基于祁连山地区78个地震台站的垂直分量连续波形记录，计算台站对之间背景噪声的互相关函数，并叠加得到5-10 s和10-20 s两个周期的瑞利面波信号。利用归一化振幅方法，分析不同周期范围的噪声源能量在不同方位随季节变化的规律。研究结果显示：祁连山地区5-10 s周期背景噪声的能量优势来源，夏季集中在110°-170°方位，冬季集中在300°-350°方位，但在110°-150°方位也有相对微弱的能量分布，表明第二微震带的噪声能量来源在夏季主要来源于太平洋的海洋活动，冬季主要来源于大西洋的海洋活动；10-20 s周期背景噪声的能量优势来源在夏季集中在70°-150°和170°-230°方位，在冬季则集中在290°-350°和70°-130°方位，表明第一微震带的噪声能量在夏季主要来源于印度洋的海洋区域，冬季主要来源于北大西洋和太平洋。由于2个周期的背景噪声源在祁连山地区存在明显的季节差异，因此在利用背景噪声方法研究该地区介质速度结构时，需充分考虑噪声源非均匀性产生的影响。
Based on the continuous wave records of the vertical component of 78 stations of the seismic array in the Qilian Mountains region, the cross-correlation functions of background noise for each station-pair is calculated and the Rayleigh surface wave signals with periods of 5-10 s and 10-20 s are obtained by superposition. The seasonal variation law of noise source energy in different directions for different periods is analyzed and studied by the method of normalized amplitude. The results show that the dominant energy source of 5-10 s period background noise in the Qilian Mountain area is from 110° to 170° in summer, and from 300° to 350° in winter, but there is also a relatively weak energy distribution in 110° to 150° direction, so it indicates that the second microseismic belt mainly comes from the ocean activity in the Pacific Ocean in summer and from the ocean activity in the Atlantic Ocean in winter. The dominant energy sources of 10-20 s periodic background noise are 70° -150° and 170°-230° in summer, and 290°-350° and 70° -130° in winter. The noise energy of the first microseismic belt mainly comes from the sea area of the Indian Ocean in summer and North Atlantic and Pacific in winter. Because the ambient noise source of these two periods has an obvious seasonal variation in the Qilian Mountain area, the influence of inhomogeneity of noise sources should be taken into consideration when the method of ambient noise is used to study the seismic velocity structure in the region.
2020,41(5): 56-62 收稿日期：2020-04-20
DOI：10.3969/j.issn.1003-3246.2020.05.008
基金项目：中国地震局地震预测研究所基本科研业务费专项（项目编号：2017IESLZ08）和中国地震局地震科技星火计划（项目编号：XH20060）；宿迁市防震减灾“十三五”发展规划重大课题研究（项目编号：S201509）
作者简介：郭瑛霞(1990-),女,助理工程师,主要从事地震监测研究工作。E-mail:gyx15230649229@163.com
*通讯作者：张元生(1965-),男,研究员,主要从事地震学和卫星遥感应用研究工作。E-mail:zhangys@gssb.gov.cn
参考文献：
顾勤平,丁志峰,康清清,等. 郯庐断裂带中南段及邻区基于背景噪声的瑞利波群速度层析成像[J]. 地球物理学报,2020,63(4):1505-1522.
马小军,马禾青,李军,等. 青藏高原东北缘背景噪声特征分析[J]. 地震研究,2014,37(4):607-613.
王伟涛,杨润海,郑定昌,等. 云南地区背景噪声互相关函数中体波信号来源初探[J]. 地震研究,2011,34(3):350-357.
徐果明,李光品,王善恩,等. 用瑞利面波资料反演中国大陆东部地壳上地幔横波速度的三维构造[J]. 地球物理学报,2000,43(3):366-376.
Bensen G D, Ritzwoller M H, Barmin M P, et al. Processing seismic ambient noise data to obtain reliable broad-band surface wave dispersion measurements[J]. Geophysical Journal International, 2007, 169(3):1239-1260.
Claerbout J F. Synthesis of a layered medium from its acoustic transmission response[J]. Geophysics, 1968, 33(2):264-269.
Duvall T L Jr, Jefferies S M, Harvey J W, et al. Time-distance helioseismology[J]. Bulletin of the American Astronomical Society, 1993, 25:1220.
Kedar S, Longuet-Higgins M, Webb F, et al. The origin of deep ocean microseisms in the North Atlantic Ocean[J]. Proc R Soc A, 2007, 464(2091):777-793.
Lin F C, Moschetti M P, Ritzwoller M H. Surface wave tomography of the western United States from ambient seismic noise:Rayleigh and Love wave phase velocity maps[J]. Geophysical Journal International, 2008, 173(1):281-298.
Lobkis O I, Weaver R L. On the emergence of the Green's function in the correlations of a diffuse field[J]. Journal of the Acoustical Society of America, 2001, 110(6):3011-3017.
Paul A, Campillo M, Margerin L, et al. Empirical synthesis of time-asymmetrical Green functions from the correlation of coda waves[J]. Journal of Geophysical Research:Solid Earth, 2005, 110(8):B08302.
Rhie J, Romanowicz B. Excitation of Earth's continuous free oscillations by atmosphere-ocean-seafloor coupling[J]. Nature, 2004, 431(7008):552-556.
Roux P, Sabra K G, Gerstoft P, Kuperman W A, Fehler M C. P-waves from cross-correlation of seismic noise[J]. Geophys Res Lett, 2005, 32(19):L19303, doi:10.1029/2005GL023803.
Stehly L, Campillo M, Shapiro N M. A study of the seismic noise from its long-range correlation properties[J]. Journal of Geophysical Research:Solid Earth, 2006, 111(B10):B10306.
Weaver R L, Lobkis O I. Diffuse fields in open systems and the emergence of the Green's function[J]. Journal of the Acoustical Society of America, 2004, 117(5):2394.
