SEISMOLOGY AND GEOLOGY ›› 2017, Vol. 39 ›› Issue (1): 130-146.DOI: 10.3969/j.issn.0253-4967.2017.01.010

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THREE-DIMENSIONAL S-WAVE VELOCITY DISTRIBUTION BASED ON AMBIENT NOISE ANALYSIS IN EASTERN NORTH

GONG Meng1,2, XU Xi-wei1, ZHANG Xin-dong3, OUYANG Long-bin4, JIANG Guo-yan1, DONG Bo5   

  1. 1. Key Laboratory of Active Tectonics and Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China;
    2. Earthquake Administration of Hebei Province, Shijiazhuang 050021, China;
    3. Handan Seismostation of Earthquake Administration of Hebei Province, Handan 050061, China;
    4. Earthquake Administration of Guandong Province, Guangzhou 510070, China;
    5. Hebei GEO University, Shijiazhuang 050021, China
  • Received:2015-01-20 Revised:2016-11-22 Online:2017-02-20 Published:2017-04-26

华北东部基于背景噪声的壳幔三维S波速度结构

宫猛1,2, 徐锡伟1, 张新东3, 欧阳龙斌4, 江国焰1, 董博5   

  1. 1. 中国地震局地质研究所, 活动构造与火山重点实验室, 北京 100029;
    2. 河北省地震局, 石家庄 050021;
    3. 河北省地震局邯郸中心台, 邯郸 056001;
    4. 广东省地震局地震监测中心, 广州 510070;
    5. 河北地质大学, 石家庄 050021
  • 作者简介:宫猛,男,1983年生,博士研究生在读,构造地质学专业,主要从事数字地震学及地震活动性分析研究工作,E-mail:mrgongm@163.com
  • 基金资助:

    国家自然科学基金(91214201)、晋冀蒙交界地区临时台网架设运行维护及地震危险性和对策研究(DZ20150428102)与中国地震局震情跟踪课题(2016010119)共同资助

Abstract:

We apply ambient noise tomography to continuous vertical component broadband seismic data between January 1, 2010 and December 31, 2011from the regional networks of 190 stations deployed by China Earthquake Administration in Hebei, Shanxi and Inner Mengolia. Ambient noise cross-correlations were performed to produce the Green's functions of each station-pair. Firstly, we used the multiple-filter analysis method to extract surface wave group and phase velocity dispersion curves from inter-station paths at periods from 7 to 40s. Then the study area was discretized into a 0.2°×0.2° grid to obtain the group and phase velocity distributions using O'ccam inversion method. After that, three dimensional (3-D) S-wave velocity structures from the surface down to 50km are inverted from group and phase velocities dispersion results. the results of S wave velocity distribution maps generally demonstrate good correlations with surface geological and tectonic features, and they also clearly revealed the lateral velocity variation in the crust. In the mid-upper crust, the basins are clearly resolved with low S wave velocity due to its thick sedimentary layer, and the Taihang and Yanshan uplifts show relative higher S wave velocity distribution. With the increase of depth (>30km), the S wave velocity distribution presents a contrary characteristic compared to that of the shallow layer, and the S wave velocity beneath the Taihang and Yanshan uplifts are much lower than basin areas, which is possibly correlated with the thickness of the crust. 3-D S wave velocity shows a low-velocity zone at~10~20km depth observed beneath the Tanshan-Hejian-Xintai-Cixian belt and Bohai Bay. the low-velocity zone at~20~30km depth beneath the Datong area may be associated with the thermal material in the crust-mantle. Our S wave velocity distribution maps clearly show that Taihang Mountains is not only the boundary of topography and tectonic zone, but also the transition zone of high and low S wave velocity.

Key words: ambient noise, dispersion curve, S wave, crustal and uppermost mantle structure

摘要:

收集了华北东部地区的190个宽频地震仪记录的自2010年1月至2011年12月共24个月的垂直分量(Z分量)连续噪声数据,采用FTAN(Frequency-Time Analysis)方法从15700多条台站对路径中提取可用的面波群速度和相速度频散曲线,将研究区域划分为0.2°×0.2°的网格,利用O'ccam方法反演得到研究区内7~40s周期内的面波群速度和相速度分布。然后,使用面波在各个网格节点下方的纯路径频散反演研究区一维S波速度结构,再通过线性插值获取了华北东部地区的三维S波速度结构。结果显示S波速度分布特征与地表地质和构造特征表现出较好的相关性,能清晰地揭示出地壳内部的横向速度变化;在中上地壳(深度<25km),拥有较厚沉积层的华北盆地和分布在山间的第四纪沉积盆地表现为低速特征,而基岩广泛出露的太行山和燕山隆起区呈现出大面积的高速异常;随着深度的增加(>30km),下地壳-上地幔顶部的S波分布特征呈现出与浅部相反的特性,拥有较薄地壳的华北盆地表现为高速,而拥有较厚地壳的太行山及燕山隆起区S波速度相对较低。三维S波速度剖面结果显示:华北平原带的唐山-河间-邢台-磁县一线和渤海湾地下10~20km存在低速异常区。大同地区地下20~30km的S波速度出现低微的速度逆转可能与该区壳-幔的热物质分布相联系。S波速度分布显示,太行山不仅是华北平原与太行山的地形和构造分界带,同时也是1个明显的速度转换带。

关键词: 背景噪声, 频散曲线, S波速度, 壳-幔结构

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