西宁市活断层地震构造模型初步研究
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摘要
在西宁市城市活断层探测的基础上,对城市活断层与地层褶皱变形的关系进行了研究,认为湟水河断层和NW向的湟水河北岸断层为背斜顶部张性断层,南川河断层为褶皱不均匀变形形成的横向撕裂断层,北川河东岸断层为向斜核部或翼部发育的挤压断层。并根据褶皱变形平衡剖面和重力资料反演,推测了褶皱变形滑脱面深度,初步建立了西宁市城市活断层的地震构造模型。依据地震构造模型,对城市活断层的发震能力进行了讨论。
The Xining basin is a Cenozoic basin bounded by the Riyueshan Fault and the Lajishan Fault on the south,the Dabanshan Fault on the north.Controlled by these active boundary faults and under the near NE-oriented compressional stress,fold deformation occurred inside the basin.Several active faults of NE or EW trending were detected.Nevertheless,all of them are small and weakly active.By the study on the relationship between fault and folding,we think that the Huangshuihe Fault and the NW-strike north bank of Huangshuihe Fault are tensional faults developed on the apex of an anticline;the Nanchuanhe Fault is a transverse tear fault resulting from differential folding on the two sides of the fault;and the east bank of Beichuanhe Fault is a compressional fault developed on the core or limb of an syncline.By the balanced cross-section analysis of fold deformation and inversion of gravity anomaly data,we obtained that the depth of detachment plane is about 4～5km.Thus,based on the above data,the seismotectonic model of the Xining urban area is built.We conclude that the faults of the area are the secondary faults related to folding of overburdens and have no potential of producing earthquakes larger than magnitude 6 for their small scale and shallow depth.
The Xining basin is a Cenozoic basin bounded by the Riyueshan Fault and the Lajishan Fault on the south,the Dabanshan Fault on the north.Controlled by these active boundary faults and under the near NE-oriented compressional stress,fold deformation occurred inside the basin.Several active faults of NE or EW trending were detected.Nevertheless,all of them are small and weakly active.By the study on the relationship between fault and folding,we think that the Huangshuihe Fault and the NW-strike north bank of Huangshuihe Fault are tensional faults developed on the apex of an anticline;the Nanchuanhe Fault is a transverse tear fault resulting from differential folding on the two sides of the fault;and the east bank of Beichuanhe Fault is a compressional fault developed on the core or limb of an syncline.By the balanced cross-section analysis of fold deformation and inversion of gravity anomaly data,we obtained that the depth of detachment plane is about 4～5km.Thus,based on the above data,the seismotectonic model of the Xining urban area is built.We conclude that the faults of the area are the secondary faults related to folding of overburdens and have no potential of producing earthquakes larger than magnitude 6 for their small scale and shallow depth.
引文
[1]青海省地震局,1996,湟水(西宁)盆地活动构造调查及地壳稳定性研究。
[1]青海省地质矿产勘查开发局,2003,青海省1/100万布格重力异常等值线图、青海省1/100万剩余重力异常等值线图。
丁国瑜,田勤俭,孔凡臣,等.1993.活断层分段:原则、方法与应用[M].北京:地震出版社.DING Guo-yu,TIAN Qin-jian,KONG Fan-chen,et al.1993.Segmentation of Active Fault[M].SeismologicalPress,Beijing(in Chinese).
国家地震局震害防御司编.1995.中国历史强震目录(公元前23世纪—公元1911年)[Z].北京:地震出版社.Earthquake Disaster Prevention Department of the State Seismological Bureau(ed).1995.Catalogue of Chinese His-torical Strong Earthquakes(23BC—1911AD)[Z].Seismological press,Beijing(in Chinese).
中国地震局震害防御司编.1999.中国近代地震目录(公元1912年—1990年MS≥4.7)[Z].北京:中国科学技术出版社.Earthquake Disaster Prevention Department of the State Seismological Bureau(ed).1999.Catalogue of Chinese Pres-ent Earthquakes(1912—1990,MS≥4.7)[Z].University of Science and Technology of China Press,Beijing(inChinese).
李智敏,田勤俭,高占武,等.2005.西宁城市活动断裂地表特征初步研究[J].地震,25(4):119—126.LI Zhi-min,TIAN Qin-jian,GAO Zhan-wu,et al.2005.Study of surficial features of the active faults in Xining City[J].Earthquake,25(4):119—126(in Chinese).
李智敏,田勤俭,姚生海,等.2007.大通断裂活动性研究[J].地震地质(待刊).LI Zhi-min,TIAN Qin-jian,YAO Sheng-hai,et al.2007.Study for Datong Fault belt[J].Seismology and Geology(in press)(in Chinese).
田勤俭,丁国瑜,申旭辉.2002.青藏高原东北隅强震构造模型[J].地震,22(1):9—16.TIAN Qin-jian,DING Guo-yu,SHEN Xu-hui.2002.Seismic tectonic model of the northeastern corner of the TibetPlateau[J].Earthquake,22(1):9—16(in Chinese).
[1]中国地震局分析预报中心,2001,中国近代(1970—2000年)地震目录。
王运所,刘亚洲,张孝义,等.2003.平衡剖面的制作流程及其地质意义[J].长安大学学报(地球科学版),25(1):28—32.WANG Yun-suo,LIUYa-zhou,ZHANG Xiao-yi,et al.2003.Flowdiagram and the geological significance of balancesection[J].Journal of Chang an University(Earth Science Edition),25(1):28—32(in Chinese).
闻学泽.1998.时间相依的活动断裂分段地震危险性评估及其问题[J].科学通报,43(14):1457—1466.WEN Xue-ze.1998.Assessment of time-dependent seismic hazards on segments of active fault,and its problems[J].Chinese Science Bulletin,43(23):1937—1950.
闻学泽.2001.活动断裂的分段地震震级评估[A].见:中国地震局地质研究所编.活动断裂研究(8).北京:地震出版社.32—40.WEN Xue-ze.2001.Assessing magnitudes of segment-rupturing earthquakes on active faults[A].In:Institute of Geolo-gy,CSB(ed).Research on Active Fault(8).Seismological Press,Beijing.32—40(in Chinese).
薛冈,卢华复,朱成宏,等.2001.伸展区域平衡剖面法及其在构造分析中的应用[J].高校地质学报,7(4):427—434.XUE Gang,LU Hua-fu,ZHU Cheng-hong,et al.2001.Structure Restoration of Balancing Cross Section in ExtensionArea:An Example from the Huaifu Depression,North Jiangsu Basin[J].Geological Journa1of China Universities,7(4):427—434(in Chinese).
岳华,张洪波,李仁甫,等.2002.Geosec平衡剖面技术在M盆地构造研究中的应用[J].勘探地球物理进展,25(4):49—52.YUE Hua,ZHANG Hong-bo,LI Ren-fu,et al.2002.Application of Geosec in the structure studies of M Basin[J].Progress in Exploration Geophysics,25(4):49—52(in Chinese).
袁道阳,刘小龙,张培震,等.2003.青海热水?日月山断裂带的新活动特征[J].地震地质,25(1):155—165.YUAN Dao-yang,LIUXiao-long,ZHANG Pei-zhen,et al.2003.Characteristics of the modern activity of the Reshui-Riyueshan Fault zone in Qinghai Province[J].Seismology and Geology,25(1):155—165(in Chinese).
袁道阳,张培震,雷中生,等.2005.青海拉脊山断裂带新活动特征的初步研究[J].中国地震,21(1):93—102.YUAN Dao-yang,ZHANG Pei-zhen,LEI Zhong-sheng,et al.2005.A preliminary study on the new activity featuresof the Laji Mountain Fault zone in Qinghai Province[J].Earthquake Research in China,21(1):93—102(inChinese).
杨晓平,周本刚,李军.2001.新疆南天山亚肯背斜晚更新世以来的隆起和缩短[J].地震地质,23(4):501—509.YANG Xiao-ping,ZHOUBen-gang,LI Jun.2001.Shortening and uplift of the active Yaken anticline,Southern Tian-shan,China since late Pleistocene[J].Seismology and Geology,23(4):501—509(in Chinese).
Avouac J P,Tapponnier P.1993.Kinematic model of active deformation in central Asia[J].Geophysical ResearchLetters,20:895—898.
Dahlstrom C D A.1969.Balanced cross sections[J].Canadian Journal of Earth Science,6:743—757.
Dahlstrom C D A.1970.Structural geology in the eastern margin of the Canadian Rocky Mountains[J].Bulletin ofCanadian Petroleum Geology,18:332—406.
Gibbs A D.1984.Structural evolution of extensional basin margins[J].J Geol Soc Lond,141:609—620.
Hossack J R.1979.The use of balanced cross-sections in the calculation of orogenic contraction:Areview[J].Journalof the Geological Society of London,136:705—711.
Julivert M,Arboleya M L.1986.Areal balancing and estimate of areal reduction in a thin-skinned fold-and-thrust belt(Cantabrian zone,NW Spain):Constraints on its emplacement mechanism[J].Journal of Structural Geology,8(3—4):407—414.
Woodward N B,Boyer S E,Suppe E J.1989.Balanced Geological Cross-sections-An Essential Technique in GeologicalResearch and Exploration:Short Course in Geology[M].American Geophysical Union,pp132.
[1]青海省地质矿产勘查开发局,2003,青海省1/100万布格重力异常等值线图、青海省1/100万剩余重力异常等值线图。
丁国瑜,田勤俭,孔凡臣,等.1993.活断层分段:原则、方法与应用[M].北京:地震出版社.DING Guo-yu,TIAN Qin-jian,KONG Fan-chen,et al.1993.Segmentation of Active Fault[M].SeismologicalPress,Beijing(in Chinese).
国家地震局震害防御司编.1995.中国历史强震目录(公元前23世纪—公元1911年)[Z].北京:地震出版社.Earthquake Disaster Prevention Department of the State Seismological Bureau(ed).1995.Catalogue of Chinese His-torical Strong Earthquakes(23BC—1911AD)[Z].Seismological press,Beijing(in Chinese).
中国地震局震害防御司编.1999.中国近代地震目录(公元1912年—1990年MS≥4.7)[Z].北京:中国科学技术出版社.Earthquake Disaster Prevention Department of the State Seismological Bureau(ed).1999.Catalogue of Chinese Pres-ent Earthquakes(1912—1990,MS≥4.7)[Z].University of Science and Technology of China Press,Beijing(inChinese).
李智敏,田勤俭,高占武,等.2005.西宁城市活动断裂地表特征初步研究[J].地震,25(4):119—126.LI Zhi-min,TIAN Qin-jian,GAO Zhan-wu,et al.2005.Study of surficial features of the active faults in Xining City[J].Earthquake,25(4):119—126(in Chinese).
李智敏,田勤俭,姚生海,等.2007.大通断裂活动性研究[J].地震地质(待刊).LI Zhi-min,TIAN Qin-jian,YAO Sheng-hai,et al.2007.Study for Datong Fault belt[J].Seismology and Geology(in press)(in Chinese).
田勤俭,丁国瑜,申旭辉.2002.青藏高原东北隅强震构造模型[J].地震,22(1):9—16.TIAN Qin-jian,DING Guo-yu,SHEN Xu-hui.2002.Seismic tectonic model of the northeastern corner of the TibetPlateau[J].Earthquake,22(1):9—16(in Chinese).
[1]中国地震局分析预报中心,2001,中国近代(1970—2000年)地震目录。
王运所,刘亚洲,张孝义,等.2003.平衡剖面的制作流程及其地质意义[J].长安大学学报(地球科学版),25(1):28—32.WANG Yun-suo,LIUYa-zhou,ZHANG Xiao-yi,et al.2003.Flowdiagram and the geological significance of balancesection[J].Journal of Chang an University(Earth Science Edition),25(1):28—32(in Chinese).
闻学泽.1998.时间相依的活动断裂分段地震危险性评估及其问题[J].科学通报,43(14):1457—1466.WEN Xue-ze.1998.Assessment of time-dependent seismic hazards on segments of active fault,and its problems[J].Chinese Science Bulletin,43(23):1937—1950.
闻学泽.2001.活动断裂的分段地震震级评估[A].见:中国地震局地质研究所编.活动断裂研究(8).北京:地震出版社.32—40.WEN Xue-ze.2001.Assessing magnitudes of segment-rupturing earthquakes on active faults[A].In:Institute of Geolo-gy,CSB(ed).Research on Active Fault(8).Seismological Press,Beijing.32—40(in Chinese).
薛冈,卢华复,朱成宏,等.2001.伸展区域平衡剖面法及其在构造分析中的应用[J].高校地质学报,7(4):427—434.XUE Gang,LU Hua-fu,ZHU Cheng-hong,et al.2001.Structure Restoration of Balancing Cross Section in ExtensionArea:An Example from the Huaifu Depression,North Jiangsu Basin[J].Geological Journa1of China Universities,7(4):427—434(in Chinese).
岳华,张洪波,李仁甫,等.2002.Geosec平衡剖面技术在M盆地构造研究中的应用[J].勘探地球物理进展,25(4):49—52.YUE Hua,ZHANG Hong-bo,LI Ren-fu,et al.2002.Application of Geosec in the structure studies of M Basin[J].Progress in Exploration Geophysics,25(4):49—52(in Chinese).
袁道阳,刘小龙,张培震,等.2003.青海热水?日月山断裂带的新活动特征[J].地震地质,25(1):155—165.YUAN Dao-yang,LIUXiao-long,ZHANG Pei-zhen,et al.2003.Characteristics of the modern activity of the Reshui-Riyueshan Fault zone in Qinghai Province[J].Seismology and Geology,25(1):155—165(in Chinese).
袁道阳,张培震,雷中生,等.2005.青海拉脊山断裂带新活动特征的初步研究[J].中国地震,21(1):93—102.YUAN Dao-yang,ZHANG Pei-zhen,LEI Zhong-sheng,et al.2005.A preliminary study on the new activity featuresof the Laji Mountain Fault zone in Qinghai Province[J].Earthquake Research in China,21(1):93—102(inChinese).
杨晓平,周本刚,李军.2001.新疆南天山亚肯背斜晚更新世以来的隆起和缩短[J].地震地质,23(4):501—509.YANG Xiao-ping,ZHOUBen-gang,LI Jun.2001.Shortening and uplift of the active Yaken anticline,Southern Tian-shan,China since late Pleistocene[J].Seismology and Geology,23(4):501—509(in Chinese).
Avouac J P,Tapponnier P.1993.Kinematic model of active deformation in central Asia[J].Geophysical ResearchLetters,20:895—898.
Dahlstrom C D A.1969.Balanced cross sections[J].Canadian Journal of Earth Science,6:743—757.
Dahlstrom C D A.1970.Structural geology in the eastern margin of the Canadian Rocky Mountains[J].Bulletin ofCanadian Petroleum Geology,18:332—406.
Gibbs A D.1984.Structural evolution of extensional basin margins[J].J Geol Soc Lond,141:609—620.
Hossack J R.1979.The use of balanced cross-sections in the calculation of orogenic contraction:Areview[J].Journalof the Geological Society of London,136:705—711.
Julivert M,Arboleya M L.1986.Areal balancing and estimate of areal reduction in a thin-skinned fold-and-thrust belt(Cantabrian zone,NW Spain):Constraints on its emplacement mechanism[J].Journal of Structural Geology,8(3—4):407—414.
Woodward N B,Boyer S E,Suppe E J.1989.Balanced Geological Cross-sections-An Essential Technique in GeologicalResearch and Exploration:Short Course in Geology[M].American Geophysical Union,pp132.
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