中文摘要：

利用华北科学探测台阵180多个宽频带台站2007年的连续记录，得到了台站之间噪声互相关函数.通过对三个分量记录的相关运算，获得了Rayleigh波和Love波的经验格林函数，分析了其信噪比随周期的变化和高信噪比台站对的方位分布.利用经验格林函数的非对称性和聚束方法，研究了华北科学探测台阵地震噪声的方位分布，及其季节变化特征.尽管噪声源的分布随季节有轻微变化，但全年的分析结果表明，10～32 s周期内华北台阵的地震噪声源在各个方向上的分布近于均匀，这为利用噪声成像提供了理论前提.

英文摘要：

Noise Cross-Correlation Function （NCF） is obtained by processing one-year ambient noise observed at over 180 broad-band stations from North China Array. All available three-component time series are used to extract the Rayleigh and Love waves. The Signal-to-Noise Ratio （SNR） at different periods and the azimuth distribution of the inter-station pairs with high SNR are discussed. The azimuth distributions of the ambient noise source are investigated by analyzing the beamforming output. Although seasonal variations are observed from the beamforming output, the source distribution at 10-32 s is almost uniformly distributed in all directions, which allows us to perform the following detailed tomography safely.