低信噪比浅水区OBS测线初至拾取研究
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摘要
浅水区OBS(Ocean Bottom Seismograph)测线往往具有信噪比较低,空间假频发育严重的问题,导致OBS测线初至拾取困难,进而影响反演速度模型的可靠性.本文通过直达波校正,正演模拟校正和射线互逆实现对浅水区OBS测线初至的准确拾取和质控.直达波校正消除主要的时钟漂移量.通过多道地震与OBS的联合处理,充分利用多道地震浅层速度模型较准确的特点,通过正演模拟构建OBS道集,弥补了实际采集的OBS道集浅层空间假频严重的问题,正演模拟法基本消除了剩余时钟漂移量,校正后的OBS道集符合层析成像的要求,同时也解决了近偏移距初至拾取的问题.利用射线互逆的方法,通过不同OBS道集组合不同偏移距组的对比验证,解决了中远偏移距初至拾取对比验证问题.三步法基本解决低信噪比浅水区OBS测线初至拾取的问题,为速度反演获得准确的模型奠定了基础.
The OBS(Ocean Bottom Seismograph)data in shallow water environment had always been disturbed by low S/N ratio and space alias. This problem made it hard to pick the first break, then affected the reliability of the inversed velocity model. This paper used direct wave correction, forward modeling correction and ray trace reciprocal to pick the first break of the OBS.These methods could make sure the accurate of the picks and also were useful for quality control. The direct wave correction could remove the main clock drift. Combining the multi-channel seismic and OBS data processing, we used the accurate shallow velocity model of the multi-channel seismic to construct the OBS gather by forward modeling to make up the space alias of the actual OBS gather. This method could remove the residual clock drift and solve the problem of the first break picking caused by the space alias for the near offset. The ray trace reciprocal method could solve the problem of the faint first break picking for large offset of the OBS gather by sorting the OBS gather to different groups with the same offset range. The three steps could solve the problem of the first break picking of OBS gather in shallow water environment with low S/N ratio and it laid the foundation to achieve the accurate velocity model by inversion.
The OBS(Ocean Bottom Seismograph)data in shallow water environment had always been disturbed by low S/N ratio and space alias. This problem made it hard to pick the first break, then affected the reliability of the inversed velocity model. This paper used direct wave correction, forward modeling correction and ray trace reciprocal to pick the first break of the OBS.These methods could make sure the accurate of the picks and also were useful for quality control. The direct wave correction could remove the main clock drift. Combining the multi-channel seismic and OBS data processing, we used the accurate shallow velocity model of the multi-channel seismic to construct the OBS gather by forward modeling to make up the space alias of the actual OBS gather. This method could remove the residual clock drift and solve the problem of the first break picking caused by the space alias for the near offset. The ray trace reciprocal method could solve the problem of the faint first break picking for large offset of the OBS gather by sorting the OBS gather to different groups with the same offset range. The three steps could solve the problem of the first break picking of OBS gather in shallow water environment with low S/N ratio and it laid the foundation to achieve the accurate velocity model by inversion.
引文
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Eakin D H, Mcintosh K D, Van Avendonk H J A, et al. 2014. Crustal-scale seismic profiles across the Manila subduction zone: The transition from intraoceanic subduction to incipient collision [J]. Journal of Geophysical Research: Solid Earthe, 119(1): 1-17.
Huang L and Liu C Y. 2014. Evolutionary characteristics of the sags to the east of Tan-Lu Fault Zone, Bohai Bay Basin(China): Implications for hydrocarbon exploration and regional tectonic evolution [J]. Journal of Asian Earth Sciences, 79: 275-287.
Huang W, Gao W, Ding G. 1996. Neogene volcanism and Holocene earthquakes in the Tanlu fault zone, eastern China [J]. Tectonophysics, 260(4): 259-270.
Liu B. 2016. Seismic imaging of subsurface beneath rough seafloor in the north slope of South China Sea: OBS travel time inversion [J]. Geophysical and Geochemical Exploration(in Chinese), 40(6): 1244-1249. http: //doi.org/10.11720/wtyht.2016.6.30.
Lü Z Y, Qiu X L, Ye C M, et al. 2017. Data processing and phase identification of onshore-offshore 3 D seismic exploration in Zhujiangkou area [J]. Journal of tropical oceanography(in Chinese), 36(3): 80-85.
Jiang W L, Wang X, Tian T, et al. 2014. Detailed crustal structure of the North China and its implication for seismicity [J]. Journal of Asian Earth Sciences, 81: 53- 64.
Pan J, Liu B H, Hua Q F, et al. 2012. Forward modeling based on OBS and first break recognition research [J]. Progress in Geophysics(in Chinese), 27(6): 2437-2443, doi: 10.6038/j.issn.1004-2903.2012.06.018.
Qi J F,Yang Q. 2010. Cenozoic structural deformation and dynamic processes of the Bohai Bay basin province, China [J]. Marine and Petroleum Geology, 27(4): 757-771.
Qiu X L, Zhao M H, Ao W, et al. 2011. OBS survey and crustal structure of the Southwest Sub-basin and Nansha Block, South China Sea [J]. Chinese J. Geophys.(in Chinese), 54(12): 3117-3128, doi: 10.3969/j.issn.0001-5733.2011.12.012.
Xia S H, Cao J H, Wan K Y, et al. 2016. Role of the Wide-angle OBS Seismic Exploration in the Research of Marine Sedimentary Basin [J]. Advances in Earth Science(in Chinese), 31(11): 1111-1124.
Zelt C A, Ellis R M. 1988. Practical and efficient ray tracing in two-dimensional media for rapid travel-time and amplitude forward modeling [J]. Can. J. Explor. Geophys, 24: 16-31.
Zelt C A, Sain K, Naumenko J V, et al. 2003. Assessment of crustal velocity models using seismic refraction and reflection tomography [J]. Geophysical Journal International, 153(3): 609- 626.
Zelt C A, Smith R B. 1992. Seismic traveltime inversion for 2-D crustal velocity structure [J]. Geophysical Journal International, 108(1): 16-34.
Zhou L H, Fu L X, Lou D. 2012. Structural anatomy and dynamics of evolution of the Qikou Sag, Bohai Bay Basin: Implications for the destruction of North China craton [J]. Journal of Asian Earth Sciences, 47: 94-106.
刘斌. 2016. 南海北部陆坡崎岖海底区地震成像: OBS旅行时反演[J]. 物探与化探, 40(6): 1244-1249. http: //doi.org/10.11720/wtyht.2016.6.30.
吕作勇, 丘学林, 叶春明, 等. 2017. 珠江口区域海陆联合三维地震构造探测的数据处理与震相识别[J]. 热带海洋学报, 36(3): 80-85.
潘军, 刘保华, 华清峰, 等. 2012. 基于OBS的正演模拟与初至识别研究[J]. 地球物理学进展, 27(6): 2437-2443, doi: 10.6038/j.issn.1004-2903.2012.06.018.
丘学林, 赵明辉, 敖威, 等. 2011. 南海西南次海盆与南沙地块的OBS探测和地壳结构[J]. 地球物理学报, 54(12): 3117-3128, doi: 10.3969/j.issn.0001-5733.2011.12.012.
夏少红, 曹敬贺, 万奎元, 等. 2016. OBS广角地震探测在海洋沉积盆地研究中的作用[J]. 地球科学进展, 31(11): 1111-1124, doi: 10.11867/j.issn.1001-8166.2016.11.1111.
Eakin D H, Mcintosh K D, Van Avendonk H J A, et al. 2014. Crustal-scale seismic profiles across the Manila subduction zone: The transition from intraoceanic subduction to incipient collision [J]. Journal of Geophysical Research: Solid Earthe, 119(1): 1-17.
Huang L and Liu C Y. 2014. Evolutionary characteristics of the sags to the east of Tan-Lu Fault Zone, Bohai Bay Basin(China): Implications for hydrocarbon exploration and regional tectonic evolution [J]. Journal of Asian Earth Sciences, 79: 275-287.
Huang W, Gao W, Ding G. 1996. Neogene volcanism and Holocene earthquakes in the Tanlu fault zone, eastern China [J]. Tectonophysics, 260(4): 259-270.
Liu B. 2016. Seismic imaging of subsurface beneath rough seafloor in the north slope of South China Sea: OBS travel time inversion [J]. Geophysical and Geochemical Exploration(in Chinese), 40(6): 1244-1249. http: //doi.org/10.11720/wtyht.2016.6.30.
Lü Z Y, Qiu X L, Ye C M, et al. 2017. Data processing and phase identification of onshore-offshore 3 D seismic exploration in Zhujiangkou area [J]. Journal of tropical oceanography(in Chinese), 36(3): 80-85.
Jiang W L, Wang X, Tian T, et al. 2014. Detailed crustal structure of the North China and its implication for seismicity [J]. Journal of Asian Earth Sciences, 81: 53- 64.
Pan J, Liu B H, Hua Q F, et al. 2012. Forward modeling based on OBS and first break recognition research [J]. Progress in Geophysics(in Chinese), 27(6): 2437-2443, doi: 10.6038/j.issn.1004-2903.2012.06.018.
Qi J F,Yang Q. 2010. Cenozoic structural deformation and dynamic processes of the Bohai Bay basin province, China [J]. Marine and Petroleum Geology, 27(4): 757-771.
Qiu X L, Zhao M H, Ao W, et al. 2011. OBS survey and crustal structure of the Southwest Sub-basin and Nansha Block, South China Sea [J]. Chinese J. Geophys.(in Chinese), 54(12): 3117-3128, doi: 10.3969/j.issn.0001-5733.2011.12.012.
Xia S H, Cao J H, Wan K Y, et al. 2016. Role of the Wide-angle OBS Seismic Exploration in the Research of Marine Sedimentary Basin [J]. Advances in Earth Science(in Chinese), 31(11): 1111-1124.
Zelt C A, Ellis R M. 1988. Practical and efficient ray tracing in two-dimensional media for rapid travel-time and amplitude forward modeling [J]. Can. J. Explor. Geophys, 24: 16-31.
Zelt C A, Sain K, Naumenko J V, et al. 2003. Assessment of crustal velocity models using seismic refraction and reflection tomography [J]. Geophysical Journal International, 153(3): 609- 626.
Zelt C A, Smith R B. 1992. Seismic traveltime inversion for 2-D crustal velocity structure [J]. Geophysical Journal International, 108(1): 16-34.
Zhou L H, Fu L X, Lou D. 2012. Structural anatomy and dynamics of evolution of the Qikou Sag, Bohai Bay Basin: Implications for the destruction of North China craton [J]. Journal of Asian Earth Sciences, 47: 94-106.
刘斌. 2016. 南海北部陆坡崎岖海底区地震成像: OBS旅行时反演[J]. 物探与化探, 40(6): 1244-1249. http: //doi.org/10.11720/wtyht.2016.6.30.
吕作勇, 丘学林, 叶春明, 等. 2017. 珠江口区域海陆联合三维地震构造探测的数据处理与震相识别[J]. 热带海洋学报, 36(3): 80-85.
潘军, 刘保华, 华清峰, 等. 2012. 基于OBS的正演模拟与初至识别研究[J]. 地球物理学进展, 27(6): 2437-2443, doi: 10.6038/j.issn.1004-2903.2012.06.018.
丘学林, 赵明辉, 敖威, 等. 2011. 南海西南次海盆与南沙地块的OBS探测和地壳结构[J]. 地球物理学报, 54(12): 3117-3128, doi: 10.3969/j.issn.0001-5733.2011.12.012.
夏少红, 曹敬贺, 万奎元, 等. 2016. OBS广角地震探测在海洋沉积盆地研究中的作用[J]. 地球科学进展, 31(11): 1111-1124, doi: 10.11867/j.issn.1001-8166.2016.11.1111.