郯庐断裂带鲁苏皖段地壳速度结构的分段特征及其地质意义
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摘要
本文采用天然地震近震走时反演地壳三维速度结构的方法获得了郯庐断裂带鲁苏皖段及附近地壳(30°N—37°N,113°E—122°E)三维速度结构.对地壳内分层速度结构的分析发现,郯庐断裂带鲁苏皖段存在速度的分段特征.郯庐断裂带鲁苏皖段浅层35.3°N以北,34.5°N—35.3°N间,33°N—34.5°N间呈现的速度分段和地表出露地层有关,与地质上安丘段、莒县—郯城段,新沂—泗洪段三个破裂单元相对应,且和各段的地震活动相呼应,表明郯庐带新沂到泗洪段可能是断裂的闭锁段.郯庐断裂带鲁苏皖段地壳速度结构自浅至深分为三段,大体位置是:南段(32.5°N—33°N以南),中段(32.5°N—33°N至35°N—35.3°N),北段(35°N—35.3°N以北).上地壳分段与苏鲁超高压变质岩带的插入有关,中、下地壳速度分段则可能和火山岩滞留有关.地壳各层速度结构不同段的速度差异反映了构造块体的速度差异,表明各构造块体在地壳下部仍有差异,郯庐带西侧速度总体高于东侧,反映了不同构造块体的形成和组成差别,也说明了该断裂带可能延伸到莫霍面.而不同深度的分段性可能反映了不同地质演化过程.
The Yishu segment of the Tanlu fault zone is the seismogenic structure of the 1668 Tangchen M81/2earthquake,where is the research focus of the potential strong earthquake location in the future.Geological survey shows different activity degrees along the ShandongJiangsu-Anhui segment of the Tanlu fault zone,but few researches focus on the crustal velocity structure beneath this area,and the relationship of seismicity and the difference of crustal velocity structure.The 3Dvelocity structure beneath this segment of the Tanlu fault zone and adjacent areas(30°N—37°N,113°E—122°E)was imaged by seismic tomography.Crustal velocity structuresegmentation beneath the researched area,its characters and relationship with the geological structure segmentations,and seismic levels are studied in this paper.We select the earthquakes occurred from 1980 to 2011in the research area,and relocate these events through a relative relocation technique.Based on the travel-time data of Pg,Sg,Pm,Sm,Pn,Sn,pP,and sS waves of these earthquakes,using the multi-phase travel-time inversion method,the 3Dvelocity structure(inversion grid is 30km×30km)beneath the research area is imaged by seismic tomography.The analysis of the velocity distribution patterns of different depths for the research area suggests that the crustal velocity structure has segmentation.For shallow layers,different velocity segments,north of 35.3°N,34.5°N—35.3°N,and 33°N—34.5°N,are related to exposed strata,respectively corresponding to three rupture elements of the Tanlu fault zone.They are Anqiu segment,Ju county-Tancheng segment,and Xinyi-Sihong segment,which have different earthquake activity patterns.It indicates the Xinyi-Sihong segment is the blocked segment of the Tanlu fault.The crustal velocity structure beneath the Shandong-Jiangsu-Anhui segment of the Tanlu fault zone and adjacent areas can be roughly divided into three different segments from top to bottom.They include the south segment(south of 32.5°N—33°N),middle segment(between32.5°N—33°N to 35°N—35.3°N)and north segment(north of 35°N—35.3°N.The segmentation of upper crust is related to insertion from the Su-Lu UHPM belt,the segmentation of middle and lower crust is related to detention of volcanics.The velocities in the west of the Tanlu fault zone is higher than that in the east.The differences of velocity distribution patterns at different depths show different tectonic blocks,which have different evolution histories and compositions,also meaning that this fault extends down to the Moho.Different velocity segments at different depths beneath the Shandong-Jiangsu-Anhui segment of the Tanlu fault zone are related to geology factors such as exposed strata,rupture units of the fault zone,Su-Lu UHPM belt,detention of volcanics or different tectonic blocks.Through analysis of the seismic activity of the different rupture umits of the Tanlu fault zone in the researched area,the consistency of velocity segments and rupture units indicate the Xinyi-Sihong segment is the blocked segment of the Tanlu fault zone,where strong earthquakes may occure in the future.
The Yishu segment of the Tanlu fault zone is the seismogenic structure of the 1668 Tangchen M81/2earthquake,where is the research focus of the potential strong earthquake location in the future.Geological survey shows different activity degrees along the ShandongJiangsu-Anhui segment of the Tanlu fault zone,but few researches focus on the crustal velocity structure beneath this area,and the relationship of seismicity and the difference of crustal velocity structure.The 3Dvelocity structure beneath this segment of the Tanlu fault zone and adjacent areas(30°N—37°N,113°E—122°E)was imaged by seismic tomography.Crustal velocity structuresegmentation beneath the researched area,its characters and relationship with the geological structure segmentations,and seismic levels are studied in this paper.We select the earthquakes occurred from 1980 to 2011in the research area,and relocate these events through a relative relocation technique.Based on the travel-time data of Pg,Sg,Pm,Sm,Pn,Sn,pP,and sS waves of these earthquakes,using the multi-phase travel-time inversion method,the 3Dvelocity structure(inversion grid is 30km×30km)beneath the research area is imaged by seismic tomography.The analysis of the velocity distribution patterns of different depths for the research area suggests that the crustal velocity structure has segmentation.For shallow layers,different velocity segments,north of 35.3°N,34.5°N—35.3°N,and 33°N—34.5°N,are related to exposed strata,respectively corresponding to three rupture elements of the Tanlu fault zone.They are Anqiu segment,Ju county-Tancheng segment,and Xinyi-Sihong segment,which have different earthquake activity patterns.It indicates the Xinyi-Sihong segment is the blocked segment of the Tanlu fault.The crustal velocity structure beneath the Shandong-Jiangsu-Anhui segment of the Tanlu fault zone and adjacent areas can be roughly divided into three different segments from top to bottom.They include the south segment(south of 32.5°N—33°N),middle segment(between32.5°N—33°N to 35°N—35.3°N)and north segment(north of 35°N—35.3°N.The segmentation of upper crust is related to insertion from the Su-Lu UHPM belt,the segmentation of middle and lower crust is related to detention of volcanics.The velocities in the west of the Tanlu fault zone is higher than that in the east.The differences of velocity distribution patterns at different depths show different tectonic blocks,which have different evolution histories and compositions,also meaning that this fault extends down to the Moho.Different velocity segments at different depths beneath the Shandong-Jiangsu-Anhui segment of the Tanlu fault zone are related to geology factors such as exposed strata,rupture units of the fault zone,Su-Lu UHPM belt,detention of volcanics or different tectonic blocks.Through analysis of the seismic activity of the different rupture umits of the Tanlu fault zone in the researched area,the consistency of velocity segments and rupture units indicate the Xinyi-Sihong segment is the blocked segment of the Tanlu fault zone,where strong earthquakes may occure in the future.
引文
Chao H T,Li J L,Cui Z W,et al.1997.Mode of motion of the Holocene fault in Weifang-Jiashan segment of the Tanlu Fault Zone and earthquake-generating model.Journal of Seismological Research(in Chinese),20(2):218-226.
Gao E G,Xu G M.1996.A new kind of step by step iterative raytracing method.Acta Geophysica Sinica(in Chinese),39(supplement):302-308.
Geoscience Transect Research Group of CSB.1991.Explanatory Notes of the Geosciences Transect of Jiangsu Xiangshui-Nei mengol Mandula(in Chinese).Beijing:Seismological Press.
Geoscience Transect Research Group of CSB.1992.Explanatory Notes of the Geosciences Transect of Shanghai Fengxian-Nei mongol Alxa(in Chinese).Beijing:Seismological Press.
Hao T Y,Suh M,Liu J H,et al.2004.Deep structure and boundary belt position between Sino-Korean and Yangtze blocks in Yellow Sea.Earth Science Frontiers(in Chinese),11(3):51-61.
Huang Y,Li Q H,Zhang Y S,et al.2008.Relocation of earthquakes in Jiangsu and neighboring areas,China and analysis of structural features.Chinese J.Geophys.(in Chinese),51(1):175-185.
Huang Y,Li Q H,Zhang Y S,et a1.2011.Crustal velocity structure beneath the Shandong-Jiangsu-Anhui segment of the Tancheng-Lujiang Fault Zone and adjacent areas.Chinese J.Geophys.(in Chinese),54(10):2549-2559,doi:10.3969/j.issn.0001-5733.2011.10.012.
Koch M.1993.Simultaneous inversion for 3-D crustal structure and hypocentres including direct,refracted and reflected phases-Ⅰ.Development,validation and optimal regularization of the method.Geophys.J.Int.,112(3):385-412.
Li C F,Chen B,Zhou Z Y.2009.Deep crustal structures of eastern China and adjacent seas revealed by magnetic data.Science in China Series D:Earth Sciences,52(7):984-993.
Li J L,Chao H T,Cui Z W,et al.1994.Segmentation of active fault along the Tancheng-Lujiang Fault Zone and evaluation of strong earthquake risk.Seismology and Geology(in Chinese),16(2):121-126.
Li Q H,Zhang Y S,Bao H Y,et al.2014.Crust velocity structure inference of the epicenter of the M81/2earthquake at Tancheng,Shandong,China,in 1668.Earthquake Research in China(in Chinese),28(3):320-334.
Li Q H,Zhang Y S,Kim S G.2007.3-D crustal velocity tomography in the southern Korean Peninsula.ChineseJ.Geophys.(in Chinese),50(4):1073-1081.
Li Z W,Xu Y,Hao T Y,et al.2006.Seismic tomography and velocity structure in the crust and upper mantle around Bohai Sea area.Chinese J.Geophys.(in Chinese),49(3):797-804.
Ling C,Tian Y Z,Wei W X.2006.A thinned lithospheric image of the Tanlu Fault Zone,eastern China:Constructed from wave equation based receiver function migration.J.Geophys.Res.,111(B9),doi:10.1029/2005JB003974.
Liu C Q,Zhu Z P,Li H D,et al.1983.Lianyungang-Linyi-Sishui deep seismic sounding profile and deep tectonic background of Linyi M8.5earthquake.Earthquake(in Chinese),(3):11-17.
Liu J H,Liu F T,Sun R M,et al.1995.Seismic tomography beneath the Qinling-Dabie organic belts and both the northern and southern fringes.Acta Geophysica Sinica(in Chinese),38(1):46-54.
Sambridge M,Drijkoningen G.1992.Genetic algorithms in seismic waveform inversion.Geophys.J.Int.,109(2):323-342.
Wang L S,Li C,Shi Y S,et al.1995.Distributions of geotemperature and terrestrial heat flow density in lower Yangtze area.Acta Geophysica Sinica(in Chinese),38(4):469-476.
Xiao X B,Zhao G Z,Wang J J,et al.2008.Research on the deep electric structure of Sulu orogenic belt and adjacent area.Science in China(Series D)(in Chinese),38(10):1258-1267.
Xu P F,Liu F T,Wang Q C,et al.2000.Seismic tomography beneath the Dabie-Sulu collision orogen-3-D velocity structures of lithosphere.Chinese J.Geophys.(in Chinese),43(3):377-385.
Yang W C,Cheng Z Y,Chen G J,et al.1999a.Geophysical investigations in northern Sulu UHPM belt,Part I:deep seismic reflection.Chinese J.Geophys.(in Chinese),42(1):41-52.
Yang W C,Hu Z Y,Cheng G Y,et al.1999b.Long profile of geophysical investigation from Tanchen to Lianshui,eastcentral China.Chinese J.Geophys.(in Chinese),42(2):206-217.
Zhang J H,Zhao G Z,Xiao X B,et al.2010.Analysis of electric structure of the central Tan-Lu fault zone(Yi-Shu fault zone,36°N)and seismogenic condition.Chinese J.Geophys.(in Chinese),53(3):605-611,doi:10.3969/j.issn.0001-5733.2010.03.014.
Zhang Y S,Li Q H,Liu Y W,et al.2003.The seismic tomography software.Northwestern Seismological Journal(in Chinese),25(2):170-174.
Zhang Y S,Li Q H,Xu G M.1998.Combined inversion technique to study 3-D crustal velocity structure by using seismic wave travel time and wave form(I)-theory and method.Northwestern Seismological Journal(in Chinese),20(2):8-15.
Zhang Y S,Zhou M D,Rong D L,et al.2004.3-D Velocity structure in the central-eastern part of Qilian Shan.Acta Seismologica Sinica(in Chinese),26(3):247-255.
晁洪太,李家灵,崔昭文等.1997.郯庐断裂带潍坊-嘉山段全新世活断层的活动方式与发震模式.地震研究,20(2):218-226.
高尔根,徐果明.1996.二维速度随机分布逐步迭代射线追踪方法.地球物理学报,39(增刊):302-308.
国家地震局地学断面编委会.1991.江苏响水至内蒙古满都拉地学剖面说明书.北京:地质出版社.
国家地震局地学断面编委会.1992.上海奉贤至内蒙古阿拉善左旗地学断面说明书.北京:地震出版社.
郝天珧,Suh M,刘建华等.2004.黄海深部结构与中朝-扬子块体结合带在海区位置的地球物理研究.地学前缘,11(3):51-61.
黄耘,李清河,张元生等.2008.江苏及邻区地震重新定位和构造特征分析.地球物理学报,51(1):175-185.
黄耘,李清河,张元生等.2011.郯庐断裂带鲁苏皖段及邻区地壳速度结构.地球物理学报,54(10):2549-2559,doi:10.3969/j.issn.0001-5733.2011.10.012.
李春峰,陈冰,周祖翼.2009.中国东部及邻近海域磁异常数据所揭示的深部构造.中国科学D辑:地球科学,39(12):1770-1779.
李家灵,晁洪太,崔昭文等.1994.郯庐活断层的分段及其大震危险性分析.地震地质,16(2):121-126.
李清河,张元生,鲍海英等.2014.据地壳速度结构推测1668年山东郯城81/2级大地震震中.中国地震,30(1):30-42.
李清河,张元生,Kim S G.2007.朝鲜半岛南部三维地壳速度结构成像.地球物理学报,50(4):1073-1081.
李志伟,胥颐,郝天珧等.2006.环渤海地区的地震层析成像与地壳上地幔结构.地球物理学报,49(3):797-804.
刘昌铨,祝治平,李捍东等.1983.连云港-临沂-泗水测深剖面及临沂8.5级地震深部构造背景.地震,(3):11-17.
刘建华,刘福田,孙若昧等.1995.秦岭-大别造山带及其南北缘地震层析成像.地球物理学报,38(1):46-54.
王良书,李成,施央申等.1995.下扬子区地温场和大地热流密度分布.地球物理学报,38(4):469-476.
肖骑彬,赵国泽,王继军等.2008.苏鲁造山带及邻区深部电性结构研究.中国科学D辑:地球科学,38(10):1258-1267.
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杨文采,程振炎,陈国九等.1999a.苏鲁超高压变质带北部地球物理调查(1)-深反射地震.地球物理学报,42(1):41-52.
杨文采,胡振远,程振炎等.1999b.郯城-涟水综合地球物理剖面.地球物理学报,42(2):206-217.
张继红,赵国泽,肖骑彬等.2010.郯庐断裂带中段(沂沭断裂带)电性结构研究与孕震环境.地球物理学报,53(3):605-611,doi:10.3969/j.issn.0001-5733.2010.03.014.
张元生,李清河,刘耀炜等.2003.地震层析成像软件.西北地震学报,25(2):170-174.
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张元生,周民都,荣代潞等.2004.祁连山中东段地区三维速度结构研究.地震学报,26(3):247-255.
Gao E G,Xu G M.1996.A new kind of step by step iterative raytracing method.Acta Geophysica Sinica(in Chinese),39(supplement):302-308.
Geoscience Transect Research Group of CSB.1991.Explanatory Notes of the Geosciences Transect of Jiangsu Xiangshui-Nei mengol Mandula(in Chinese).Beijing:Seismological Press.
Geoscience Transect Research Group of CSB.1992.Explanatory Notes of the Geosciences Transect of Shanghai Fengxian-Nei mongol Alxa(in Chinese).Beijing:Seismological Press.
Hao T Y,Suh M,Liu J H,et al.2004.Deep structure and boundary belt position between Sino-Korean and Yangtze blocks in Yellow Sea.Earth Science Frontiers(in Chinese),11(3):51-61.
Huang Y,Li Q H,Zhang Y S,et al.2008.Relocation of earthquakes in Jiangsu and neighboring areas,China and analysis of structural features.Chinese J.Geophys.(in Chinese),51(1):175-185.
Huang Y,Li Q H,Zhang Y S,et a1.2011.Crustal velocity structure beneath the Shandong-Jiangsu-Anhui segment of the Tancheng-Lujiang Fault Zone and adjacent areas.Chinese J.Geophys.(in Chinese),54(10):2549-2559,doi:10.3969/j.issn.0001-5733.2011.10.012.
Koch M.1993.Simultaneous inversion for 3-D crustal structure and hypocentres including direct,refracted and reflected phases-Ⅰ.Development,validation and optimal regularization of the method.Geophys.J.Int.,112(3):385-412.
Li C F,Chen B,Zhou Z Y.2009.Deep crustal structures of eastern China and adjacent seas revealed by magnetic data.Science in China Series D:Earth Sciences,52(7):984-993.
Li J L,Chao H T,Cui Z W,et al.1994.Segmentation of active fault along the Tancheng-Lujiang Fault Zone and evaluation of strong earthquake risk.Seismology and Geology(in Chinese),16(2):121-126.
Li Q H,Zhang Y S,Bao H Y,et al.2014.Crust velocity structure inference of the epicenter of the M81/2earthquake at Tancheng,Shandong,China,in 1668.Earthquake Research in China(in Chinese),28(3):320-334.
Li Q H,Zhang Y S,Kim S G.2007.3-D crustal velocity tomography in the southern Korean Peninsula.ChineseJ.Geophys.(in Chinese),50(4):1073-1081.
Li Z W,Xu Y,Hao T Y,et al.2006.Seismic tomography and velocity structure in the crust and upper mantle around Bohai Sea area.Chinese J.Geophys.(in Chinese),49(3):797-804.
Ling C,Tian Y Z,Wei W X.2006.A thinned lithospheric image of the Tanlu Fault Zone,eastern China:Constructed from wave equation based receiver function migration.J.Geophys.Res.,111(B9),doi:10.1029/2005JB003974.
Liu C Q,Zhu Z P,Li H D,et al.1983.Lianyungang-Linyi-Sishui deep seismic sounding profile and deep tectonic background of Linyi M8.5earthquake.Earthquake(in Chinese),(3):11-17.
Liu J H,Liu F T,Sun R M,et al.1995.Seismic tomography beneath the Qinling-Dabie organic belts and both the northern and southern fringes.Acta Geophysica Sinica(in Chinese),38(1):46-54.
Sambridge M,Drijkoningen G.1992.Genetic algorithms in seismic waveform inversion.Geophys.J.Int.,109(2):323-342.
Wang L S,Li C,Shi Y S,et al.1995.Distributions of geotemperature and terrestrial heat flow density in lower Yangtze area.Acta Geophysica Sinica(in Chinese),38(4):469-476.
Xiao X B,Zhao G Z,Wang J J,et al.2008.Research on the deep electric structure of Sulu orogenic belt and adjacent area.Science in China(Series D)(in Chinese),38(10):1258-1267.
Xu P F,Liu F T,Wang Q C,et al.2000.Seismic tomography beneath the Dabie-Sulu collision orogen-3-D velocity structures of lithosphere.Chinese J.Geophys.(in Chinese),43(3):377-385.
Yang W C,Cheng Z Y,Chen G J,et al.1999a.Geophysical investigations in northern Sulu UHPM belt,Part I:deep seismic reflection.Chinese J.Geophys.(in Chinese),42(1):41-52.
Yang W C,Hu Z Y,Cheng G Y,et al.1999b.Long profile of geophysical investigation from Tanchen to Lianshui,eastcentral China.Chinese J.Geophys.(in Chinese),42(2):206-217.
Zhang J H,Zhao G Z,Xiao X B,et al.2010.Analysis of electric structure of the central Tan-Lu fault zone(Yi-Shu fault zone,36°N)and seismogenic condition.Chinese J.Geophys.(in Chinese),53(3):605-611,doi:10.3969/j.issn.0001-5733.2010.03.014.
Zhang Y S,Li Q H,Liu Y W,et al.2003.The seismic tomography software.Northwestern Seismological Journal(in Chinese),25(2):170-174.
Zhang Y S,Li Q H,Xu G M.1998.Combined inversion technique to study 3-D crustal velocity structure by using seismic wave travel time and wave form(I)-theory and method.Northwestern Seismological Journal(in Chinese),20(2):8-15.
Zhang Y S,Zhou M D,Rong D L,et al.2004.3-D Velocity structure in the central-eastern part of Qilian Shan.Acta Seismologica Sinica(in Chinese),26(3):247-255.
晁洪太,李家灵,崔昭文等.1997.郯庐断裂带潍坊-嘉山段全新世活断层的活动方式与发震模式.地震研究,20(2):218-226.
高尔根,徐果明.1996.二维速度随机分布逐步迭代射线追踪方法.地球物理学报,39(增刊):302-308.
国家地震局地学断面编委会.1991.江苏响水至内蒙古满都拉地学剖面说明书.北京:地质出版社.
国家地震局地学断面编委会.1992.上海奉贤至内蒙古阿拉善左旗地学断面说明书.北京:地震出版社.
郝天珧,Suh M,刘建华等.2004.黄海深部结构与中朝-扬子块体结合带在海区位置的地球物理研究.地学前缘,11(3):51-61.
黄耘,李清河,张元生等.2008.江苏及邻区地震重新定位和构造特征分析.地球物理学报,51(1):175-185.
黄耘,李清河,张元生等.2011.郯庐断裂带鲁苏皖段及邻区地壳速度结构.地球物理学报,54(10):2549-2559,doi:10.3969/j.issn.0001-5733.2011.10.012.
李春峰,陈冰,周祖翼.2009.中国东部及邻近海域磁异常数据所揭示的深部构造.中国科学D辑:地球科学,39(12):1770-1779.
李家灵,晁洪太,崔昭文等.1994.郯庐活断层的分段及其大震危险性分析.地震地质,16(2):121-126.
李清河,张元生,鲍海英等.2014.据地壳速度结构推测1668年山东郯城81/2级大地震震中.中国地震,30(1):30-42.
李清河,张元生,Kim S G.2007.朝鲜半岛南部三维地壳速度结构成像.地球物理学报,50(4):1073-1081.
李志伟,胥颐,郝天珧等.2006.环渤海地区的地震层析成像与地壳上地幔结构.地球物理学报,49(3):797-804.
刘昌铨,祝治平,李捍东等.1983.连云港-临沂-泗水测深剖面及临沂8.5级地震深部构造背景.地震,(3):11-17.
刘建华,刘福田,孙若昧等.1995.秦岭-大别造山带及其南北缘地震层析成像.地球物理学报,38(1):46-54.
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