Influence of Noise Source on Seismic Interferometry in Western Junggar Basin

摘要

Ambient noise cross-correlation is now widely used in seismology to obtain the surface-wave part of Green's functions.But it is difficult to retrieve body waves from noise correlations.The difficulty lies mainly in characteristics of seismic noise and different processing schemes in seismic noise cross-correlations,which are studied in this paper.We used a series of 3-day-period seismic data in the process of seismic noise cross-correlations.The survey area is located in northwest China,which is far away from the ocean.Spectrum analysis shows that the energetic part of the seismic noise is in the range of 1-10 IIz,during which surface waves and reflections were detected prominently.After a series ofpreprocessing,we obtained different results from different noise data.Furthermore,results from spectrum analysis and cross-correlations show that the variances of cross-correlations are probably caused by different noise sources,including urban seismic noise and traffic noise.We concluded that,(1) The seismic noise in the frequency band from 1 Hz to 6 Hz consist predominantly of surface waves,mainly originated from the urban seismic noise; (2) The cross-correlations towards the direction of noise source show higher signal-to-noise ratio (SNR)and better symmetry; and (3) The traffic noise originated from the provincial road S221,which crosses the survey line,is powerful and abundant.We detected surface waves in the 1-6 Hz band and reflections in the 6-9 Hz band.