中国强震发生带地震构造的几点思考
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摘要
强震发生带是指全新世 (约 1.2万年 )以来发生过和将来还会发生M≥ 6级地震的地带。中国强震发生带的动力源主要来自印度板块向NNE的顶撞作用 ,而太平洋板块向西俯冲则次之。板块、断块及锒嵌其间的缝合线、深大断裂带 ,组成了窗棂结构 ,受力时“窗棂”(缝合线、深大断裂 )发生错动 ,而“窗”(板块、断块 )的内部则相对稳定。第四纪以来 ,以我国西南鲜水河———小江断裂带为例 ,在Q1、Q2 时期因断裂带作左旋扭动 ,在拉张区形成许多断陷盆地 ;到Q3由于地应力方向改变 ,运动加剧 ,使不同方向断裂互相贯通 ,活动延续至今 ,称之为活动断裂带。强震多发生在活动断裂带的特殊部位 ,震中区地面强烈变形 ,表现为毗邻地段猛烈升降、地堑地垒系和断头河等。由古地震研究得知Q4 以来强震常在原地多次重复 ,且震级相近。由台湾 1999年集集地震和云南195 5年鱼地震的加速度等值线和等烈度线图形对比 ,建筑物破坏程度和昔格达层变形对照 ,得出强震构造变形机理乃系“夹心饼干”似的三层结构所致 ,三层即是断层的二盘和其所夹持的断层破碎带 ,后者是地应力聚集和释放的场所 ,是地震波的良好通道
The term strong earthquake occuring sections (SEOS) is used to specify those places where strong earthquakes (M≥6) have occurred since Holocene, and will occur repeatedly in the future. The crust of China consists of several plates or blocks. Their boundaries are mostly large fault zones. Quaternary active faults have been forming and developing along the zones under the united effect of India Plate's collision towards NNE and Pacific Plate's subduction towards W. Southwest China is an area where SEOS are concentrated. During Q 1 and Q 2, the Sichuan-Yunnan (Rhombus) Block was pushed to SSE, so that left lateral strike slipping took place in the Xianshuihe Fault Zone and Xiaojiang Fault Zone. Some fault basins were formed in the tensional areas nearby these zones. During Q 3, due to change of tectonic stress direction, Xiaojiang Fault Zone linked with Xianshuihe Fault Zone and formed a huge curve fault zone, where a lot of SEOS are located. Activation of faults in Q 3 has an universal significance. All the faults last to the current time, and the faults are called active faults for this reason, SEOS are located at specific sections of the active faults. Epicenters in SEOS express characteristics in the tectonophysics and geomorphology. Widely developed graben horst system, long range of remaining fault hills, head cut rivers, remarkable differential in relief by accending and descending of the operate fault banks in the area where strong earthquakes occurred, are some obvious samples. In SEOS, strong earthquakes of similar magnitudes repeated in the same places in certain temporal interval. The model of the processes is "breaking-healing-breaking again-healing again". According to the similarity of the map patterns of iso value of acceleration of Jiji Earthquake (9.21. 1999, Taiwan, China) and the iso intensity for Yuzha Earthquake (1955, Sichuan, China), evident differences of buildings damage between in fault zones and out of fault zones and deformation of young deposition layers, the deformation mechanics of the strong earthquakes can be generalized as follows: 1. SEOS have a three layer structure: a rupture layer and two complete rock layers as the fault walls located on two sides of the rupture layer. 2. The rupture layer is a place where tectonic stress is concentrated and released. It plays the role of reflecting seismic wave propagation. 3. Strong earthquakes repeat in certain temporal interval and spatial scope. Determining SEOS and utilizing fully the features mentioned above are very important for engineering construction.
The term strong earthquake occuring sections (SEOS) is used to specify those places where strong earthquakes (M≥6) have occurred since Holocene, and will occur repeatedly in the future. The crust of China consists of several plates or blocks. Their boundaries are mostly large fault zones. Quaternary active faults have been forming and developing along the zones under the united effect of India Plate's collision towards NNE and Pacific Plate's subduction towards W. Southwest China is an area where SEOS are concentrated. During Q 1 and Q 2, the Sichuan-Yunnan (Rhombus) Block was pushed to SSE, so that left lateral strike slipping took place in the Xianshuihe Fault Zone and Xiaojiang Fault Zone. Some fault basins were formed in the tensional areas nearby these zones. During Q 3, due to change of tectonic stress direction, Xiaojiang Fault Zone linked with Xianshuihe Fault Zone and formed a huge curve fault zone, where a lot of SEOS are located. Activation of faults in Q 3 has an universal significance. All the faults last to the current time, and the faults are called active faults for this reason, SEOS are located at specific sections of the active faults. Epicenters in SEOS express characteristics in the tectonophysics and geomorphology. Widely developed graben horst system, long range of remaining fault hills, head cut rivers, remarkable differential in relief by accending and descending of the operate fault banks in the area where strong earthquakes occurred, are some obvious samples. In SEOS, strong earthquakes of similar magnitudes repeated in the same places in certain temporal interval. The model of the processes is "breaking-healing-breaking again-healing again". According to the similarity of the map patterns of iso value of acceleration of Jiji Earthquake (9.21. 1999, Taiwan, China) and the iso intensity for Yuzha Earthquake (1955, Sichuan, China), evident differences of buildings damage between in fault zones and out of fault zones and deformation of young deposition layers, the deformation mechanics of the strong earthquakes can be generalized as follows: 1. SEOS have a three layer structure: a rupture layer and two complete rock layers as the fault walls located on two sides of the rupture layer. 2. The rupture layer is a place where tectonic stress is concentrated and released. It plays the role of reflecting seismic wave propagation. 3. Strong earthquakes repeat in certain temporal interval and spatial scope. Determining SEOS and utilizing fully the features mentioned above are very important for engineering construction.
引文
[1] 李,汪良谋.云南川西地区地震地质基本特征的探讨.地震科学,1975,(4):308325.[LiPing,WangLiangmou.Explorationoftheseismo geologicalfeaturesoftheYunnan-WestSichuanregion.ScientiaGeologicaSinica,1975,(4):308325.]
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[3] 李,主编.鲜水河———小江断裂带.周玖,黄修武,执笔,地震出版社.1993.1821.[LiPing.Xianshuihe-Xiaojiangfaultzone,SeismologicalPublishingHouse,1993.1821.]
[4] BiChingchang(毕庆昌).TaiwanencyclopediaofEuropeanandAsianregionalgeology.In:MooresEM&RhodesW ,eds.London:FairbridgeandPublishedbyChapman&Hall,1997,711717.
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[6] LuHuafu,YuHongnian,DingYouwen,ZhangQinglong.ChangingstressfieldinthemiddlesegmentoftheTanLufaultzone,EasternChina.Tectonophysics.1983,98,253270.
[7] (a)国家地震局业务组.世界大地震简目(1904-1972)(震级≥7)1973.2.;(b)国家地震局编.中国强震简目(公元前7801976.8.31,M≥6级),地震出版社,1997.[(a)BriefCatalogueoflargeearthquakes(1904-1972,M≥7)intheworld,1973;(b)Briefcatalogueofstrongearthquakes(B .c780-1976,M≥6)ofChina.SeismologicalPublishingHouse,1977.]
[8] 高名修,著.东亚北东向块断构造与现代地裂运动.地震出版社,1995,5262;169.[GaoMingxiu,ed.Fault blockstructureinNEpartofeastAsiaandrecentcrustbreaking.Beijing:SeismologicalPublishingHouse,1995,5262.]
[9] 张晶,孙柏成,张成强.唐山地震的重力异常及其震后变化.地震,1998,18(3):293298.[ZhangJing,SunBaicheng,ZhangChengqiang.GravityanomalybeforeTangshanearthquakeandgravitychangesaftertheearthquake.Earthquake,1998,18(3):293298.]
[10] 吴雪芳.重力方法在地震预报中的作用.地震,1996,16(1):9095.[WuXuefang.Significanceofgravitymethodinearthquakeprediction.Earthquake,1996,16(1):9095.]
[11] 葛道凯,崔之久,伍永秋,刘耕年,阴家润,许清海,庞其清.从昆仑山垭口地区上新世—更新世沉积相与生物圈的变化看青藏高原隆起.见:青藏项目专家委员会编.青藏高原形成演化、环境变迁与生态系统研究.科学出版社,1996,8594.[GeDaokai,CuiZhijiu,WuYongqiu,etal.StudyonenvironmentalevolutioninthepassareaofKunlunMountainsduringPliocenetoPleistocene,northenQianghai-XizangPlateau,SorthwesternChina.Beijing:SciencePress.1996.]
[12] 国家地震局西南烈度队,著.川滇强震区地震地质调查汇编.地震出版社.1979,3536.[SouthwestIntensityGroup.CompilationofgeologicalinvestigationforSichuan—Yunnanstrongearthquakes.Beijing:SeismologicalPublishingHouse,1979,3536.]
[13] 任金卫,李.则木河断裂带北段地震地貌及古地震研究.地震地质,1989,11(1):2734.[RenJinwei,LiPing.Earthquake causedlandformsandpaleoseismicstudyontheNorthernsegmentoftheZemuhefault.SeismologyandGeolo gy,1989,11(1):2734.]
[14] 闻学译,杜平山,龙德雄.安宁河断裂带小相岭段古地震的新证据及最晚事件的年代.地震地质,2000,22(1):18.[WenXueze,DuPingshan,LongDexiong.NewevidenceofpaleoearthquakesanddateoflatesteventontheXiaoxianglingmountainsegmentoftheAnninghefaultzone.SeismologyandGeology,2000,22(1):18.]
[15] 陈睿,等.小江西支断裂和滑动速率与强震重复周期.地震地质,1988,2期.[ChenRui,etal.Slippingrateandrepeat ingperiodofstrongearthquakesalongthewestbranchofXiaojiangFaultZone.SeismologyandGeology,1988,No.2]
[16] 李,刘行松,杨美娥,苑京立.昔格达层构造变形形成因素分析.中国地震,1985,1(3):3946.[LiPing,LiuXing song,YangMeie,YuanJingli.AnalysisontheformativefactorsofthetectonicdeformationoftheXigedaGroup.Earth guakeResearchinChina,1985,1(3):3946.]
[17] 唐荣昌,等.四川活动断裂与地震.地震出版社,1993,附件9298.[TangRongchang,etal.Activefaultsandearth quakesinSichuanProvince.Beijing:SeismologicalPublishingHouse,1993,App.9298.]
[2] 陈俊勇,张骥,薛璋,张江齐.珠穆朗玛峰地区的地壳运动及有关问题的探讨.地球物理学报,1996,39(1):5867.[ChenJunyong,ZhangJi,XueZhang,ZhangJiangqi.OnthecrustalmovementinZhumulangmaFenganditsadjiacentarea,ActaGeophysicaSinica,1996,39(1):5867.]
[3] 李,主编.鲜水河———小江断裂带.周玖,黄修武,执笔,地震出版社.1993.1821.[LiPing.Xianshuihe-Xiaojiangfaultzone,SeismologicalPublishingHouse,1993.1821.]
[4] BiChingchang(毕庆昌).TaiwanencyclopediaofEuropeanandAsianregionalgeology.In:MooresEM&RhodesW ,eds.London:FairbridgeandPublishedbyChapman&Hall,1997,711717.
[5] 何春荪,编著.台湾地质概论,台湾地质图说明书.(台湾)经济部中央地质调查所出版,增订第二版,1986.[HoCS ,ed.GeneralgeologicoutlineofTaiwanandexplanationtogeologicmapofTaiwan.PublishedbyCentralGeologicalSurveyofTaiwan,1986.]
[6] LuHuafu,YuHongnian,DingYouwen,ZhangQinglong.ChangingstressfieldinthemiddlesegmentoftheTanLufaultzone,EasternChina.Tectonophysics.1983,98,253270.
[7] (a)国家地震局业务组.世界大地震简目(1904-1972)(震级≥7)1973.2.;(b)国家地震局编.中国强震简目(公元前7801976.8.31,M≥6级),地震出版社,1997.[(a)BriefCatalogueoflargeearthquakes(1904-1972,M≥7)intheworld,1973;(b)Briefcatalogueofstrongearthquakes(B .c780-1976,M≥6)ofChina.SeismologicalPublishingHouse,1977.]
[8] 高名修,著.东亚北东向块断构造与现代地裂运动.地震出版社,1995,5262;169.[GaoMingxiu,ed.Fault blockstructureinNEpartofeastAsiaandrecentcrustbreaking.Beijing:SeismologicalPublishingHouse,1995,5262.]
[9] 张晶,孙柏成,张成强.唐山地震的重力异常及其震后变化.地震,1998,18(3):293298.[ZhangJing,SunBaicheng,ZhangChengqiang.GravityanomalybeforeTangshanearthquakeandgravitychangesaftertheearthquake.Earthquake,1998,18(3):293298.]
[10] 吴雪芳.重力方法在地震预报中的作用.地震,1996,16(1):9095.[WuXuefang.Significanceofgravitymethodinearthquakeprediction.Earthquake,1996,16(1):9095.]
[11] 葛道凯,崔之久,伍永秋,刘耕年,阴家润,许清海,庞其清.从昆仑山垭口地区上新世—更新世沉积相与生物圈的变化看青藏高原隆起.见:青藏项目专家委员会编.青藏高原形成演化、环境变迁与生态系统研究.科学出版社,1996,8594.[GeDaokai,CuiZhijiu,WuYongqiu,etal.StudyonenvironmentalevolutioninthepassareaofKunlunMountainsduringPliocenetoPleistocene,northenQianghai-XizangPlateau,SorthwesternChina.Beijing:SciencePress.1996.]
[12] 国家地震局西南烈度队,著.川滇强震区地震地质调查汇编.地震出版社.1979,3536.[SouthwestIntensityGroup.CompilationofgeologicalinvestigationforSichuan—Yunnanstrongearthquakes.Beijing:SeismologicalPublishingHouse,1979,3536.]
[13] 任金卫,李.则木河断裂带北段地震地貌及古地震研究.地震地质,1989,11(1):2734.[RenJinwei,LiPing.Earthquake causedlandformsandpaleoseismicstudyontheNorthernsegmentoftheZemuhefault.SeismologyandGeolo gy,1989,11(1):2734.]
[14] 闻学译,杜平山,龙德雄.安宁河断裂带小相岭段古地震的新证据及最晚事件的年代.地震地质,2000,22(1):18.[WenXueze,DuPingshan,LongDexiong.NewevidenceofpaleoearthquakesanddateoflatesteventontheXiaoxianglingmountainsegmentoftheAnninghefaultzone.SeismologyandGeology,2000,22(1):18.]
[15] 陈睿,等.小江西支断裂和滑动速率与强震重复周期.地震地质,1988,2期.[ChenRui,etal.Slippingrateandrepeat ingperiodofstrongearthquakesalongthewestbranchofXiaojiangFaultZone.SeismologyandGeology,1988,No.2]
[16] 李,刘行松,杨美娥,苑京立.昔格达层构造变形形成因素分析.中国地震,1985,1(3):3946.[LiPing,LiuXing song,YangMeie,YuanJingli.AnalysisontheformativefactorsofthetectonicdeformationoftheXigedaGroup.Earth guakeResearchinChina,1985,1(3):3946.]
[17] 唐荣昌,等.四川活动断裂与地震.地震出版社,1993,附件9298.[TangRongchang,etal.Activefaultsandearth quakesinSichuanProvince.Beijing:SeismologicalPublishingHouse,1993,App.9298.]
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