初至波层析成像的反演参数选取:以南海中央次海盆三维地震探测数据为例
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摘要
FAST(first arrival seismic tomography)软件是获取复杂地区三维深部结构的最常用工具之一,而反演参数选取是快速有效地获得真实合理的地震结构的关键环节。以南海中央次海盆三维地震探测数据为基础,采用先固定其中一个参数、选取另外一个参数、再综合选取的控制变量法,详细地介绍了FAST反演参数组合的选取过程。选取结果表明,反演参数组合(阻尼因子λ=2,平滑度权重因子sz=1,反演次数I=4)为南海中央次海盆三维地震结构的最佳反演参数,由此获得的最佳初步速度模型表明中央次海盆具有典型慢速扩张的洋壳结构。此项反演参数选取工作不仅为珍贝-黄岩海山链精细三维地震结构的正式模拟奠定了基础,同时为FAST软件在其他地区的应用提供了丰富的经验与借鉴。
First arrival seismic tomography(FAST) is one of the most widely used seismic tomography tools to achieve complicated three-dimensional(3D) deep crustal structure. The selection of optimal inversion parameters for FAST is a key to obtain a reasonable velocity model effectively. Based on the 3D seismic survey data collected from the central sub-basin of the South China Sea(SCS), the selection process of inversion parameters was illustrated in detail in this paper, using the control variate method, namely, selecting one parameter while fixing the other parameters, and then selecting the combination of all parameters comprehensively. The result showed that the combination of parameters(damping parameter λ=2, smoothness weighting parameter sz=1, inversion number I=4) was an assembly of optimal inversion parameters for the 3D seismic structure of the central sub-basin of the SCS. The preferred preliminary velocity structure acquired by this combination indicated that the central sub-basin could be classified as a typical slow-spreading oceanic crust. The research of choosing inversion parameters not only lays a foundation for further modeling of detailed 3D seismic structure of the Zhenbei-Huangyan seamount chain but also provides reference and experience for the application of FAST software in other potential areas.
First arrival seismic tomography(FAST) is one of the most widely used seismic tomography tools to achieve complicated three-dimensional(3D) deep crustal structure. The selection of optimal inversion parameters for FAST is a key to obtain a reasonable velocity model effectively. Based on the 3D seismic survey data collected from the central sub-basin of the South China Sea(SCS), the selection process of inversion parameters was illustrated in detail in this paper, using the control variate method, namely, selecting one parameter while fixing the other parameters, and then selecting the combination of all parameters comprehensively. The result showed that the combination of parameters(damping parameter λ=2, smoothness weighting parameter sz=1, inversion number I=4) was an assembly of optimal inversion parameters for the 3D seismic structure of the central sub-basin of the SCS. The preferred preliminary velocity structure acquired by this combination indicated that the central sub-basin could be classified as a typical slow-spreading oceanic crust. The research of choosing inversion parameters not only lays a foundation for further modeling of detailed 3D seismic structure of the Zhenbei-Huangyan seamount chain but also provides reference and experience for the application of FAST software in other potential areas.
引文
贾宇鹏.2012.初至波旅行时层析成像(FAST)方法研究和应用[D].兰州:中国地震局兰州地震研究所:34–46.
丘学林,赵明辉,叶春明,等.2003.南海东北部海陆联测与海底地震仪探测[J].大地构造与成矿学,27(4):295–300.
丘学林,赵明辉,徐辉龙,等.2012.南海深地震探测的重要科学进程:回顾和展望[J].热带海洋学报,31(3):1–8.
姚伯初,万玲,曾维军,等.2006.中国南海海域岩石圈三维结构及演化[M].北京:地质出版社:52–53.
赵明辉,丘学林,徐辉龙,等.2011.南海南部深地震探测及南北共轭陆缘对比[J].地球科学:中国地质大学学报,36(5):823–830.
张莉,赵明辉,王建,等.2013.南海中央次海盆OBS位置校正及三维地震探测新进展[J].地球科学:中国地质大学学报,8(1):33–42.
AKI K,LEE W.1976.Determination of three-dimensional velocityanomalies under a seismic array using first P arrival timesfrom local earthquakes:1.A homogeneous initial model[J].JGeophys Res,81(23):4381–4399.
BRIAIS A,PATRIAT P,TAPPONNIER P.1993.Updatedinterpretation of magnetic anomalies and seafloor spreadingstages in the South China Sea:Implications for the Tertiarytectonics of Southeast Asia[J].J Geophys Res,98(B4):6299–6328.
HOBRO J W,SINGH S C,MIMSHULL T A.2003.Threedimensional tomographic inversion of combined reflectionand refraction seismic traveltime data[J].Geophys J Int,152(1):79–93.
HOLE J A,ZELT B C.1995.3-D finite-difference reflectiontraveltimes[J].Geophys J Int,121(2):427–434.
MCINTOSH K,NAKAMURA Y,WANG TK,et al.2005.Crustal-scale seismic profiles across Taiwan and the westernPhilippine Sea[J].Tectonophysics,401(1):23–54.
PAIGE C C,SAUNDERS M A.1982.LSQR:An algorithm forsparse linear equations and sparse least squares[J].ACMTrans Math Softw,8(1):43–71.
RAMACHANDRAN K,DOSSO S,SPENCE G,et al.2005.Forearc structure beneath southwestern British Columbia:A three-dimensional tomographic velocity model[J].J GeophysRes,110(B2).doi:10.1029/2004JB003258.
RAMACHANDRAN K,HYNDMAN R,BROCHER T.2006.Regional P wave velocity structure of the Northern CascadiaSubduction Zone[J].J Geophys Res,111(B12).doi:10.1029/2005JB004108.
RODRIGUEZ-TABLANTE J I,JUHLIN C,BERGMAN B.2006.First arrival seismic tomography(FAST)vs.PStomo_eqapplied to crooked line seismic data from the Siljan ring area[J].Comput Geosci,32(4):497–511.
VIDALE J E.1988.Finite-difference calculation of travel times[J].Bull Seismol Soc Am,78(6):2062–2076.
VIDALE J E.1990.Finite-difference calculation of traveltimes inthree dimensions[J].Geophysics,55(5):521–526.
WHITE R S,MCKENZIE D,O'NIONS R K.1992.Oceaniccrustal thickness from seismic measurements and rare earthelement inversions[J].J Geophys Res,97(B13):19683–19715.
XU MIN,CANALES J P,TUCHOLKE B E,et al.2009.Heterogeneous seismic velocity structure of the upperlithosphere at Kane oceanic core complex,Mid-AtlanticRidge[J].Geochem Geophys Geosyst,10(10).doi:10.1029/2009GC002586.
ZELT C A,BARTON P J.1998.Three-dimensional seismicrefraction tomography:A comparison of two methods appliedto data from the Faeroe Basin[J].J Geophys Res,103(B4):7187–7210.
ZHAO MINGHUI,CANALES J P,SOHN R A.2012.Threedimensional seismic structure of a Mid-Atlantic Ridgesegment characterized by active detachment faulting(TransAtlantic Geotraverse,25°55′N-26°20′N)[J].Geochem GeophysGeosyst,13(1).doi:10.1029/2012GC004454.
丘学林,赵明辉,叶春明,等.2003.南海东北部海陆联测与海底地震仪探测[J].大地构造与成矿学,27(4):295–300.
丘学林,赵明辉,徐辉龙,等.2012.南海深地震探测的重要科学进程:回顾和展望[J].热带海洋学报,31(3):1–8.
姚伯初,万玲,曾维军,等.2006.中国南海海域岩石圈三维结构及演化[M].北京:地质出版社:52–53.
赵明辉,丘学林,徐辉龙,等.2011.南海南部深地震探测及南北共轭陆缘对比[J].地球科学:中国地质大学学报,36(5):823–830.
张莉,赵明辉,王建,等.2013.南海中央次海盆OBS位置校正及三维地震探测新进展[J].地球科学:中国地质大学学报,8(1):33–42.
AKI K,LEE W.1976.Determination of three-dimensional velocityanomalies under a seismic array using first P arrival timesfrom local earthquakes:1.A homogeneous initial model[J].JGeophys Res,81(23):4381–4399.
BRIAIS A,PATRIAT P,TAPPONNIER P.1993.Updatedinterpretation of magnetic anomalies and seafloor spreadingstages in the South China Sea:Implications for the Tertiarytectonics of Southeast Asia[J].J Geophys Res,98(B4):6299–6328.
HOBRO J W,SINGH S C,MIMSHULL T A.2003.Threedimensional tomographic inversion of combined reflectionand refraction seismic traveltime data[J].Geophys J Int,152(1):79–93.
HOLE J A,ZELT B C.1995.3-D finite-difference reflectiontraveltimes[J].Geophys J Int,121(2):427–434.
MCINTOSH K,NAKAMURA Y,WANG TK,et al.2005.Crustal-scale seismic profiles across Taiwan and the westernPhilippine Sea[J].Tectonophysics,401(1):23–54.
PAIGE C C,SAUNDERS M A.1982.LSQR:An algorithm forsparse linear equations and sparse least squares[J].ACMTrans Math Softw,8(1):43–71.
RAMACHANDRAN K,DOSSO S,SPENCE G,et al.2005.Forearc structure beneath southwestern British Columbia:A three-dimensional tomographic velocity model[J].J GeophysRes,110(B2).doi:10.1029/2004JB003258.
RAMACHANDRAN K,HYNDMAN R,BROCHER T.2006.Regional P wave velocity structure of the Northern CascadiaSubduction Zone[J].J Geophys Res,111(B12).doi:10.1029/2005JB004108.
RODRIGUEZ-TABLANTE J I,JUHLIN C,BERGMAN B.2006.First arrival seismic tomography(FAST)vs.PStomo_eqapplied to crooked line seismic data from the Siljan ring area[J].Comput Geosci,32(4):497–511.
VIDALE J E.1988.Finite-difference calculation of travel times[J].Bull Seismol Soc Am,78(6):2062–2076.
VIDALE J E.1990.Finite-difference calculation of traveltimes inthree dimensions[J].Geophysics,55(5):521–526.
WHITE R S,MCKENZIE D,O'NIONS R K.1992.Oceaniccrustal thickness from seismic measurements and rare earthelement inversions[J].J Geophys Res,97(B13):19683–19715.
XU MIN,CANALES J P,TUCHOLKE B E,et al.2009.Heterogeneous seismic velocity structure of the upperlithosphere at Kane oceanic core complex,Mid-AtlanticRidge[J].Geochem Geophys Geosyst,10(10).doi:10.1029/2009GC002586.
ZELT C A,BARTON P J.1998.Three-dimensional seismicrefraction tomography:A comparison of two methods appliedto data from the Faeroe Basin[J].J Geophys Res,103(B4):7187–7210.
ZHAO MINGHUI,CANALES J P,SOHN R A.2012.Threedimensional seismic structure of a Mid-Atlantic Ridgesegment characterized by active detachment faulting(TransAtlantic Geotraverse,25°55′N-26°20′N)[J].Geochem GeophysGeosyst,13(1).doi:10.1029/2012GC004454.
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