由长时间连续记录不压制地震信号提取近似格林函数的可行性研究
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摘要
从地震背景噪声、地震波直达波或者地震波尾波的相关函数中提取近似格林函数(Estimated Green’sFunction)已经成为地震学研究的一个热点.由近似格林函数中提取面波频散曲线,进而研究地壳和上地幔结构,已经成为地震学研究地球内部结构的一种新方法,其尺度由最初的几十千米发展到全球尺度.从原理上,只要由充分漫射波场的数据计算得到的互相关函数都可以得到近似格林函数,但在地震背景噪声数据的实际处理过程中,需要通过时间域的归一化处理压制地震信号的影响,然后利用频率域归一化压制单色噪声源影响和提高信噪比.但是时间域归一化的常用方法均为非线性,影响进一步提取噪声互相关函数(NCF)中的有效信息.我们通过对比有无时间域归一化和频率域归一化对不同数据进行计算得到了相似的NCF,发现时间域归一化处理并非必需,在此基础上频率域归一化处理也可以省略,由此得到一个简化的处理流程,直接计算长时间的地震记录的互相关函数得到近似格林函数,并且最大限度保留了原始振幅信息,可以更有效地用于研究噪声源.
Recently,there are huge amount studies on extracting the Estimated Green's Function(EGF) from seismic ambient noise,direct wave and coda wave.The Rayleigh wave dispersion from EGF is applied to image crust and upper mantle seismic structure from local to global scales.Theoretically,the cross-correlation function of seismic records due to diffusive wave fields could provide valid EGF between two receivers.But previous preprocessing of ambient seismic noise includes temporal normalization to suppress the effect of earthquake signals(body wave,surface wave,coda wave etc.) and spectral whitening to account localized microseismic signal,spectral amplitude difference and so on.Such temporal and spectral normalizations are non-linear and abandon information about noise sources.We have calculated the cross-correlation functions of continuous records without procedure of suppressing earthquake signals and spectral whitening,and found that the EGF could be extracted from the long time range stacking of cross correlation of raw data.More absolute amplitude information of noise source is kept in such EGFs obtained with our new procedure,which is helpful to study noise sources.
Recently,there are huge amount studies on extracting the Estimated Green's Function(EGF) from seismic ambient noise,direct wave and coda wave.The Rayleigh wave dispersion from EGF is applied to image crust and upper mantle seismic structure from local to global scales.Theoretically,the cross-correlation function of seismic records due to diffusive wave fields could provide valid EGF between two receivers.But previous preprocessing of ambient seismic noise includes temporal normalization to suppress the effect of earthquake signals(body wave,surface wave,coda wave etc.) and spectral whitening to account localized microseismic signal,spectral amplitude difference and so on.Such temporal and spectral normalizations are non-linear and abandon information about noise sources.We have calculated the cross-correlation functions of continuous records without procedure of suppressing earthquake signals and spectral whitening,and found that the EGF could be extracted from the long time range stacking of cross correlation of raw data.More absolute amplitude information of noise source is kept in such EGFs obtained with our new procedure,which is helpful to study noise sources.
引文
[1]Claerbout,J F.Synthesis of a layered medium from its acoustictransmission response[J].Geophysics,1968,33:264-269.
[2]Duvall,T L,Jeffferies S M,Harvey J W,and Pomerantz MA.Time-distance helioseismology[J].Nature,1993,362:430-432.
[3]Campillo,M and Paul A.Long-range correlations in thediffuse seismic coda[J].Science,2003,299:547-549.
[4]Shapiro,N M and Campillo M.Emergence of broadbandRayleigh waves from correlations of the ambient seismic noise[J].Geophys.Res.Lett.,2004,31,L07614,doi:10.1029/2004GL019491.
[5]Roux,P,Sabra K G,Gerstoft P,Kuperman W A and FehlerM C.P-waves from cross-correlation of seismic noise[J].Geophys.Res.Lett.,2005,32,L19303,doi:10.1029/2005GL023803.
[6]Schuster,G T,Gu J,Sheng J and Rickett J.Interferometric/daylight seismic imaging[J].Geophys.J.Int.,2004,137(2):838-852.
[7]Shapiro,N M,Campillo M,Stehly L and Ritzwoller M.High-resolution surface-wave tomography from ambientseismic noise[J].Science,2005,307:1615-1618.
[8]Lin,F C,Moschetti M P,and Ritzwoller M H.Surface wavetomography of the western United States from ambient seismicnoise:Rayleigh and Love wave phase velocity maps[J].Geophys.J.Int.,2008,173:281-298.
[9]Nishida,K,Montagner J,Kawakatsu H.Global surfacewave tomography using seismic hum[J].Science,2009,326:112-112.
[10]Zhan Z,Ni S,Helmberger D V and Clayton R W.Retrievalof Moho-reflected shear wave arrivals from ambient seismicnoise[J].Geophys.J.Int.,2010,182:408-420.
[11]Wang W T,Ni S D,Wang B S,composition of high frequencyambient noise from cross-correlation:A case study using asmall aperture array[J].Eearthquake Science,2010,23:433-438.
[12]齐诚,陈棋福,陈颙.利用背景噪声进行地震成像的新方法[J].地球物理学进展,2007,22(3):771-777.QI C,CHEN Q-F,CHEN Y.A new method for seismicimaging from ambient seismic noise[J].Progress inGeophysics.(in Chinese),2007,22(3):771-777.
[13]房立华,吴建平,吕作勇.华北地区基于噪声的瑞利面波群速度层析成像[J].地球物理学报,2009,52(3):663-671.Fang L-H,Wu J-P,Lu Z-Y.Rayleigh wave group velocitytomography from ambient seismic noise in North China[J].Chinese J.Geophys.(in Chinese),2009,52(3):663-671.
[14]Yang,Y.,et al.Rayleigh wave phase velocity maps of Tibetand the surrounding regions from ambient seismic noisetomography[J].Geochem.Geophys.Geosyst.,2010,11,Q08010,doi:10.1029/2010GC003119.
[15]Yao H,van der Hilst R D and de Hoop M V.Surface-wavearray tomography in SE Tibet from ambient seismic noise andtwo-station analysis—I.Phase velocity maps[J].Geophys.J.Int.,2006,166:732-744.
[16]李昱,姚华建,刘启元等.川西地区台阵环境噪声瑞利波相速度层析成像[J].地球物理学报,2010,53(4):842-852.Li Y,Yao H-J,Liu Q-Y et al.Phase velocity arraytomography of Rayleigh waves in western Sichuan fromambient seismic noise[J].Chinese J.Geophys.(inChinese),2010,53(4):842-852.
[17]Li H,Su W,Wang C-Y and Huang Z.Ambient noiseRayleigh wave tomography in western Sichuan and easternTibet[J].Earth Planet.Sci.Lett.,2009,282:201-211.
[18]刘志坤,黄金莉.利用背景噪声互相关研究汶川地震震源区地震波波速变化[J].地球物理学报,2010,53(4):853-863.Liu Z-K and Huang J-L.Temporal changes of seismicvelocity around the Wenchuan earthquake fault zone fromambient seismic noise correlation[J].Chinese J.Geophys.(in Chinese),2010,53(4):853-863.
[19]Zheng,S,Sun X,Song X,Yang Y,and Ritzwoller M H.Surface wave tomography of China from ambient seismic noisecorrelation[J].Geochem.Geosphys.Geosyst.,2008,9,Q05020.
[20]Bensen,G D,Ritzwoller M H,Barmin M Pet al.Processingseismic ambient noise data to obtain reliable broad-bandsurface wave dispersion measurements[J].Geophys.J.Int.,2007,169:1239-1260.
[21]Snieder R.The theory of coda wave interferometry[J].Pureappl.Geophys.2006,163:453-473.
[22]Shapiro,N M,Campillo M,Margerin L,Singh S K,Kostoglodov V and Pacheco J.The energy partitioning andthe diffusive character of the seismic coda[J].Bull.Seismol.Soc.Am.,2000,90:655-665.
[23]Margerin,L,Campillo M,Shapiro N M and van Tiggelen B.Residence time of diffuse waves in the crust as aphysicalinterpretation of coda Q:Application to seismograms recordedin Mexico[J].Geophys.J.Int.,1999 138:343-352.
[24]Snieder,R.Extracting the Green’s function from the correlationof coda waves:A derivation based on stationary phase[J].Physical Review E,2004,69,046610-1–046610-8.
[25]Paul A,Campillo M,Margerin L,Larose E and Derode A.Empirical synthesis of time-asymmetrical Green functionsfrom the correlation of coda waves[J].J.Geophys.Res.,2005,110,B08302.
[26]Yao H,Campman X,de Hoop M V,van der Hilst R.Estimation of surface wave Green’s functions fromcorrelation of direct waves,coda waves,and ambient noise inSE Tibet[J].Phys.Earth Planet.In.,2009,doi:10.1016/j.pepi.2009.07.002.
[27]Hong,T-K and Menke W.Tomographic investigation of thewear along the San Jacinto fault,southern California[J].Phys.Earth Planet.Int.,2006,155:236-248.
[28]Curtis A,Nicolson H,Halliday D,Trampert J and Baptie B.Virtual seismometers in the subsurface of the Earth fromseismic interferometry[J].Nature Geoscience,2009,2:700-704.
[29]Tonegawa,T and Nishida K.Inter-source body wave propagationsderived from seismic interferometry[J].Geophys.J.Int.,2010,183(2):861-868.
[30]Longuet-Higgins,M S.A theory on the origin of microseism[J].Philos.Trans.R.Soc.London,Ser.A.,1950,243(857):1-35.
[31]Kedar,S and Webb F H.The ocean's seismic hum[J].Science,2005,307:682-683.
[32]Shapiro,N M,Ritzwoller M H and Bensen G D.Sourcelocation of the 26sec microseism from cross-correlation ofambient seismic noise[J].Geophys.Res.Lett.,2006,33,L18310,doi:10.1029/2006GL027010.
[33]Zeng X and Ni S.A persistent localized microseismic sourcenear the Kyushu Island,Japan[J].Geophys.Res.Lett.,2010,37,L24307,doi:10.1029/2010GL045774.
[34]Gu Y J,Dublanko C,Lerner-Lam A,Brzak K and M Steckler.Probing the source of ambient seismic noise near the coasts ofsouthern Italy[J].Geophys.Res.Lett.,2007,34,L22315,doi:10.1029/2007GL031967.
[35]Prieto G A,Lawrence J F,and Beroza G C.Anelastic Earthstructure from the coherency of the ambient seismic field[J].J.Geophys.Res.,2009,114,B07303,doi:10.1029/2008JB006067.
[36]Yang Y and Ritzwoller M H.Characteristics of ambient seismicnoise as a source for surface wave tomography[J].Geochem.Geosphys.Geosyst.,2008,9,Q02008.
[37]Stehly L,Campillo M and Shapiro N M.A study of theseismic noise from its long-range correlation properties[J].J.Geophys.Res.,2006,111,B10306.
[38]鲁来玉,何正勤,丁志峰,姚志祥.华北科学探测台阵背景噪声特征分析[J].地球物理学报.2009,52(10):2566-2572.LU,L-Y,He Z-Q,Ding Z-F and Yao Z-X.Investigation ofambient noise source in North China array[J].Chinese J.Geophys.(in Chinese),2010,52(10):2566-2572.
[2]Duvall,T L,Jeffferies S M,Harvey J W,and Pomerantz MA.Time-distance helioseismology[J].Nature,1993,362:430-432.
[3]Campillo,M and Paul A.Long-range correlations in thediffuse seismic coda[J].Science,2003,299:547-549.
[4]Shapiro,N M and Campillo M.Emergence of broadbandRayleigh waves from correlations of the ambient seismic noise[J].Geophys.Res.Lett.,2004,31,L07614,doi:10.1029/2004GL019491.
[5]Roux,P,Sabra K G,Gerstoft P,Kuperman W A and FehlerM C.P-waves from cross-correlation of seismic noise[J].Geophys.Res.Lett.,2005,32,L19303,doi:10.1029/2005GL023803.
[6]Schuster,G T,Gu J,Sheng J and Rickett J.Interferometric/daylight seismic imaging[J].Geophys.J.Int.,2004,137(2):838-852.
[7]Shapiro,N M,Campillo M,Stehly L and Ritzwoller M.High-resolution surface-wave tomography from ambientseismic noise[J].Science,2005,307:1615-1618.
[8]Lin,F C,Moschetti M P,and Ritzwoller M H.Surface wavetomography of the western United States from ambient seismicnoise:Rayleigh and Love wave phase velocity maps[J].Geophys.J.Int.,2008,173:281-298.
[9]Nishida,K,Montagner J,Kawakatsu H.Global surfacewave tomography using seismic hum[J].Science,2009,326:112-112.
[10]Zhan Z,Ni S,Helmberger D V and Clayton R W.Retrievalof Moho-reflected shear wave arrivals from ambient seismicnoise[J].Geophys.J.Int.,2010,182:408-420.
[11]Wang W T,Ni S D,Wang B S,composition of high frequencyambient noise from cross-correlation:A case study using asmall aperture array[J].Eearthquake Science,2010,23:433-438.
[12]齐诚,陈棋福,陈颙.利用背景噪声进行地震成像的新方法[J].地球物理学进展,2007,22(3):771-777.QI C,CHEN Q-F,CHEN Y.A new method for seismicimaging from ambient seismic noise[J].Progress inGeophysics.(in Chinese),2007,22(3):771-777.
[13]房立华,吴建平,吕作勇.华北地区基于噪声的瑞利面波群速度层析成像[J].地球物理学报,2009,52(3):663-671.Fang L-H,Wu J-P,Lu Z-Y.Rayleigh wave group velocitytomography from ambient seismic noise in North China[J].Chinese J.Geophys.(in Chinese),2009,52(3):663-671.
[14]Yang,Y.,et al.Rayleigh wave phase velocity maps of Tibetand the surrounding regions from ambient seismic noisetomography[J].Geochem.Geophys.Geosyst.,2010,11,Q08010,doi:10.1029/2010GC003119.
[15]Yao H,van der Hilst R D and de Hoop M V.Surface-wavearray tomography in SE Tibet from ambient seismic noise andtwo-station analysis—I.Phase velocity maps[J].Geophys.J.Int.,2006,166:732-744.
[16]李昱,姚华建,刘启元等.川西地区台阵环境噪声瑞利波相速度层析成像[J].地球物理学报,2010,53(4):842-852.Li Y,Yao H-J,Liu Q-Y et al.Phase velocity arraytomography of Rayleigh waves in western Sichuan fromambient seismic noise[J].Chinese J.Geophys.(inChinese),2010,53(4):842-852.
[17]Li H,Su W,Wang C-Y and Huang Z.Ambient noiseRayleigh wave tomography in western Sichuan and easternTibet[J].Earth Planet.Sci.Lett.,2009,282:201-211.
[18]刘志坤,黄金莉.利用背景噪声互相关研究汶川地震震源区地震波波速变化[J].地球物理学报,2010,53(4):853-863.Liu Z-K and Huang J-L.Temporal changes of seismicvelocity around the Wenchuan earthquake fault zone fromambient seismic noise correlation[J].Chinese J.Geophys.(in Chinese),2010,53(4):853-863.
[19]Zheng,S,Sun X,Song X,Yang Y,and Ritzwoller M H.Surface wave tomography of China from ambient seismic noisecorrelation[J].Geochem.Geosphys.Geosyst.,2008,9,Q05020.
[20]Bensen,G D,Ritzwoller M H,Barmin M Pet al.Processingseismic ambient noise data to obtain reliable broad-bandsurface wave dispersion measurements[J].Geophys.J.Int.,2007,169:1239-1260.
[21]Snieder R.The theory of coda wave interferometry[J].Pureappl.Geophys.2006,163:453-473.
[22]Shapiro,N M,Campillo M,Margerin L,Singh S K,Kostoglodov V and Pacheco J.The energy partitioning andthe diffusive character of the seismic coda[J].Bull.Seismol.Soc.Am.,2000,90:655-665.
[23]Margerin,L,Campillo M,Shapiro N M and van Tiggelen B.Residence time of diffuse waves in the crust as aphysicalinterpretation of coda Q:Application to seismograms recordedin Mexico[J].Geophys.J.Int.,1999 138:343-352.
[24]Snieder,R.Extracting the Green’s function from the correlationof coda waves:A derivation based on stationary phase[J].Physical Review E,2004,69,046610-1–046610-8.
[25]Paul A,Campillo M,Margerin L,Larose E and Derode A.Empirical synthesis of time-asymmetrical Green functionsfrom the correlation of coda waves[J].J.Geophys.Res.,2005,110,B08302.
[26]Yao H,Campman X,de Hoop M V,van der Hilst R.Estimation of surface wave Green’s functions fromcorrelation of direct waves,coda waves,and ambient noise inSE Tibet[J].Phys.Earth Planet.In.,2009,doi:10.1016/j.pepi.2009.07.002.
[27]Hong,T-K and Menke W.Tomographic investigation of thewear along the San Jacinto fault,southern California[J].Phys.Earth Planet.Int.,2006,155:236-248.
[28]Curtis A,Nicolson H,Halliday D,Trampert J and Baptie B.Virtual seismometers in the subsurface of the Earth fromseismic interferometry[J].Nature Geoscience,2009,2:700-704.
[29]Tonegawa,T and Nishida K.Inter-source body wave propagationsderived from seismic interferometry[J].Geophys.J.Int.,2010,183(2):861-868.
[30]Longuet-Higgins,M S.A theory on the origin of microseism[J].Philos.Trans.R.Soc.London,Ser.A.,1950,243(857):1-35.
[31]Kedar,S and Webb F H.The ocean's seismic hum[J].Science,2005,307:682-683.
[32]Shapiro,N M,Ritzwoller M H and Bensen G D.Sourcelocation of the 26sec microseism from cross-correlation ofambient seismic noise[J].Geophys.Res.Lett.,2006,33,L18310,doi:10.1029/2006GL027010.
[33]Zeng X and Ni S.A persistent localized microseismic sourcenear the Kyushu Island,Japan[J].Geophys.Res.Lett.,2010,37,L24307,doi:10.1029/2010GL045774.
[34]Gu Y J,Dublanko C,Lerner-Lam A,Brzak K and M Steckler.Probing the source of ambient seismic noise near the coasts ofsouthern Italy[J].Geophys.Res.Lett.,2007,34,L22315,doi:10.1029/2007GL031967.
[35]Prieto G A,Lawrence J F,and Beroza G C.Anelastic Earthstructure from the coherency of the ambient seismic field[J].J.Geophys.Res.,2009,114,B07303,doi:10.1029/2008JB006067.
[36]Yang Y and Ritzwoller M H.Characteristics of ambient seismicnoise as a source for surface wave tomography[J].Geochem.Geosphys.Geosyst.,2008,9,Q02008.
[37]Stehly L,Campillo M and Shapiro N M.A study of theseismic noise from its long-range correlation properties[J].J.Geophys.Res.,2006,111,B10306.
[38]鲁来玉,何正勤,丁志峰,姚志祥.华北科学探测台阵背景噪声特征分析[J].地球物理学报.2009,52(10):2566-2572.LU,L-Y,He Z-Q,Ding Z-F and Yao Z-X.Investigation ofambient noise source in North China array[J].Chinese J.Geophys.(in Chinese),2010,52(10):2566-2572.
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