
关键词: 青藏东北缘/
背景噪声/
瑞利波/
面波层析成像/
方位各向异性
Abstract:We collected data of continuous seismic waveforms recorded by 118 broadband stations from January 2011 to December 2012. Using cross-correlation, we obtained 5773 Rayleigh wave dispersion curves at periods 5 s to 38 s, and then invert the phase velocity and azimuth anisotropy by a 1°×1° grid. The results show that at short periods of 8~12 s, the phase velocity in Ordos gradually changes from low-velocity anomalies to high anomalies, reflecting the depth of sediments in the Ordos block. The anisotropy in this period range is consistent with the strike of the regional faults. At periods of 18~25 s, the Qilian, Songpan-Garzê and Qiangtang blocks exhibit a large range of low velocity, consistent with the results of deep seismic sounding. The velocity in the Ordos becomes higher with increasing period, implying relatively high velocity in mid-lower crust of the Ordos block. The predominant direction of fast waves in the Qilian and Songpan-Garzê blocks is NW-SE, while there is a clockwise rotation of fast wave direction in the interior of Tibet. At periods of 30~35 s, the phase velocity is mainly influenced by the Moho depth. Combining results of anisotropy from varied methods suggests that the lithospheric deformation in the study area is primarily driven by vertically coherent shortening associated with the India-Asia collision, which causes continuous crustal movement towards northeast, and at the same time blocked by the rigid Siberian platform in northeast.
Key words:Northeastern margin of the Tibetan plateau/
Ambient noise/
Rayleigh wave/
Surface wave tomography/
Azimuthal anisotropy
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