新疆和田台阵PSD与PDF分析

Ambient noise analysis by the technology of PSD and PDF in Hotan Seismic Array

和田台阵是我国第一个自主建成并运行至今的小孔径台阵,承担着监测印巴地区核试验以及我国西部地震活动的重要使命.台阵波形数据中充斥着背景噪声,直接影响着数据质量.为了评估台阵噪声水平,本文利用Welch平均周期法对9个子台记录的数十万条噪声样本进行功率谱估计,对出现的谱异常进行了总结归纳,通过绘制概率密度函数图以及单频曲线来研究背景噪声变化范围和规律,最后针对台阵降噪提出了建设性意见.研究结果表明,中心台长周期噪声功率谱密度随季节变化显著,具有周期性;受温度和气压影响,水平分量长周期噪声变化幅度较大,局部频段超出新高噪声模型,建议改善仪器安装条件,或者利用数学方法进行校正.所有子台短周期噪声变化规律与长周期相反,受到采石场影响,谱密度曲线在4~8Hz之间出现形态规则的高频尖刺,A1、B3、B4子台最为明显,可以通过窄带滤波或者聚束予以压制.本文取得的研究成果为台阵运维提供重要依据,除此之外,总结出的不同地震频谱特征也为地震解释工作提供重要参考.

Hotan Array is the first small-aperture array in China that has been independently built and operated till now. It is responsible for monitoring the nuclear test in India and Pakistan and the earthquake activity in western China. The waveform data of the array is full of ambient noise,which directly affects the data quality. In order to evaluate the noise level of the array,the Welch average period method is utilized to estimate the power spectrum of hundreds of thousands of noise samples recorded by 9 sub-stations in this paper,so as to summarize the spectrum anomalies. On this basis,the probability density function graph and the single-frequency curve are plotted to study the variation range and law of ambient noise,so as to finally put forward constructive opinions on the noise reduction of the array. The research results show that the long-period noise power spectral density of the central station varies significantly with the seasons,characterized by periodicity. Due to the influence of temperature and pressure,the horizontal component long-period noise changes greatly,and the local frequency band exceeds the NHNM in winter. It is recommended to improve the instrument installation conditions,or use mathematical methods to correct. The short-period noise variation of all sub-stations is opposite to that of the long-period. Affected by the quarry,the spectral density curve shows a regular high-frequency tip between 4~8 Hz. The A1,B3 and B4 sub-stations are the most obvious,able to pass narrow-band filtering or bunching to suppress. The research results obtained in this paper provide an important basis for the operation and maintenance of array. In addition,the different seismic spectrum features summarized are important references for seismic interpretation.