基于相邻虚拟道叠加的超虚折射干涉法及其在广角OBS折射波增强中的应用
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摘要
广角地震的远偏移距折射初至含有地下深层的信息,提高远偏移距折射波信噪比能够有效提高初至拾取精度,对于深部结构的层析速度建模十分有利.超虚折射干涉法基于干涉原理对远道折射波进行增强,它在炮点和检波点都非常密集的情况下效果较好.然而,在应用于台站间距较大且环境噪声较强的广角海底地震仪(OBS)观测时,该方法对折射波的增强能力不足,而且容易产生虚假波形,造成增强后的折射波信噪比仍然较低.针对这种情况,本文提出基于相邻虚拟道叠加的超虚折射干涉法,通过叠加相邻虚拟道来提高远道与近道互相关的准确度,以达到稳定增强远道折射波信噪比的目的.理论实验和实际资料测试均显示,基于相邻虚拟道叠加的超虚折射干涉法在台站间距较大和信噪比较低的情况下能够准确构建虚拟道,且增强后的波形同相轴连续程度和信噪比均较高,有利于拾取高精度的折射初至到时.本文方法也可用于增强陆上炮间距较大的广角地震数据折射波.
The first-arrival of far-offset refraction waves of wide-angle seismic data carries the information of structure in the deep subsurface.Enhancing the signal-to-noise ratio(SNR)of these waves can effectively improve the accuracy of first-arrival picking up,and would be very helpful for the tomographic velocity modeling of deep structures.The Supervirtual RefractionInterferometry(SRI)method can enhance refraction waves based on the principle of interference.It works well when the shots and receivers are densely distributed.However,when the SRI method is applied to the wide-angle Ocean Bottom Seismometer(OBS)observation with large station space and under high environmental noise,it cannot sufficiently enhance the refraction waves and could create artifacts in resulted waveforms,leading to low SNR of refraction waves.To cope with this problem,we propose a supervirtual refraction interferometry based on the stacking of neighboring virtual-traces(SRI-SNV).By stacking neighboring virtual-traces,our method can stably increase the accuracy of cross-correlation between the far-and near-offset traces,and achieve the high SNR of refraction waves.The synthetic tests and field-data applications both indicate that SRI-SNV can accurately construct virtual-traces under the situation of large station spacing and low SNR,and the resulted refraction waveforms have better continuity and higher SNR than the SRI method.Using the waveforms enhanced by the SRISNV,the first-arrival picking up can achieve higher accuracy than using the SRI method.The SRI-SNV method can also be used to enhance the seismic refraction waves of the wide-angle seismic data on land,which has large shot interval.
The first-arrival of far-offset refraction waves of wide-angle seismic data carries the information of structure in the deep subsurface.Enhancing the signal-to-noise ratio(SNR)of these waves can effectively improve the accuracy of first-arrival picking up,and would be very helpful for the tomographic velocity modeling of deep structures.The Supervirtual RefractionInterferometry(SRI)method can enhance refraction waves based on the principle of interference.It works well when the shots and receivers are densely distributed.However,when the SRI method is applied to the wide-angle Ocean Bottom Seismometer(OBS)observation with large station space and under high environmental noise,it cannot sufficiently enhance the refraction waves and could create artifacts in resulted waveforms,leading to low SNR of refraction waves.To cope with this problem,we propose a supervirtual refraction interferometry based on the stacking of neighboring virtual-traces(SRI-SNV).By stacking neighboring virtual-traces,our method can stably increase the accuracy of cross-correlation between the far-and near-offset traces,and achieve the high SNR of refraction waves.The synthetic tests and field-data applications both indicate that SRI-SNV can accurately construct virtual-traces under the situation of large station spacing and low SNR,and the resulted refraction waveforms have better continuity and higher SNR than the SRI method.Using the waveforms enhanced by the SRISNV,the first-arrival picking up can achieve higher accuracy than using the SRI method.The SRI-SNV method can also be used to enhance the seismic refraction waves of the wide-angle seismic data on land,which has large shot interval.
引文
Al-Hagan O,Hanafy S M,Schuster G.2014.Iterative supervirtual refraction interferometry.Geophysics,79(3):Q21-Q30,doi:10.1190/geo2013-0210.1.
Alshuhail A,Aldawood A,Hanafy S.2012.Application of supervirtual seismic refraction interferometry to enhance first arrivals:Acase study from Saudi Arabia.The Leading Edge,31(1):34-39,doi:10.1190/1.3679326.
Al-Shuhail A A.2015.Improving automatic first-arrival picking by supervirtual interferometry:examples from Saudi Arabia.Arab.J.Geosci.,8(10):8731-8740,doi:10.1007/s12517-015-1804-9.
An S P,Liang X H,Peng G X,et al.2015.Recognization and identification of first-arrival refractions in low SNR prestack seismic data.OGP(in Chinese),50(3):451-459,468.
An S P,Hu T Y,Liu Y M,et al.2017a.Automatic first-arrival picking based on extended super-virtual interferometry with quality control procedure.Explor.Geophys.,48(2):124-130.
An S P,Hu T Y,Peng G X.2017b.Three-dimensional cumulantbased coherent integration method to enhance first-break seismic signals.IEEE Transactions on Geoscience and Remote Sensing,55(4):2089-2096.
Bharadwaj P,Schuster G T,Mallinson I.2011.Super-virtual refraction interferometry:Theory.∥81st SEG Annual Meeting,Expanded Abstracts.SEG,3809-3813.
Bharadwaj P,Schuster G,Mallinson I,et al.2012.Theory of supervirtual refraction interferometry.Geophys.J.Int.,188(1):263-273,doi:10.1111/j.1365-246x.2011.05253.x.
Bharadwaj P,Wang X,Schuster G,et al.2013.Increasing the number and signal-to-noise ratio of OBS traces with supervirtual refraction interferometry and free-surface multiples.Geophys.J.Int.,192(3):1070-1084,doi:10.1093/gji/ggs087.
Bharadwaj P,Nissen-Meyer T,Schuster G,et al.2014.Enhancing core-diffracted arrivals by supervirtual interferometry.Geophys.J.Int.,196(2):1177-1188,doi:10.1093/gji/ggt452.
Dong S Q,Sheng J M,Schuster J T.2006.Theory and practice of refraction interferometry.∥76th SEG Annual Meeting,Expanded Abstracts.New Orleans,Louisiana:SEG,3021-3025.
Funck T,Andersen M S,Neish J K,et al.2008.A refraction seismic transect from the Faroe Islands to the Hatton-Rockall Basin.J.Geophys.Res.,113(B12):178-196,B12405,doi:10.1029/2008jb005675.
Hanafy S M,Al-Hagan O,Al-Tawash F.2011.Super-virtual refraction interferometry:Field data example over a colluvial wedge.∥81st SEG Annual Meeting,Expanded Abstracts.San Antonio,Texas:SEG,3814-3818.
Lin F S,Zou Z H.2016.Automatic seismic first-arrival picking method based on the combination of STA/LTA and multichannel cross correlation.∥12st National Safety Geophysical Series-Geophysics and Information Perception(in Chinese).Beijing:Chinese Geophysical Society,74-80.
Liu J,Wu S Y,Shi J.2015.Application of pre-stack noise suppression technique in the South Yellow Sea.Marine Geology and Quaternary Geology(in Chinese),35(6):165-173,doi:10.16562/j.cnki.0256-1492.2015.06.017.
Liu L H,Hao T Y,LüC C,et al.2015.Crustal structure of Bohai Sea and adjacent area(North China)from two onshore-offshore wide-angle seismic survey lines.J.Asian Earth Sci.,98:457-469,doi:10.1016/j.jseaes.2014.11.034.
Lu K,Altheyab A,Schuster G T.2014.3Dsuper-virtual refraction interferometry.∥84th SEG Annual Meeting,Expanded Abstracts.SEG,4203-4207.
Lv X M,An S P,Hu T Y,et al.2018.Similarity-weighted supervirtual interferometry to enhance first breaks.Acta Scientiarum Naturalium Universitatis Pekinensis(in Chinese),54(1):87-93,doi:10.13209/j.0479-8023.2017.071.
Mallinson I,Bharadwaj P,Schuster G,et al.2011.Enhanced refractor imaging by supervirtual interferometry.The Leading Edge,30(5):546-550,doi:10.1190/1.3589113.
Ma R,Zou Z H.2017.Composite absorption boundary conditions of pseudo spectral elastic wave simulation.2017 Geophysical Technology Symposium of Chinese Petroleum Society(in Chinese).Tianjin,1052-1055.
Mooney W D,Weaver C S.1989.Regional crustal structure and tectonics of the Pacific Coastal States;California,Oregon,and Washington.Memoir of the Geological Society of America,172(1):129-161,doi:10.1130/MEM172-p129.
Moser T J.1991.Shortest path calculation of seismic rays.Geophysics,56(1):59-67.
Operto S,Charvis P.1996.Deep structure of the southern Kerguelen Plateau(southern Indian Ocean)from ocean bottom seismometer wide-angle seismic data.J.Geophys.Res.,101(B11):25077-25103,doi:10.1029/96JB01758.
Qiao B P,Guo P,Wang P,et al.2014.Effectively picking weak seismic signal near the surface based on reverse virtual refraction interferometry.Chinese J.Geophys.(in Chinese),57(6):1900-1909,doi:10.6038/cjg20140621.
Ruan A G,Niu X W,Qiu X L,et al.2011.A wide angle Ocean Bottom Seismometer profile across Liyue Bank,the southern margin of South China Sea.Chinese J.Geophys.(in Chinese),54(12):3139-3149,doi:10.3969/j.issn.0001-5733.2011.12.014.
Wang S J,Wang F Y,Zhang J S,et al.2014.The P-wave velocity structure of the lithosphere of the North China CratonResults from the Wendeng-Alxa Left Banner deep seismic sounding profile.Sci.China:Earth Sci.,57(9):2053-2063,doi:10.1007/s11430-014-4903-7.
Wei X D,Ruan A G,Zhao M H,et al.2011.A wide-angle OBSprofile across Dongsha Uplift and Chaoshan Depression in the mid-northern South China Sea.Chinese J.Geophys.(in Chinese),54(12):3325-3335,doi:10.3969/j.issn.0001-5733.2011.12.030.
Wu Z L,Li J B,Ruan A G,et al.2011.Crustal structure of the northwestern sub-basin,South China Sea:results from a wideangle seismic experiment.Sci.China:Earth Sci.,55(1):159-172.
Yan P,Zhou D,Liu Z S.2001.A crustal structure profile across the northern continental margin of the South China Sea.Tectonophysics,338(1):1-21,doi:10.1016/s0040-1951(01)00062-2.
Zou Z H,Liu K,Zhao W N,et al.2016.Upper crustal structure beneath the northern South Yellow Sea revealed by wide-angle seismic tomography and joint interpretation of geophysical data.Geol.J.,51(S1):108-122,doi:10.1002/gj.2847.
安圣培,梁向豪,彭更新等.2015.低信噪比地震数据折射初至的判定与识别.石油地球物理勘探,50(3):451-459,468.
林凡生,邹志辉.2016.基于STA/LTA与多道互相关结合的地震波初至自动拾取方法.∥国家安全地球物理丛书(十二)---地球物理与信息感知.北京:中国地球物理学会,74-80.
刘俊,吴淑玉,施剑.2015.南黄海地震资料叠前去噪技术应用.海洋地质与第四纪地质,35(6):165-173,doi:10.16562/j.cnki.0256-1492.2015.06.017.
吕雪梅,安圣培,胡天跃等.2018.相似度加权的超虚干涉法加强初至波信号.北京大学学报(自然科学版),54(1):87-93,doi:10.13209/j.0479-8023.2017.071.
马锐,邹志辉.2017.伪谱法弹性波模拟的复合吸收边界条件.∥中国石油学会2017年物探技术研讨会论文集.天津,1052-1055.
乔宝平,郭平,王璞等.2014.基于逆虚折射干涉法有效提取近地表弱地震信号.地球物理学报,57(6):1900-1909,doi:10.6038/cjg20140621.
阮爱国,牛雄伟,丘学林等.2011.穿越南沙礼乐滩的海底地震仪广角地震试验.地球物理学报,54(12):3139-3149,doi:10.3969/j.issn.0001-5733.2011.12.014.
王帅军,王夫运,张建狮等.2014.华北克拉通岩石圈二维P波速度结构特征---文登-阿拉善左旗深地震测深剖面结果.中国科学:地球科学,44(12):2697-2708.
卫小冬,阮爱国,赵明辉等.2011.穿越东沙隆起和潮汕坳陷的OBS广角地震剖面.地球物理学报,54(12):3325-3335,doi:10.3969/j.issn.0001-5733.2011.12.030.
吴振利,李家彪,阮爱国等.2011.南海西北次海盆地壳结构:海底广角地震实验结果.中国科学:地球科学,41(10):1463-1476.
Alshuhail A,Aldawood A,Hanafy S.2012.Application of supervirtual seismic refraction interferometry to enhance first arrivals:Acase study from Saudi Arabia.The Leading Edge,31(1):34-39,doi:10.1190/1.3679326.
Al-Shuhail A A.2015.Improving automatic first-arrival picking by supervirtual interferometry:examples from Saudi Arabia.Arab.J.Geosci.,8(10):8731-8740,doi:10.1007/s12517-015-1804-9.
An S P,Liang X H,Peng G X,et al.2015.Recognization and identification of first-arrival refractions in low SNR prestack seismic data.OGP(in Chinese),50(3):451-459,468.
An S P,Hu T Y,Liu Y M,et al.2017a.Automatic first-arrival picking based on extended super-virtual interferometry with quality control procedure.Explor.Geophys.,48(2):124-130.
An S P,Hu T Y,Peng G X.2017b.Three-dimensional cumulantbased coherent integration method to enhance first-break seismic signals.IEEE Transactions on Geoscience and Remote Sensing,55(4):2089-2096.
Bharadwaj P,Schuster G T,Mallinson I.2011.Super-virtual refraction interferometry:Theory.∥81st SEG Annual Meeting,Expanded Abstracts.SEG,3809-3813.
Bharadwaj P,Schuster G,Mallinson I,et al.2012.Theory of supervirtual refraction interferometry.Geophys.J.Int.,188(1):263-273,doi:10.1111/j.1365-246x.2011.05253.x.
Bharadwaj P,Wang X,Schuster G,et al.2013.Increasing the number and signal-to-noise ratio of OBS traces with supervirtual refraction interferometry and free-surface multiples.Geophys.J.Int.,192(3):1070-1084,doi:10.1093/gji/ggs087.
Bharadwaj P,Nissen-Meyer T,Schuster G,et al.2014.Enhancing core-diffracted arrivals by supervirtual interferometry.Geophys.J.Int.,196(2):1177-1188,doi:10.1093/gji/ggt452.
Dong S Q,Sheng J M,Schuster J T.2006.Theory and practice of refraction interferometry.∥76th SEG Annual Meeting,Expanded Abstracts.New Orleans,Louisiana:SEG,3021-3025.
Funck T,Andersen M S,Neish J K,et al.2008.A refraction seismic transect from the Faroe Islands to the Hatton-Rockall Basin.J.Geophys.Res.,113(B12):178-196,B12405,doi:10.1029/2008jb005675.
Hanafy S M,Al-Hagan O,Al-Tawash F.2011.Super-virtual refraction interferometry:Field data example over a colluvial wedge.∥81st SEG Annual Meeting,Expanded Abstracts.San Antonio,Texas:SEG,3814-3818.
Lin F S,Zou Z H.2016.Automatic seismic first-arrival picking method based on the combination of STA/LTA and multichannel cross correlation.∥12st National Safety Geophysical Series-Geophysics and Information Perception(in Chinese).Beijing:Chinese Geophysical Society,74-80.
Liu J,Wu S Y,Shi J.2015.Application of pre-stack noise suppression technique in the South Yellow Sea.Marine Geology and Quaternary Geology(in Chinese),35(6):165-173,doi:10.16562/j.cnki.0256-1492.2015.06.017.
Liu L H,Hao T Y,LüC C,et al.2015.Crustal structure of Bohai Sea and adjacent area(North China)from two onshore-offshore wide-angle seismic survey lines.J.Asian Earth Sci.,98:457-469,doi:10.1016/j.jseaes.2014.11.034.
Lu K,Altheyab A,Schuster G T.2014.3Dsuper-virtual refraction interferometry.∥84th SEG Annual Meeting,Expanded Abstracts.SEG,4203-4207.
Lv X M,An S P,Hu T Y,et al.2018.Similarity-weighted supervirtual interferometry to enhance first breaks.Acta Scientiarum Naturalium Universitatis Pekinensis(in Chinese),54(1):87-93,doi:10.13209/j.0479-8023.2017.071.
Mallinson I,Bharadwaj P,Schuster G,et al.2011.Enhanced refractor imaging by supervirtual interferometry.The Leading Edge,30(5):546-550,doi:10.1190/1.3589113.
Ma R,Zou Z H.2017.Composite absorption boundary conditions of pseudo spectral elastic wave simulation.2017 Geophysical Technology Symposium of Chinese Petroleum Society(in Chinese).Tianjin,1052-1055.
Mooney W D,Weaver C S.1989.Regional crustal structure and tectonics of the Pacific Coastal States;California,Oregon,and Washington.Memoir of the Geological Society of America,172(1):129-161,doi:10.1130/MEM172-p129.
Moser T J.1991.Shortest path calculation of seismic rays.Geophysics,56(1):59-67.
Operto S,Charvis P.1996.Deep structure of the southern Kerguelen Plateau(southern Indian Ocean)from ocean bottom seismometer wide-angle seismic data.J.Geophys.Res.,101(B11):25077-25103,doi:10.1029/96JB01758.
Qiao B P,Guo P,Wang P,et al.2014.Effectively picking weak seismic signal near the surface based on reverse virtual refraction interferometry.Chinese J.Geophys.(in Chinese),57(6):1900-1909,doi:10.6038/cjg20140621.
Ruan A G,Niu X W,Qiu X L,et al.2011.A wide angle Ocean Bottom Seismometer profile across Liyue Bank,the southern margin of South China Sea.Chinese J.Geophys.(in Chinese),54(12):3139-3149,doi:10.3969/j.issn.0001-5733.2011.12.014.
Wang S J,Wang F Y,Zhang J S,et al.2014.The P-wave velocity structure of the lithosphere of the North China CratonResults from the Wendeng-Alxa Left Banner deep seismic sounding profile.Sci.China:Earth Sci.,57(9):2053-2063,doi:10.1007/s11430-014-4903-7.
Wei X D,Ruan A G,Zhao M H,et al.2011.A wide-angle OBSprofile across Dongsha Uplift and Chaoshan Depression in the mid-northern South China Sea.Chinese J.Geophys.(in Chinese),54(12):3325-3335,doi:10.3969/j.issn.0001-5733.2011.12.030.
Wu Z L,Li J B,Ruan A G,et al.2011.Crustal structure of the northwestern sub-basin,South China Sea:results from a wideangle seismic experiment.Sci.China:Earth Sci.,55(1):159-172.
Yan P,Zhou D,Liu Z S.2001.A crustal structure profile across the northern continental margin of the South China Sea.Tectonophysics,338(1):1-21,doi:10.1016/s0040-1951(01)00062-2.
Zou Z H,Liu K,Zhao W N,et al.2016.Upper crustal structure beneath the northern South Yellow Sea revealed by wide-angle seismic tomography and joint interpretation of geophysical data.Geol.J.,51(S1):108-122,doi:10.1002/gj.2847.
安圣培,梁向豪,彭更新等.2015.低信噪比地震数据折射初至的判定与识别.石油地球物理勘探,50(3):451-459,468.
林凡生,邹志辉.2016.基于STA/LTA与多道互相关结合的地震波初至自动拾取方法.∥国家安全地球物理丛书(十二)---地球物理与信息感知.北京:中国地球物理学会,74-80.
刘俊,吴淑玉,施剑.2015.南黄海地震资料叠前去噪技术应用.海洋地质与第四纪地质,35(6):165-173,doi:10.16562/j.cnki.0256-1492.2015.06.017.
吕雪梅,安圣培,胡天跃等.2018.相似度加权的超虚干涉法加强初至波信号.北京大学学报(自然科学版),54(1):87-93,doi:10.13209/j.0479-8023.2017.071.
马锐,邹志辉.2017.伪谱法弹性波模拟的复合吸收边界条件.∥中国石油学会2017年物探技术研讨会论文集.天津,1052-1055.
乔宝平,郭平,王璞等.2014.基于逆虚折射干涉法有效提取近地表弱地震信号.地球物理学报,57(6):1900-1909,doi:10.6038/cjg20140621.
阮爱国,牛雄伟,丘学林等.2011.穿越南沙礼乐滩的海底地震仪广角地震试验.地球物理学报,54(12):3139-3149,doi:10.3969/j.issn.0001-5733.2011.12.014.
王帅军,王夫运,张建狮等.2014.华北克拉通岩石圈二维P波速度结构特征---文登-阿拉善左旗深地震测深剖面结果.中国科学:地球科学,44(12):2697-2708.
卫小冬,阮爱国,赵明辉等.2011.穿越东沙隆起和潮汕坳陷的OBS广角地震剖面.地球物理学报,54(12):3325-3335,doi:10.3969/j.issn.0001-5733.2011.12.030.
吴振利,李家彪,阮爱国等.2011.南海西北次海盆地壳结构:海底广角地震实验结果.中国科学:地球科学,41(10):1463-1476.