唐山地震深浅构造关系研究
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摘要
地表观察和浅层高分辨率地震探测表明 ,唐山断裂与地震地表主破裂带的位置、产状均一致 ,且具有高角度西倾的逆冲走滑性质 ,发生过右旋水平错动和向东逆冲的垂直活动 ,而次破裂带与褶皱构造活动引起的其他断裂直接相关。根据瞬变磁场和深地震探测结果分析 ,唐山地区存在莫霍面斜坡和地壳“背斜”、中地壳水平滑脱和扩展断裂、上地壳高角度逆冲走滑断裂和背向斜构造 ,它们组成 1幅多层次、多级序的复式逆断裂 -扩展背斜构造图像 ,控制了唐山地震的孕育和发生。
In this paper, field observation on earthquake surface rupture zone and high-resolution seismic reflection profiling of faults in combination with related geological data have led to some new insights about shallow Quaternary geology and underground fault structure in the 1976 Tangshan earthquake area. On this basis, we analyze prospecting results of deep structure and then study the relationship between deep and shallow structures in the 1976 Tangshan earthquake area, as well discuss tectonic setting and seismogenic model for this earthquake. Tanshan fault zone is a complex structure zone associated with faults and folds in this area. It is mainly developed on southeastern flank of an anticline and northwest flank of the Kaiping syncline, and consists of a series of NNE-NE-trending parallel faults. This fault zone can be divided into southern and northern segments and/or bifurcated into eastern and western branches, controlling seismic activity and geological motion in this area. The eastern branch of southern segment of this fault zone is Tangshan Fault, which strikes to N30°E and consists of two parallel faults. The eastern fault dips to WNW at an angle of 70°～80° and represents the main fault with reverse-strike-slipping. The 1976 Tangshan M 7.8 earthquake produced four surface rupture zones. The main surface rupture zone is ～8km long and generally strikes to N30°E. It consists of many secondary right-lateral en echelon ground fissure zones on both southern and northern segments, distributed along Tangshan Fault. This surface rupture zone underwent horizontal and vertical dislocations, with horizontal separation of 1.53m in maximum and vertical offset of 0.2～0.7m. The western side of this zone has been uplifted and the eastern side subsided. The high-resolution seismic reflection profiling revealed the following relations between Tangshan Fault and earthquake surface rupture zone: (1) their positions are consistent; (2) their geometric attitudes are consistent, dips to west at angle of 70°～80°; (3) their movements are of reverse-strike-slip faulting, while strong-reflection interfaces show a compressive bending and strike-slip motion characters. These facts indicate that there exists a high-angle reverse strike-slip fault, i.e. the NNE-trending and WNW-dipping Tangshan Fault, the sudden motion of which produced the 1976 Tangshan M 7.8 earthquake. The high-resolution seismic reflection profiling also revealed a SE-dipping reverse fault with a dip angle of about 70°. It occurs on the western steep limb of the Kaiping syncline east of the Tangshan Fault, and may be a shallow bending-slip or bending-moment fault, on which a ground fissure zone produced by the 1976 Tangshan earthquake. Analysis on deep seismic sounding result indicates that the relation between shallow and deep structures is close in spatial location, geometric structure and movement nature. There exist W-dipping slope of the Moho discontinuity, crustal "anticline", horizontal detachment and propagation fault in the middle crust, high-angle reverse-strike-slip fault and fold structure in the upper crust. They form a structural pattern of multi-order and multi-step composite fault-propagation fold, and controll the tectonic deformation and seismic activity in this area. The 1976 Tangshan earthquake is a result of stick-slipping along Tangshan Fault zone caused by the detachment and fault-propagation in the middle crust and by the stress concentration on the base of upper crust. The cumulative vertical offset has reached 15m along the Tangshan Fault since the late Pleistocene. The vertical offset of ground is 0.3m caused by the Tangshan earthquake and 0.5m obtained by inversion of seismic wave data. If creepslip is not taken into account, the recurrence interval of earthquakes on the Tangshan Fault is 2.4～4.0ka, which is comparable with the result of regional paleo-seismological research.
In this paper, field observation on earthquake surface rupture zone and high-resolution seismic reflection profiling of faults in combination with related geological data have led to some new insights about shallow Quaternary geology and underground fault structure in the 1976 Tangshan earthquake area. On this basis, we analyze prospecting results of deep structure and then study the relationship between deep and shallow structures in the 1976 Tangshan earthquake area, as well discuss tectonic setting and seismogenic model for this earthquake. Tanshan fault zone is a complex structure zone associated with faults and folds in this area. It is mainly developed on southeastern flank of an anticline and northwest flank of the Kaiping syncline, and consists of a series of NNE-NE-trending parallel faults. This fault zone can be divided into southern and northern segments and/or bifurcated into eastern and western branches, controlling seismic activity and geological motion in this area. The eastern branch of southern segment of this fault zone is Tangshan Fault, which strikes to N30°E and consists of two parallel faults. The eastern fault dips to WNW at an angle of 70°～80° and represents the main fault with reverse-strike-slipping. The 1976 Tangshan M 7.8 earthquake produced four surface rupture zones. The main surface rupture zone is ～8km long and generally strikes to N30°E. It consists of many secondary right-lateral en echelon ground fissure zones on both southern and northern segments, distributed along Tangshan Fault. This surface rupture zone underwent horizontal and vertical dislocations, with horizontal separation of 1.53m in maximum and vertical offset of 0.2～0.7m. The western side of this zone has been uplifted and the eastern side subsided. The high-resolution seismic reflection profiling revealed the following relations between Tangshan Fault and earthquake surface rupture zone: (1) their positions are consistent; (2) their geometric attitudes are consistent, dips to west at angle of 70°～80°; (3) their movements are of reverse-strike-slip faulting, while strong-reflection interfaces show a compressive bending and strike-slip motion characters. These facts indicate that there exists a high-angle reverse strike-slip fault, i.e. the NNE-trending and WNW-dipping Tangshan Fault, the sudden motion of which produced the 1976 Tangshan M 7.8 earthquake. The high-resolution seismic reflection profiling also revealed a SE-dipping reverse fault with a dip angle of about 70°. It occurs on the western steep limb of the Kaiping syncline east of the Tangshan Fault, and may be a shallow bending-slip or bending-moment fault, on which a ground fissure zone produced by the 1976 Tangshan earthquake. Analysis on deep seismic sounding result indicates that the relation between shallow and deep structures is close in spatial location, geometric structure and movement nature. There exist W-dipping slope of the Moho discontinuity, crustal "anticline", horizontal detachment and propagation fault in the middle crust, high-angle reverse-strike-slip fault and fold structure in the upper crust. They form a structural pattern of multi-order and multi-step composite fault-propagation fold, and controll the tectonic deformation and seismic activity in this area. The 1976 Tangshan earthquake is a result of stick-slipping along Tangshan Fault zone caused by the detachment and fault-propagation in the middle crust and by the stress concentration on the base of upper crust. The cumulative vertical offset has reached 15m along the Tangshan Fault since the late Pleistocene. The vertical offset of ground is 0.3m caused by the Tangshan earthquake and 0.5m obtained by inversion of seismic wave data. If creepslip is not taken into account, the recurrence interval of earthquakes on the Tangshan Fault is 2.4～4.0ka, which is comparable with the result of regional paleo-seismological research.
引文
①方鸿琪,王锺琦,赵树栋等,1981,唐山强震区地震工程地质研究。
①参加浅层地震探测的还有楼海,吴庆举,贺伟松,杨春生等。
杜春涛,孟宪梁,陈书贤.1985.唐山地震的地裂缝〔M〕.见:刘恢先主编.唐山大地震震害(一).北京:地震出版社.174—189.
DUChun tao,MENGXian liang,CHENShu xian.1985.GroundfissurescausedbyTangshanearthquake〔M〕.In:LIUHui xian(ed).DisasterofTangshanGreatEarthquake(1).SeismologicalPress,Beijing.174—189(inChinese).
桂琨长,耿世昌.1987.值得再三思考的唐山地震构造〔J〕.中国地震,3(增刊):79—84.
GUIKun chang,GENGShi chang.1987.Worthwhileconsideringtheseismo structureoftheTangshanearthquake〔J〕.EarthquakeResearchinChina,3(suppl):79—84(inChinese).
虢顺民,李志义,程绍平,等.1977.唐山地震区域构造背景和发震模式的讨论〔J〕.地质科学,4:305—320.
GUOShun min,LIZhi yi,CHENGShao ping,etal.1977.AdiscussiononregionalstructuresandearthquakemodelinTangshanseismicarea〔J〕.ScientiaGeologicaSinica,4:305—320(inChinese).
国家地震局.1977.中国强震简目〔Z〕.北京:地震出版社.
StateSeismologicalBureau.1977.CatalogueofStrongEarthquakesinChina〔Z〕.SeismologicalPress,Beijing(inChinese).
国家地震局《一九七六年唐山地震》编辑组.1982.一九七六年唐山地震〔M〕.北京:地震出版社.4—23.
EditorialGroupof“The1976TangshanEarthquake”,StateSeismologicalBureau.1982.The1976TangshanEarth quake〔M〕.SeismologicalPress,Beijing.4—23(inChinese).
李绍炳.1986.唐山地震的发震构造与成因的探讨〔J〕.华北地震科学,4(2):56—62.
LIShao bing.1986.Adiscussionoftheseismo tectonicsandthecauseofTangshanearthquake〔J〕.NorthChinaEarthquakeSciences,4(2):56—62(inChiense).
刘昌铨,嘉世旭.1986.唐山地震区地壳上地幔结构特征:二维非均匀介质中理论地震图计算和结果分析〔J〕.地震学报,8(4):341—353.
IUChang quan,JIAShi xu.1986.StructuralpropertyofthecrustandtheuppermantleintheTangshanearth quakeregion:Amethodofcomputingbodywavetheoreticalseismogramandtheresultofanalysisof2Dinho mogeneousmedia〔J〕.ActaSeismologicaSinica,8(4):341—353(inChinese).
刘国栋.1994.唐山地震震源构造及动力学过程研究〔A〕.见:国家地震局地质研究所编.现今地球动力学研究及其应用.北京:地震出版社.70—83.
LIUGuo dong.1994.ResearchonfocusstructuresanddynamicalprocessofTangshanearthquake.In:InstituteofGeology,StateSeismologicalBureau(ed).ResearchonModernGeodynamicsandItsApplication〔A〕.Seismo logicalPress,Beijing.70—83(inChinese).
刘英武,李龙海,吴建华,等.1996.从地球化学角度讨论1976年唐山7.8级地震的成因〔J〕.地质地球化学,5:66—69.
IUYing wu,LILong hai,WUJian hua,etal.1996.Genesisofthe1976TangshanM 7.8earthquakediscussedbygeochemistry〔J〕.Geology chemistry,5:66—69(inChinese).
陆涵行,曾融生,郭建明,等.1988.唐山震区可控震源深反射剖面结果分析〔J〕.地球物理学报,31(1):27—36.
LUHan xing,ZENGRong sheng,GUOJian ming,etal.1988.ResultsfromdeepseismicreflectionprofilinginTangshanregion〔J〕.ActaGeophysicaSinica,31(1):27—36(inChinese).
马瑾,张渤涛,袁淑荣.1980.唐山地震与地震危险区〔J〕.地震地质,2(2):43—54.
MAJin,ZHANGBo tao,YUANShu rong.1980.Tangshanearthquakeandtheearthquakeriskarea〔J〕.Seismol ogyandGeology,2(2):43—54(inChinese).
马宗晋,傅征祥,张郢珍,等.1982.1966—1976年中国九大地震〔M〕.北京:地震出版社.11—24.
MAZong jin,FUZheng xiang,ZHANGYing zhen,etal.1982.NineMajorEarthquakesinChina(1966—1976)〔M〕.SeismologicalPress,Beijing.11—24(inChinese).
强祖基,张立人.1982.唐山地震与第四纪活动断裂〔A〕.见:中国地震学会地震地质专业委员会编.中国活动断裂.北京:地震出版社.67—71.
QIANGZhu ji,ZHANGLi ren.1982.TangshanearthquakeandQuaternaryactivefaults〔A〕.In:Seismo geologi calCommitteeofChineseSeismologicalSociety(ed).ActiveFaultsinChina.SeismologicalPress,Beijing.67—71(inChinese).
邱群.1976.1976年7月28日河北省唐山7.8级地震的发震背景及其活动性〔J〕.地球物理学报,19(4):259—269.
QIUQun.1976.OnthebackgroundandseismicactivityoftheM 7.8Tangshanearthquake,HepeiprovinceofJuly28,1976〔J〕.ActaGeophysicaSinica,19(4):259—269(inChinese).
唐山地震工作队.1977.唐山大震发震构造〔J〕.地震战线,2:5—7.
TangshanSeismologicalTeam.1977.SeismotectonicsofTangshanearthquake〔J.DizhenZhajxian,2:5—7(inChinese).
王景明.1980.1976年唐山地震地下工程震害的分布规律〔J〕.地震学报,2(3):314—320.
WANGJing ming.1980.Distributionofundergroundseismicintensityi
①参加浅层地震探测的还有楼海,吴庆举,贺伟松,杨春生等。
杜春涛,孟宪梁,陈书贤.1985.唐山地震的地裂缝〔M〕.见:刘恢先主编.唐山大地震震害(一).北京:地震出版社.174—189.
DUChun tao,MENGXian liang,CHENShu xian.1985.GroundfissurescausedbyTangshanearthquake〔M〕.In:LIUHui xian(ed).DisasterofTangshanGreatEarthquake(1).SeismologicalPress,Beijing.174—189(inChinese).
桂琨长,耿世昌.1987.值得再三思考的唐山地震构造〔J〕.中国地震,3(增刊):79—84.
GUIKun chang,GENGShi chang.1987.Worthwhileconsideringtheseismo structureoftheTangshanearthquake〔J〕.EarthquakeResearchinChina,3(suppl):79—84(inChinese).
虢顺民,李志义,程绍平,等.1977.唐山地震区域构造背景和发震模式的讨论〔J〕.地质科学,4:305—320.
GUOShun min,LIZhi yi,CHENGShao ping,etal.1977.AdiscussiononregionalstructuresandearthquakemodelinTangshanseismicarea〔J〕.ScientiaGeologicaSinica,4:305—320(inChinese).
国家地震局.1977.中国强震简目〔Z〕.北京:地震出版社.
StateSeismologicalBureau.1977.CatalogueofStrongEarthquakesinChina〔Z〕.SeismologicalPress,Beijing(inChinese).
国家地震局《一九七六年唐山地震》编辑组.1982.一九七六年唐山地震〔M〕.北京:地震出版社.4—23.
EditorialGroupof“The1976TangshanEarthquake”,StateSeismologicalBureau.1982.The1976TangshanEarth quake〔M〕.SeismologicalPress,Beijing.4—23(inChinese).
李绍炳.1986.唐山地震的发震构造与成因的探讨〔J〕.华北地震科学,4(2):56—62.
LIShao bing.1986.Adiscussionoftheseismo tectonicsandthecauseofTangshanearthquake〔J〕.NorthChinaEarthquakeSciences,4(2):56—62(inChiense).
刘昌铨,嘉世旭.1986.唐山地震区地壳上地幔结构特征:二维非均匀介质中理论地震图计算和结果分析〔J〕.地震学报,8(4):341—353.
IUChang quan,JIAShi xu.1986.StructuralpropertyofthecrustandtheuppermantleintheTangshanearth quakeregion:Amethodofcomputingbodywavetheoreticalseismogramandtheresultofanalysisof2Dinho mogeneousmedia〔J〕.ActaSeismologicaSinica,8(4):341—353(inChinese).
刘国栋.1994.唐山地震震源构造及动力学过程研究〔A〕.见:国家地震局地质研究所编.现今地球动力学研究及其应用.北京:地震出版社.70—83.
LIUGuo dong.1994.ResearchonfocusstructuresanddynamicalprocessofTangshanearthquake.In:InstituteofGeology,StateSeismologicalBureau(ed).ResearchonModernGeodynamicsandItsApplication〔A〕.Seismo logicalPress,Beijing.70—83(inChinese).
刘英武,李龙海,吴建华,等.1996.从地球化学角度讨论1976年唐山7.8级地震的成因〔J〕.地质地球化学,5:66—69.
IUYing wu,LILong hai,WUJian hua,etal.1996.Genesisofthe1976TangshanM 7.8earthquakediscussedbygeochemistry〔J〕.Geology chemistry,5:66—69(inChinese).
陆涵行,曾融生,郭建明,等.1988.唐山震区可控震源深反射剖面结果分析〔J〕.地球物理学报,31(1):27—36.
LUHan xing,ZENGRong sheng,GUOJian ming,etal.1988.ResultsfromdeepseismicreflectionprofilinginTangshanregion〔J〕.ActaGeophysicaSinica,31(1):27—36(inChinese).
马瑾,张渤涛,袁淑荣.1980.唐山地震与地震危险区〔J〕.地震地质,2(2):43—54.
MAJin,ZHANGBo tao,YUANShu rong.1980.Tangshanearthquakeandtheearthquakeriskarea〔J〕.Seismol ogyandGeology,2(2):43—54(inChinese).
马宗晋,傅征祥,张郢珍,等.1982.1966—1976年中国九大地震〔M〕.北京:地震出版社.11—24.
MAZong jin,FUZheng xiang,ZHANGYing zhen,etal.1982.NineMajorEarthquakesinChina(1966—1976)〔M〕.SeismologicalPress,Beijing.11—24(inChinese).
强祖基,张立人.1982.唐山地震与第四纪活动断裂〔A〕.见:中国地震学会地震地质专业委员会编.中国活动断裂.北京:地震出版社.67—71.
QIANGZhu ji,ZHANGLi ren.1982.TangshanearthquakeandQuaternaryactivefaults〔A〕.In:Seismo geologi calCommitteeofChineseSeismologicalSociety(ed).ActiveFaultsinChina.SeismologicalPress,Beijing.67—71(inChinese).
邱群.1976.1976年7月28日河北省唐山7.8级地震的发震背景及其活动性〔J〕.地球物理学报,19(4):259—269.
QIUQun.1976.OnthebackgroundandseismicactivityoftheM 7.8Tangshanearthquake,HepeiprovinceofJuly28,1976〔J〕.ActaGeophysicaSinica,19(4):259—269(inChinese).
唐山地震工作队.1977.唐山大震发震构造〔J〕.地震战线,2:5—7.
TangshanSeismologicalTeam.1977.SeismotectonicsofTangshanearthquake〔J.DizhenZhajxian,2:5—7(inChinese).
王景明.1980.1976年唐山地震地下工程震害的分布规律〔J〕.地震学报,2(3):314—320.
WANGJing ming.1980.Distributionofundergroundseismicintensityi
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