江苏省区域地表背景噪声特性的分析
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摘要
利用Welch方法,计算了江苏省"十五"数字地震台站地表背景噪声在0.01～20Hz频带范围内的功率谱值,结果显示在周期10～16s、4～8s处分别存在两个明显的峰值。对比白天和夜晚时段台站三分向地表背景噪声的功率密度谱比值发现,地表台站三分向背景噪声在高频段(≥1Hz)变化最为显著,在微震峰值频段(0.125～1Hz)几乎所有台站之间的差异都不大,低频段(≤0.125Hz)大部分台站垂直向白天时段的噪声水平比夜晚的值低,水平向则相反;但井下观测系统全频段内的比值变化都很小。此外,在2～16Hz频率范围内,沿长江的苏南—上海地区的平均噪声水平高于苏中和苏北地区,比NLNM(低噪声模型)值高约45dB左右;在0.125～1Hz频率范围内,江苏中东部的噪声水平高于其他区域,推测这可能是与区域地质构造差异有关。
In this paper,we adopted the Welch's method to estimate background noise velocity power spectral density(PSD)of the seismic stations in Jiangsu province at the range from 0.01s to 20Hz.We found that there are two dominant peaks at the periods T≈10-16 s、T≈4-8 s respectively.And the day/night spectral ratios of surface seismic stations show that the strongest variation for three components is at the frequency range ≥1 Hz,the ratio variations at the 0.125-1 Hz are not distinguished,and the day noise level of the vertical component are lower than the night time noise at the range of low frequency range(≤0.125 Hz),the horizontal components are reverse.At the same time,there is little change for day/night spectral ratios of boreholes stations at all frequency sections.In additional,we also discussed seismic noise characteristic on the terrain difference of Jiangsu,the results show that the southern Jiangsu-Shanghai region has significantly higher noise level than mid-northern at the high frequency range(2-16 Hz),which is about 45 dB higher than the NLNM.At 0.125-1 Hz,the mid-eastern region has higher noise than other region,these are considered to be caused by geological difference.
In this paper,we adopted the Welch's method to estimate background noise velocity power spectral density(PSD)of the seismic stations in Jiangsu province at the range from 0.01s to 20Hz.We found that there are two dominant peaks at the periods T≈10-16 s、T≈4-8 s respectively.And the day/night spectral ratios of surface seismic stations show that the strongest variation for three components is at the frequency range ≥1 Hz,the ratio variations at the 0.125-1 Hz are not distinguished,and the day noise level of the vertical component are lower than the night time noise at the range of low frequency range(≤0.125 Hz),the horizontal components are reverse.At the same time,there is little change for day/night spectral ratios of boreholes stations at all frequency sections.In additional,we also discussed seismic noise characteristic on the terrain difference of Jiangsu,the results show that the southern Jiangsu-Shanghai region has significantly higher noise level than mid-northern at the high frequency range(2-16 Hz),which is about 45 dB higher than the NLNM.At 0.125-1 Hz,the mid-eastern region has higher noise than other region,these are considered to be caused by geological difference.
引文
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Hasselmann K.1963.A statistical analysis of the generation of microsisms[J].Rev Geophys,1:177-209.
Longuet-Higgens MS.1950.A theory of the origin of microseisms[R].Phil Trans Surv Tech Rept.243:1-35.
Peterson J.1993.Observations and modeling of background seismic noise[R].U.S.Geol.Surv.Tech.Rept:93-322,1-95.
Rodgers P W,Taylor S R,Nakanishi K K.1987.Systerm and site noisein the regional seismic test network from0.1to20Hz[J].BSSA,7(2):663-687.
Uhrhammer R A.2000.Background noise PSD analysis of USNSN broad-band data for1998[R].Berkeley Seismological Laboratory report.
Withers MM,Aster R C,Yong C J,et al.1996.High frequency analy-sis of seismic background noise as a function of wind speed and shal-low depth[J].BSSA,86(4):1507-1515.
Zurn W,Widmer R.1995.On noise reduction in vertical seismic recordsbelow2mHz using local barometric pressure[J].GRL,22:3537-3540.
万永革.2007.数字信号处理的MATLAB实现[M].北京:科学出版社.
徐嘉伟.1980.郯庐断裂带的平移运动及其地质意义[C]//国际交流地质学术论文集.北京:地质出版社.
杨晶琼,杨周胜.2005.云南地震数字遥测台网子台地动噪声分析[J].地震研究,28(1):86-89.
张文佑,李阴愧,张弛,等.1986.中国及邻区海陆构造[M].北京:科学出版社.
Beauduin P P,Lognonne J,Montagner P,et al.1996.The effects of at-mospheric pressure changes on seismic signals,or how to improvethe quality of a station[J].BSSA,86(5):1760-1799.
Bernard P.1990.Historical sketch of microseisms from past to future[J].Earth planet interiors,63(1):145-150.
Butler R,Hutt C R.1992,Seismic noise on Rarotonga surface versusdownhole[J].EOS,73:548-549.
Daniel E M,Raymond P B.2004.Ambient noise levels in the continentalUnited States[J].BSSA,94(4):1517-1527.
Eleonore S.2000.Genevieve roult and lucianna astiz,GEOSCOPE sta-tion noise levels[J].BSSA,90(3):690-701.
Given HK.1990.Variations in broadband seismic noise at IRIS/IDAsta-tions in the USSR with implications for event detection[J].BSSA,80(5):2072～2088.
Grawford W C,Webb S C,Hildebrand J A.1991.Seafloor complianceobserved by long period pressure and displacement measurement[J].J G R,96:16151-16160.
Gurrola HJ,Minster HGiven H,et al.1990.Analysis of high frequencyseismic noise in the western United States and eastern Kazakhstan[J].BSSA,80(3):951-970.
Hasselmann K.1963.A statistical analysis of the generation of microsisms[J].Rev Geophys,1:177-209.
Longuet-Higgens MS.1950.A theory of the origin of microseisms[R].Phil Trans Surv Tech Rept.243:1-35.
Peterson J.1993.Observations and modeling of background seismic noise[R].U.S.Geol.Surv.Tech.Rept:93-322,1-95.
Rodgers P W,Taylor S R,Nakanishi K K.1987.Systerm and site noisein the regional seismic test network from0.1to20Hz[J].BSSA,7(2):663-687.
Uhrhammer R A.2000.Background noise PSD analysis of USNSN broad-band data for1998[R].Berkeley Seismological Laboratory report.
Withers MM,Aster R C,Yong C J,et al.1996.High frequency analy-sis of seismic background noise as a function of wind speed and shal-low depth[J].BSSA,86(4):1507-1515.
Zurn W,Widmer R.1995.On noise reduction in vertical seismic recordsbelow2mHz using local barometric pressure[J].GRL,22:3537-3540.
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