中朝地台东北缘地区的地震层析成像
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摘要
根据中朝地台东北缘地区 (东经 1 1 7°0 0′— 1 2 6°0 0′ ,北纬 36°0 0′— 44°0 0′) 1 980— 1 997年的 380 0 0余条P波走时数据 ,利用正交投影法重建了该区地壳和上地幔的三维速度结构 .通过分析及同人工地震测深剖面的详细对比 ,证明了成像结果的可靠性 .结果表明 :中朝地台东北缘地区地壳上地幔介质存在显著的横向不均匀性 ,直至 1 2 0km深度处依然明显 ;地壳上部的速度图像清楚地反映了不同岩石单元的分布与该区不同性质的基岩分布基本吻合 ;从上、中地壳的速度图像中发现了研究区存在海城、朝阳、义县、丹东南、唐山等几个低速异常区(即速度逆反层区 ) ,其中海城、唐山、朝阳等地区的壳内低速层已由深地震测深资料所证实 ;研究区陆地发生的几次强震均发生于壳内低速层上方的高速脆性介质内 ,而渤海发生的强震 ,此现象不明显 ,但都发生于横向介质速度显著突变的位置 ;在地壳不同深度上发现了普兰店至山海关横跨渤海的北西向低速异常带 ;地震层析二维速度图像与深地震测深资料的对比表明 ,研究区利用地震层析成像技术 ,在一定条件下可以获得与人工地震测深相似的效果
Based on 38?000 P wave arrival times recorded during the period of 1980 to 1997 in the northeast margin area of Sino Korean platform (117°00′\_126°00′E, 36°00′\_44°00′N) the 3D velocity structures of the crust and upper mantle have been reconstructed by using orthogonal projection. The tomography results have been proved to be reliable by analyzing and comparing in detail the results with the deep seismic prospecting profiles. It is shown that there exists obvious lateral inhomogeneity in the medium of the crust and upper mantle which is still distinct even at the 120km depth in the northeast margin area of Sino Korean platform. It is reflected clearly in the velocity image of the upper crust that the distribution of all kinds of rock elements corresponds to that of rocks with different nature in this area. Several lower velocity anomaly regions (i.e. regions with velocity reversed layer) have been discovered in the studied area from the velocity images of upper and middle crust, such as Haicheng, Chaoyang?Yixian, south of Dandong, Tangshan etc., among which the lower velocity layers in Haicheng, Tangshan, Chaoyang have also been proved by the deep seismic sounding data. In the area several strong continental earthquakes all happened in crispy medium with higher velocity above lower velocity layers in the crust, whereas in Bohai sea all strong earthquakes happened in positions where the medium velocity changes abruptly and clearly in horizontal. At different depth, Pulandian Shanhaiguan lower velocity anomaly zone across Bohai sea with strike NW has been found. Comparison of the velocity images obtained from 2D seismic tomography with that from deep seismic sounding data, we can consider to gain similar effect with deep seismic sounding by taking advantage of seismic tomography under certain condition in this area.
Based on 38?000 P wave arrival times recorded during the period of 1980 to 1997 in the northeast margin area of Sino Korean platform (117°00′\_126°00′E, 36°00′\_44°00′N) the 3D velocity structures of the crust and upper mantle have been reconstructed by using orthogonal projection. The tomography results have been proved to be reliable by analyzing and comparing in detail the results with the deep seismic prospecting profiles. It is shown that there exists obvious lateral inhomogeneity in the medium of the crust and upper mantle which is still distinct even at the 120km depth in the northeast margin area of Sino Korean platform. It is reflected clearly in the velocity image of the upper crust that the distribution of all kinds of rock elements corresponds to that of rocks with different nature in this area. Several lower velocity anomaly regions (i.e. regions with velocity reversed layer) have been discovered in the studied area from the velocity images of upper and middle crust, such as Haicheng, Chaoyang?Yixian, south of Dandong, Tangshan etc., among which the lower velocity layers in Haicheng, Tangshan, Chaoyang have also been proved by the deep seismic sounding data. In the area several strong continental earthquakes all happened in crispy medium with higher velocity above lower velocity layers in the crust, whereas in Bohai sea all strong earthquakes happened in positions where the medium velocity changes abruptly and clearly in horizontal. At different depth, Pulandian Shanhaiguan lower velocity anomaly zone across Bohai sea with strike NW has been found. Comparison of the velocity images obtained from 2D seismic tomography with that from deep seismic sounding data, we can consider to gain similar effect with deep seismic sounding by taking advantage of seismic tomography under certain condition in this area.
引文
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[16] 卢造勋.中国海城地震与地壳上地幔异常结构.长春地质学院学报,1992,22(4):454—459.LUZaoXun.HaichengearthquakeinChinaanditsrelationstoabnormaltectonicsofthecrustanduppermantle.JournalofChangchunGeologyCollege,1992,22(4):454—459.
[17] 雷清清,孟补在,牛 雪等.中朝地台东北缘3km深度地震层析成像的地质解释.东北地震研究,1999,15(1):37—45.LEIQingQing,MENGBuZai,NIUXue,etal.Geologicalinterpretationofseismo tomographyImage3kminnortheastedgeofSinoKoreanplatform.SeismologicalResearchofNortheastChina,1999,15(1):37—45.
[18] 姜德录,白 云,卢造勋.中朝地台东北缘及其邻区软流圈分布特征与构造运动的关系.东北地震研究,2000,16(1):14—25.JIANGDeLu,BAIYun,LUZaoXun,TheasthenospheredistributionfeaturesandtherelationtotectonicactivitiesintheareaofnortheastmarginofSinoKoreanplatformanditsneighboringarea.SeismologicalResearchofNortheastChina,2000,16(1):14—25.
[19] 卢造勋,刘国栋,位梦华等.辽南地区地壳与上地幔介质的横向不均匀性与海城7.3级地震.地震学报,1990,12(4):367—378.LUZaoXun,LIUGuoDong,WEIMengHua,etal.LateralinhomogeneityofthecrustanduppermantleinsouthLiaoning,Chinaandit’srelationshipwiththeMs=7.3Haichenearthquake.ActaSeismologicaSinica,1990,12(4):367—378.
[20] 夏怀宽,卢造勋,牛 雪等.海城、朝阳地震区的岩石圈特征.见:卢造勋等编,发展中的地震科学研究.北京:地震出版社,1995.158—164.XIAHuaiKuan,LUZaoXun,NIUXueetal.ThecharacteristicsofthelithosphereinHaichengandChaoyangseismicarea,Liaoning.In:LUZaoXunetal.ed,ProceedingsofSymposiumonEarthquakeResearch.Beijing:SeismologicalPress,1995.158—164.
[21] 卢造勋,潘 科,蒋秀琴等.胶辽渤海地区地壳上地幔结构特征与地震活动.活动断裂研究,2001,8:9—31.LUZaoXun,PANKe,JIANGXiuQin,etal.StructureChateristicsofthecrustanduppermantleandseismicityintheJiaoliaoandBohaiSeaarea.ResearchonActiveFault,2001,8:9—31.
[22] 赵俊猛,卢造勋.辽河裂谷的深部构造与裂谷活动的侧向迁移.地震地质,1998,20(3):225—233.ZHAOJunMeng,LUZaoXun.DeepstructureofLiaoheriftvalleyandeastwardmigration.Seismogeology,1998,20(3):225—233.
[2] Aki,K .,Christoffersson,A .andHusebye,ES .Determinationofthethree dimentionalseismicstructureofthelithosphere.J.Geophys.Res.,1977,82:277—296.
[3] 张先康,杨玉春,赵 平等.唐山滦县震区的三维地震透射研究中、上地壳速度层析成像.地球物理学报,1994,37(6):759—766.ZHANGXianKang,YANGYuChun,ZHAOPingetal.ThreeDimensionalSeismictransimissionexperimentintheLuanxianCountyearthquakeregionofNorthChina:tomographydeterminationoftheupperandmiddlecruststructure.ChineseJ.Geophys.(ActaGeophysicaSinica),1994,37(6):759—766.
[4] 刘福田,李 强,吴 华等.用于速度图像重建的层析成像.地球物理学报,1989,32(1):46—61.LIUFuTian,LIQiang,WUHuaetal.Onthetomographyinversemethodusedinvelocityimagereconstruction.ChineseJ.Geophys.(ActaGeophysicaSinica),1989,32(1):46—61.
[5] Tarantola,A .,Nercessian,A .Three dimensionalinversionwithoutblocks.Geophys.J.R .astr.Soc.,1984,76:299—306.
[6] ZHANGXianKang,YANGZhuo xin,YANGYu chun,etal.Tomographicdeterminationof3DcrustalstructureJointinversionofexplosionandearthquakedata.Actaseismologicasinica,1995,8(4):519—529.
[7] 卢造勋.海城震区的深部地球物理探测.中国地震,1995,1(1):56—65.LUZaoXun.ProgressofgeophysicalprospectingstudyonthedeepstructureofHaichengearthquakearea.EarthquakeResearchinChina(inChinese),1995,1(1):56—65.
[8] 孙若昧,赵燕来,梅世蓉.渤海及其邻区的地震层析成像.地球物理学报,1993,36(1):44—54.SUNRuoMei,ZHAOYanLai,MEIShiRong.SeismicTomographicimageinBohaiseaanditsadjacentarea.ChineseJ.Geophys.(ActaGeophysicaSinica),1993,36(1):44—54.
[9] 滕吉文,张中杰,张秉铭等.渤海地球物理场与深部潜在地幔热柱的异常背景.地球物理学报,1997,40(4):468—480.TENGJiWen,ZHANGZhongJie,ZHANGBingMingetal.GeophysicalfieldsandbackgroundofexceptionalstructurefordeeplatentmantleplumeinBohaiSea.ChineseJ .Geophys.(ActaGeophysicaSinica),1997,40(4):468—480.
[10] 卢造勋,夏怀宽.内蒙古东乌珠穆沁旗至辽宁东沟地学断面.地球物理学报,1993,36(6):765—772.LUZaoXun,XIAHuaiKuan.GeoscienceTransectfromDongUijimqinQi,Neimongol,toDonggou,Liaoning.ChineseJ.Geophys.(ActaGeophysicaSinica),1993,36(6):765—772.
[11] 刘昌铨,甲世旭.唐山地震区地壳上地幔结构特征.地震学报,1986,8(4):341—353.LIUChangQuan,JIAShiXu.StructuralpropertyofthecrustandtheuppermantleintheTangshanearthquakeregion.ActaSeismologicaSinica,1986,8(4):341—353.
[12] 辽宁省地震局编.辽宁省地震目录(公元2—1989年)、(1990—1994年).沈阳:辽宁大学出版社.1995.CompiledbyLiaoningSeismologicalBureau,Liaoningearthquakes’catalogue,(AD 2—1989),(1990—1994),Shenyang:LiaoningUniversityPress.1995.
[13] 国家地震局震害防御司编译,全球重大灾害性地震目录.北京:地震出版社,1996.EarthquakeDisasterPreventionDepartmentofChinaSeismologicalBureau.ThecatalogueofGlobalFetalcalamityearthquakes.Beijing:SeismologicalPress,1996.
[14] 卢造勋,孟补在,李 平.海城地震区地壳深部似三维空间结构特征与地震.东北地震研究,1991,7(6):1—11.LUZaoXun,MENGBuZai,LIPing.Thequasi3DtectoniccharacteristicsofthedeepcrustinHaichengSeismicregionandcorrespondingrelationshipwithEarthquake.SeismologicalResearchofNortheastChina,1991,7(6):1—11.
[15] Herrin,E .,Tucker,W .,Taggart,J.,etal.EstimationofsurfacefocusPtraveltimes.Bull.Seism.Soc,Am.,1968,58:1273—1291.
[16] 卢造勋.中国海城地震与地壳上地幔异常结构.长春地质学院学报,1992,22(4):454—459.LUZaoXun.HaichengearthquakeinChinaanditsrelationstoabnormaltectonicsofthecrustanduppermantle.JournalofChangchunGeologyCollege,1992,22(4):454—459.
[17] 雷清清,孟补在,牛 雪等.中朝地台东北缘3km深度地震层析成像的地质解释.东北地震研究,1999,15(1):37—45.LEIQingQing,MENGBuZai,NIUXue,etal.Geologicalinterpretationofseismo tomographyImage3kminnortheastedgeofSinoKoreanplatform.SeismologicalResearchofNortheastChina,1999,15(1):37—45.
[18] 姜德录,白 云,卢造勋.中朝地台东北缘及其邻区软流圈分布特征与构造运动的关系.东北地震研究,2000,16(1):14—25.JIANGDeLu,BAIYun,LUZaoXun,TheasthenospheredistributionfeaturesandtherelationtotectonicactivitiesintheareaofnortheastmarginofSinoKoreanplatformanditsneighboringarea.SeismologicalResearchofNortheastChina,2000,16(1):14—25.
[19] 卢造勋,刘国栋,位梦华等.辽南地区地壳与上地幔介质的横向不均匀性与海城7.3级地震.地震学报,1990,12(4):367—378.LUZaoXun,LIUGuoDong,WEIMengHua,etal.LateralinhomogeneityofthecrustanduppermantleinsouthLiaoning,Chinaandit’srelationshipwiththeMs=7.3Haichenearthquake.ActaSeismologicaSinica,1990,12(4):367—378.
[20] 夏怀宽,卢造勋,牛 雪等.海城、朝阳地震区的岩石圈特征.见:卢造勋等编,发展中的地震科学研究.北京:地震出版社,1995.158—164.XIAHuaiKuan,LUZaoXun,NIUXueetal.ThecharacteristicsofthelithosphereinHaichengandChaoyangseismicarea,Liaoning.In:LUZaoXunetal.ed,ProceedingsofSymposiumonEarthquakeResearch.Beijing:SeismologicalPress,1995.158—164.
[21] 卢造勋,潘 科,蒋秀琴等.胶辽渤海地区地壳上地幔结构特征与地震活动.活动断裂研究,2001,8:9—31.LUZaoXun,PANKe,JIANGXiuQin,etal.StructureChateristicsofthecrustanduppermantleandseismicityintheJiaoliaoandBohaiSeaarea.ResearchonActiveFault,2001,8:9—31.
[22] 赵俊猛,卢造勋.辽河裂谷的深部构造与裂谷活动的侧向迁移.地震地质,1998,20(3):225—233.ZHAOJunMeng,LUZaoXun.DeepstructureofLiaoheriftvalleyandeastwardmigration.Seismogeology,1998,20(3):225—233.
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