京津唐地区地壳三维P波速度结构与地震活动性分析
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摘要
本文利用华北遥测地震台网和首都圈数字地震台网112个台站记录到的1993～2004年发生在首都圈地区3983次地震的P波绝对到时资料和相对到时资料,采用双差地震层析成像方法联合反演了京津唐地区地壳三维P波速度结构和震源参数.京津唐地区的三维P波速度结构图像在浅层上很好地反映了地表地质、地形的特征.在平原和凹陷的盆地处呈现P波低速速度异常,而在隆起的山区或基岩出露区显示为P波高速速度异常.在研究区域内震级M≥6.0历史地震和经过重新定位后的震级M_L≥3.0的地震的震源位置在10 km深度和15 km深度处的P波相对速度扰动图上的投影都显示出相似的特点,即:绝大部分的地震的震源位置在P波相对速度扰动图上的投影分布在低、高速异常的交界地带,且偏高速体一侧,只有极少数的地震分布在P波速度异常体内部.
In this paper,we present a joint inversion investigation of both three-dimensional crustal P-wave structures and hypocenter parameters using double-difference seismic tomography method in Beijing-Tianjin-Tangshan (BTT) region.The double-difference seismic tomography method was adopted to refine the absolute and relative event locations and P-wave velocity structures simultaneously with the direct use of both absolute arrival times and the more accurate differential travel times.These data came from the earthquake catalog records of totally 3983 events recorded by 112 stations from the Northern China Telemetry Seismic Network (NCTSN) and Capital Digital Seismic Network (CDSN) in BTT region during the years of 1993 to 2004. The inversion results indicated that this method produced a more pronounced and detailed velocity model of the BTT region,which was more consistent with the features of the local geological setting.It revealed the low P-wave velocity anomaly in the plains and basins.In the uplifts of mountain and exposed rock areas,it appeared as high P-wave velocity anomalies.In the BTT region,after being projected to the horizontal P-wave relative velocity perturbation maps in 10 km and 15 km depths,the relocated hypocenters of magnitude M_L≥3.0 earthquakes showed identical features with those of the historic earthquakes with magnitude M≥6.0.The majority of the hypocenters were located in the conjunctional areas of low and high P-wave velocity anomalies. And they were slightly closer to the high P-wave velocity abnormal areas.Only few earthquakes have ever occurred within the high P-wave velocity anomalies.
In this paper,we present a joint inversion investigation of both three-dimensional crustal P-wave structures and hypocenter parameters using double-difference seismic tomography method in Beijing-Tianjin-Tangshan (BTT) region.The double-difference seismic tomography method was adopted to refine the absolute and relative event locations and P-wave velocity structures simultaneously with the direct use of both absolute arrival times and the more accurate differential travel times.These data came from the earthquake catalog records of totally 3983 events recorded by 112 stations from the Northern China Telemetry Seismic Network (NCTSN) and Capital Digital Seismic Network (CDSN) in BTT region during the years of 1993 to 2004. The inversion results indicated that this method produced a more pronounced and detailed velocity model of the BTT region,which was more consistent with the features of the local geological setting.It revealed the low P-wave velocity anomaly in the plains and basins.In the uplifts of mountain and exposed rock areas,it appeared as high P-wave velocity anomalies.In the BTT region,after being projected to the horizontal P-wave relative velocity perturbation maps in 10 km and 15 km depths,the relocated hypocenters of magnitude M_L≥3.0 earthquakes showed identical features with those of the historic earthquakes with magnitude M≥6.0.The majority of the hypocenters were located in the conjunctional areas of low and high P-wave velocity anomalies. And they were slightly closer to the high P-wave velocity abnormal areas.Only few earthquakes have ever occurred within the high P-wave velocity anomalies.
引文
[1] 金安蜀,刘福田,孙永智.北京地区地壳和上地幔的三维P波速度结构.地球物理学报,1980,23(2) :172～182 Jin A S,Liu F T,Sun Y Z.Three-dimensional P wave velocity structure of the crust and upper mantle under Beijing region.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1980,23(2) :172～182
[2] 刘福田,曲克信,吴华等.华北地区的地震层面成像.地球物理学报,1986,29(5) :442～449 Liu F T,Qu K X,Wu H,et al.Seismic tomography of North China region.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1986,29(5) :442～449
[3] Sheldlock K M,Roceker S W.Elastic wave velocity structure under the crust and upper mantle beneath the North China.J.Geophys.Res.,1987,92:9327～9350
[4] 朱露培,曾融生,刘福田.京津唐张地区地壳上地幔三维P波速度结构.地球物理学报,1990,33(3) :267～277 Zhu L P,Zeng R S,Liu F T.Three-dimensional P wave velocity structure under the Beijing network area.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1990,33(3) :267～277
[5] 丁志峰.近震层析成像的理论及应用[博士论文].北京:中国地震局地球物理研究所,1999． 154 Ding Z F.Regional seismic tomography:theory and applications[Ph.D.thesis](in Chinese).Beijing:Institute of Geophysics,China Earthquake Administration,1999． 154
[6] 于湘伟,陈运泰,王培德.京津唐地区中上地壳三维P波速度结构.地震学报,2003,25(1) :1～14 Yu X W,Chen Y T,Wang P D.Three-dimensional P wave velocity structure in Beijing-Tianjin-Tangshan area.Acta Seismologica Sinica(in Chinese),2003,25(1) :1～14
[7] 汪素云,许忠淮,裴顺平.华北地区上地幔顶部P_n波速度结构及其构造含义.中国科学,2003,33(增刊):91～98 Wang S Y,Xu Z H,Pei S P.Velocity structure of uppermost mantle beneath North China from Pn tomography and geological structure.Science in China(Series D)(in Chinese),2003,33(Suppl.):91～98
[8] Huang J L,Zhao D P.Crustal heterogeneity and seismotectonics of the region around Beijing,China.Tectonophysics,2005,385:159～180
[9] Huang J L,Zhao D P.Seismic imaging of the crust and upper mantle under Beijing and surrounding regions.Phys.Earth Planet.Interi.,2009,173:330～348
[10] Pei S P,Zhao J M,Sun Y S,et al.Upper mantle seismic velocities and anisotropy in China determined through Pn and Sn tomography.J.Geophys.Res.,2007,112,B05312,doi:10． 1029/2006JB004409
[11] Waldhauser F,Ellsworth W L.A double-difference earthquake location algorithm:method and application to the Northern Hayward Fault,California.Bull.Seism.Soc.Am.,2000,90:1353～1368
[12] Waldhauser F,Ellsworth W.Fault structure and mechanics of the California,from double-difference earthquake locations.J.Geophys.Res.,2002,107(B3) :ESE3-11～3-14
[13] 杨智娴,陈运泰,郑月军等.双差地震定位法在我国中西部地区地震精确定位中的应用.中国科学,2003,33(增刊):129～134 Yang Z X,Chen Y T,Zheng Y J,et al.Accurate relocation of earthquakes in central-western China using the double difference earthquake location algorithm.Science in China(Series D)(in Chinese),2003,33(Suppl.):129～134
[14] Yang Z X,Waldhauser F,Chen Y T,et al.Double-difference relocation of earthquakes in central-western China,1992～1999． Journal of Seismology,2005,9(2) :241～264
[15] 朱艾斓,徐锡伟,胡平等.首都圈地区地震重新定位及其在地震构造研究中的应用.地质论评,2005,51(3) :268～274 Zhu A L,Xu X W,Hu P,et al.Relocation of small earthquakes in Beijing area and its implication to seismotectonics.Geological Review(in Chinese),2005,51(3) :268～274
[16] 张宏志,刁桂苓,陈祺福等.1976年唐山7． 8级地震震区现今地震震源机制分析.地震研究,2008,31(1) :2～6 Zhang H Z,Diao G L,Chen Q F,et al.Focal mechanism analysis of the recent earthquakes in Tangshan seismic region of M7． 6 in 1976． Journal of Seismological Research(in Chinese),2008,31(1) :2～6
[17] Zhang H J,Thurber C H.Double difference tomography:the method and its application to the Hayward fault,California.Bull.Seism.Soc.Am.,2003,93(5) :1875～1889
[18] 滕吉文,姚虹,周海南.北京、天津、唐山和张家口地区的地壳结构.地球物理学报,1979,22(3) :218～236 Teng J W,Yao H,Zhou H N.Crustal structure in the Beijing-Tianjin-Tangshan-Zhangjiakou region.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1979,22(3) :218～236
[19] Leveque J,Rivera L,Wittlinger G.On the use of the checkerboard test to assess the resolution of tomographic inversions.Geophys.J.Int.,1993,115:313～318
[20] 高文学,马瑾.首都圈地震地质环境与地震灾害.北京:地震出版社,1993． 452 Gao W X,Ma J.Seismo-Geological Background and Earthquake Hazard in Beijing Area(in Chinese).Beijing:Seismological Press,1993． 452
[21] 于湘伟,陈运泰,张怀.京津唐地区中小地震重定位结果及对比.地震学报,2010,32(3) :257～269 Yu X W,Chen Y T,Zhang H.Relocation of earthquakes in Beijing-Tianjin-Tangshan region by double-difference tomography technique.Acta Seismologica Sinica(in Chinese),2010,32(3) :257～269
[22] 藏绍先,杨军亮.我国华北等地区板内地震的深度分布及其物理背景.地震地质,1984,6(5) :67～75 Zang S X,Yang J L.The depth distribution of North China intraplate earthquakes and their physical background.Seismol.Geol.,1984,6(5) :67～75
[2] 刘福田,曲克信,吴华等.华北地区的地震层面成像.地球物理学报,1986,29(5) :442～449 Liu F T,Qu K X,Wu H,et al.Seismic tomography of North China region.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1986,29(5) :442～449
[3] Sheldlock K M,Roceker S W.Elastic wave velocity structure under the crust and upper mantle beneath the North China.J.Geophys.Res.,1987,92:9327～9350
[4] 朱露培,曾融生,刘福田.京津唐张地区地壳上地幔三维P波速度结构.地球物理学报,1990,33(3) :267～277 Zhu L P,Zeng R S,Liu F T.Three-dimensional P wave velocity structure under the Beijing network area.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1990,33(3) :267～277
[5] 丁志峰.近震层析成像的理论及应用[博士论文].北京:中国地震局地球物理研究所,1999． 154 Ding Z F.Regional seismic tomography:theory and applications[Ph.D.thesis](in Chinese).Beijing:Institute of Geophysics,China Earthquake Administration,1999． 154
[6] 于湘伟,陈运泰,王培德.京津唐地区中上地壳三维P波速度结构.地震学报,2003,25(1) :1～14 Yu X W,Chen Y T,Wang P D.Three-dimensional P wave velocity structure in Beijing-Tianjin-Tangshan area.Acta Seismologica Sinica(in Chinese),2003,25(1) :1～14
[7] 汪素云,许忠淮,裴顺平.华北地区上地幔顶部P_n波速度结构及其构造含义.中国科学,2003,33(增刊):91～98 Wang S Y,Xu Z H,Pei S P.Velocity structure of uppermost mantle beneath North China from Pn tomography and geological structure.Science in China(Series D)(in Chinese),2003,33(Suppl.):91～98
[8] Huang J L,Zhao D P.Crustal heterogeneity and seismotectonics of the region around Beijing,China.Tectonophysics,2005,385:159～180
[9] Huang J L,Zhao D P.Seismic imaging of the crust and upper mantle under Beijing and surrounding regions.Phys.Earth Planet.Interi.,2009,173:330～348
[10] Pei S P,Zhao J M,Sun Y S,et al.Upper mantle seismic velocities and anisotropy in China determined through Pn and Sn tomography.J.Geophys.Res.,2007,112,B05312,doi:10． 1029/2006JB004409
[11] Waldhauser F,Ellsworth W L.A double-difference earthquake location algorithm:method and application to the Northern Hayward Fault,California.Bull.Seism.Soc.Am.,2000,90:1353～1368
[12] Waldhauser F,Ellsworth W.Fault structure and mechanics of the California,from double-difference earthquake locations.J.Geophys.Res.,2002,107(B3) :ESE3-11～3-14
[13] 杨智娴,陈运泰,郑月军等.双差地震定位法在我国中西部地区地震精确定位中的应用.中国科学,2003,33(增刊):129～134 Yang Z X,Chen Y T,Zheng Y J,et al.Accurate relocation of earthquakes in central-western China using the double difference earthquake location algorithm.Science in China(Series D)(in Chinese),2003,33(Suppl.):129～134
[14] Yang Z X,Waldhauser F,Chen Y T,et al.Double-difference relocation of earthquakes in central-western China,1992～1999． Journal of Seismology,2005,9(2) :241～264
[15] 朱艾斓,徐锡伟,胡平等.首都圈地区地震重新定位及其在地震构造研究中的应用.地质论评,2005,51(3) :268～274 Zhu A L,Xu X W,Hu P,et al.Relocation of small earthquakes in Beijing area and its implication to seismotectonics.Geological Review(in Chinese),2005,51(3) :268～274
[16] 张宏志,刁桂苓,陈祺福等.1976年唐山7． 8级地震震区现今地震震源机制分析.地震研究,2008,31(1) :2～6 Zhang H Z,Diao G L,Chen Q F,et al.Focal mechanism analysis of the recent earthquakes in Tangshan seismic region of M7． 6 in 1976． Journal of Seismological Research(in Chinese),2008,31(1) :2～6
[17] Zhang H J,Thurber C H.Double difference tomography:the method and its application to the Hayward fault,California.Bull.Seism.Soc.Am.,2003,93(5) :1875～1889
[18] 滕吉文,姚虹,周海南.北京、天津、唐山和张家口地区的地壳结构.地球物理学报,1979,22(3) :218～236 Teng J W,Yao H,Zhou H N.Crustal structure in the Beijing-Tianjin-Tangshan-Zhangjiakou region.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1979,22(3) :218～236
[19] Leveque J,Rivera L,Wittlinger G.On the use of the checkerboard test to assess the resolution of tomographic inversions.Geophys.J.Int.,1993,115:313～318
[20] 高文学,马瑾.首都圈地震地质环境与地震灾害.北京:地震出版社,1993． 452 Gao W X,Ma J.Seismo-Geological Background and Earthquake Hazard in Beijing Area(in Chinese).Beijing:Seismological Press,1993． 452
[21] 于湘伟,陈运泰,张怀.京津唐地区中小地震重定位结果及对比.地震学报,2010,32(3) :257～269 Yu X W,Chen Y T,Zhang H.Relocation of earthquakes in Beijing-Tianjin-Tangshan region by double-difference tomography technique.Acta Seismologica Sinica(in Chinese),2010,32(3) :257～269
[22] 藏绍先,杨军亮.我国华北等地区板内地震的深度分布及其物理背景.地震地质,1984,6(5) :67～75 Zang S X,Yang J L.The depth distribution of North China intraplate earthquakes and their physical background.Seismol.Geol.,1984,6(5) :67～75
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