昆仑山口西8.1级地震地表破裂参数相互关系的新认识
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摘要
地震地表破裂带调查表明,昆仑山口西 8. 1级地震的破裂长度为 426km,最大水平位移6m左右,地震破裂位移的分布明显地受断层活动段控制。该次地震的破裂长度远大于统计值,文中应用地壳极限线应变的概念,通过比较中国大陆内部几次走滑型强震的地震破裂最大位移与破裂长度的关系,论述了昆仑山口西 8. 1级地震中各次级段破裂的相对独立特征,认为该次强震不是一次整体性破裂事件,而是由连续触发的几次地震组成。
The Kunlunshan M S 8.1 earthquake of 2001 is a large earthquake produced by a large-scale intraplate strike slip faulting. Field observation shows that the surface rupture of this earthquake is about 426km long, and the maximum sinistral displacement is about 6m. As compared with the other similar intraplate large earthquakes, its rupture length is extraordinarily longer but its horizontal displacement is relatively small. The distribution of horizontal displacement along the surface ruptures is markedly controlled by fault structure. At the section where the horizontal displacement is small, the vertical displacement is also smaller, and no transformation of horizontal and vertical displacements is observed. This feature is also different from that of the other earthquakes. The relationship among rupture length, displacement and seismic magnitude follows a certain empirical equation, in which the ratio between the average displacement amount and rupture length is called “Ultimate linear strain”, and is constantly within the range of 10 -5 for the rupture in the earth's crust. This feature can be used as criterion for testing the independency and integrality of the rupture segments. In this paper, we calculated the “ultimate linear strain” of the entire rupture zones and sub-segments of several large earthquakes, including the 1920 Haiyuan earthquake, 1951 Bong Co earthquake, 1932 Changma earthquake and 2001 Kunlunshan earthquake. The results show that average values of ultimate linear strain of the Haiyuan, Bong Co and Changma earthquakes are approximately close to the statistic value, but the values of ultimate linear strain of their sub-segments are significantly higher. In contrast, the value of ultimate linear strain for the entire surface rupture of the Kunlunshan earthquake is much lower than the statistic value, but the values of ultimate linear strain of its four sub-segments, except the west Taiyanghu segments, are close to the statistic value. Therefore, the Kunlunshan earthquake (M S 8.1) should be produced by four relatively independent faulting events, instead of a uniform faulting. These characters provide geological evidence supporting the deduction that the Kunlunshan earthquake is successively triggered multiple earthquake events, rather than a single earthquake.
The Kunlunshan M S 8.1 earthquake of 2001 is a large earthquake produced by a large-scale intraplate strike slip faulting. Field observation shows that the surface rupture of this earthquake is about 426km long, and the maximum sinistral displacement is about 6m. As compared with the other similar intraplate large earthquakes, its rupture length is extraordinarily longer but its horizontal displacement is relatively small. The distribution of horizontal displacement along the surface ruptures is markedly controlled by fault structure. At the section where the horizontal displacement is small, the vertical displacement is also smaller, and no transformation of horizontal and vertical displacements is observed. This feature is also different from that of the other earthquakes. The relationship among rupture length, displacement and seismic magnitude follows a certain empirical equation, in which the ratio between the average displacement amount and rupture length is called “Ultimate linear strain”, and is constantly within the range of 10 -5 for the rupture in the earth's crust. This feature can be used as criterion for testing the independency and integrality of the rupture segments. In this paper, we calculated the “ultimate linear strain” of the entire rupture zones and sub-segments of several large earthquakes, including the 1920 Haiyuan earthquake, 1951 Bong Co earthquake, 1932 Changma earthquake and 2001 Kunlunshan earthquake. The results show that average values of ultimate linear strain of the Haiyuan, Bong Co and Changma earthquakes are approximately close to the statistic value, but the values of ultimate linear strain of their sub-segments are significantly higher. In contrast, the value of ultimate linear strain for the entire surface rupture of the Kunlunshan earthquake is much lower than the statistic value, but the values of ultimate linear strain of its four sub-segments, except the west Taiyanghu segments, are close to the statistic value. Therefore, the Kunlunshan earthquake (M S 8.1) should be produced by four relatively independent faulting events, instead of a uniform faulting. These characters provide geological evidence supporting the deduction that the Kunlunshan earthquake is successively triggered multiple earthquake events, rather than a single earthquake.
引文
①中国地震局昆仑山口西81级地震综合科学考察队,2003,昆仑山口西81级地震综合科学考察报告
陈文彬,徐锡伟,张志坚,等.2001.2001年11月14日青新交界MS8.1地震地表破裂带的初步调查[J].西北地震学报,23(4):313—317.
CHENWen bin,XUXi wei,ZHANGZhi jian, etal.2001.PreparatoryfieldinvestigationonthesurfacedeformationzoneoftheQinghaiXinjiangMS 8.1earthquakeonNov.14,2001[J].NorthweternSeismologicalJournal,23(4):313—317(inChinese).
党光明,王赞军.2002.青海昆仑山口西MS 8.1级地震地表破裂带特征与主要震害[J].地质通报,21(2):105—120.
DANGGuang ming,WANGZan jun.2002.CharacteristicsofthesurfacerupturezoneandmainseismichazardscausedbytheMS8.1earthquakewestoftheKunlunPass[J].GeologicalBulletinofChina,21(2):105—120(inChinese).
邓起东,于贵华,叶文华.1992.地震地表破裂参数与震级关系的研究[A].见:国家地震局地质研究所编.活动断裂研究(2).北京:地震出版社.247—264.
DENGQi dong,YUGui hua,YEWen hua.1992.Relationshipbetweenearthquakemagnitudeandparametersofsur facerupturesassociatedwithhistoricalearthquakes[A].In:InstituteofGeology,SSB(ed).ResearthonActiveFault(2).SeismologicalPress,Beijing.247—264(inChinese).
丁国瑜,田勤俭,孔凡臣,等著.1993.活断层分段:原则、方法及应用[M].北京:地震出版社.143.
DINGGuo yu,TIANQin jian,KONGFan chen, etal.1993.SegmentationofActiveFault:Principle,MethodologyandApplication[M].SeismologicalPress,Beijing.143(inChinese).
国家地震局地质研究所,宁夏回族自治区地震局.1990.海原活动断裂带[M].北京:地震出版社.286.
InstituteofGeology,StateSeismologicalBureau,SeismologicalBureauofNingxiaHuiAutonomousRegion.1990.TheHaiyuanActiveFaultZone[M].SeismologicalPress,Beijing.286(inChinese).
国家地震局地质研究所.1992.西藏中部活动断层[M].北京:地震出版社.
InstituteofGeology,StateSeismologicalBureau.1992.ActiveFaultsinCentralTibet[M].SeismologicalPress,Bei jing(inChinese).
国家地震局兰州地震研究所.1992.昌马活动断裂带[M].北京:地震出版社.207.
LanzhouInstituteofSeismology,StateSeismologicalBureau.1992.TheChangmaActiveFaultZone[M].Seismologi calPress,Beijing.207(inChinese).
王赞军,党光明,张瑞斌,等.2002.昆仑山口西MS 8.1级地震地表破裂的类型与性质[J].高原地震,14(1):17—25.
WANGZan jun,DANGGuang ming,ZHANGRui bin, etal.2002.StylesandcharacteristicsofthesurfaceruptureoftheWestKunlunMountainsEarthquakewithMS8.1[J].EarthquakeResearchinPlateau,14(1):17—25(inChinese).
新疆维吾尔自治区地震局.1985.富蕴地震断裂带[M].北京:地震出版社.33—53.
SeismologicalBureauofXinjiangUygurAutonomousRegion.1985.TheFuyunEarthquakeFaultZone[M].Seismo logicalPress,Beijing.33—53(inChinese).
许力生,陈运泰.2001.2001年11月14日昆仑山口西8.1级大地震简介[J].震情研究,51(4):80—82.
XULi sheng,CHENYun tai.2001.BriefintroductionofthewestofKunlunshanPassearthquakewithmagnitude8.1occurredonNov.14in2001[J].ResearchonEarthquakeSituation,51(4):80—82(inChinese).
徐锡伟,陈文彬,于贵华,等.2002.2001年11月14日昆仑山库赛湖地震(MS8.1)地表破裂带的基本特征[J].地震地质,24(1):1—13.
XUXi wei,CHENWen bin,YUGui hua, etal.2002.CharacteristicfeaturesofthesurfacerupturesoftheHohSaiHu(Kunlunshan)earthquake(MS 8.1), northernTibetanPlateau,China[J].SeismologyandGeology,24(1):1—13(inChinese).
叶文华.1985.震源参数与地震震级的关系[J].地震研究,8(2):147—158.
YEWen hua.1985.Relationshipbetweenthefocalparametersandtheearthquakemagnitude[J].JournalofSeismo logicalResearch,8(2):147—158(inChinese).
张立人.1993.断层破裂长度、位移与震级和断层的破裂分段[A].见:丁国瑜等著.活断层分段.北京:地震出版社.30—38.
ZHANGLi ren.1993.Rupturelength, displacement, magnitudeandfaultsegmentation[A].In:DINGGuo yuetal(eds).SegmentationofActiveFault.SeismologicalPress,Beijing.30—38(inChinese).
张郢珍,张立人,粟生平,等.1991.地壳极限应变与危险区强震发生的概率估计[J].中国地震,7(2):31—36.
ZHANGYing zhen,ZHANGLi ren,LISheng ping, etal.1991.Ultimatestrainofcrustandtheprobabilityofstrongearthquakeinpotentialareas[J].EarthquakeResearchinChina,7(2):31—36(inChinese).
赵瑞斌,李军,向志勇,等.2002.昆仑山口西8.1级地震地壳破裂带西段考察[J].内陆地震,16(2):175—179.
ZHAORui bin,LIJun,XIANGZhi yong, etal.2002.ExpeditiononthewestsegmentofthesurfacerupturezoneoftheMS8.1earthquakeinthewestofKunlunMountainPass[J].InlandEarthqukae,16(2):175—179(inChinese).
JonseLM,Wei binHan.1984.FocalmechanismandaftershocklocationoftheSongpanearthquakesofAugust1976inSichuan,China[J].JourGeophyRes,89(B9):7697—7707.
LinA,FuR,GuoJ, etal.2002.Co seismicstrike slipandrupturelengthproducedbythe2001MS8.1centralKun lunearthquake[J].Science,296:2015—2017.
ParsonsT,TodaS,SteinRS, etal.2000.HeightenedoddsoflargeearthquakesnearIstanbul:Aninteraction basedprobabilitycalculation[J].Science,288:661—665.
RikitateT.1984.Strainrateofactivefaultandearthquakerisk[J].EarthqPredictRec,2(4):277—302.
SlemmonsDB.1982.Determinationofdesignearthquakemagnitudesformicrozonation[A].In:The3rdInternationalEarthquakeMicrozonationConferenceProceedings.199—130.
SteinRS,KingGCP,LinJ.1992.ChangeinfailurestressonthesouthernSanAndreasFaultsystemcausedbythe1992magnitude=7.4Landersearthquake[J].Science,258:1328—1332.
WellsDL,CoppersmithKJ.1994.Updatedempiricalrelationshipsamongmagnitude, rupturelength, rupturearea,andsurfacedisplacement[J].BullSeismSocAm,947—1002.
XuXW,ChenW,MaW, etal.2002.SurfaceruptureoftheKunlunshanearthquake(MS 8.1),NorthernTibetanPlateau,China[J].SeismResLett,3(6):884—892.
陈文彬,徐锡伟,张志坚,等.2001.2001年11月14日青新交界MS8.1地震地表破裂带的初步调查[J].西北地震学报,23(4):313—317.
CHENWen bin,XUXi wei,ZHANGZhi jian, etal.2001.PreparatoryfieldinvestigationonthesurfacedeformationzoneoftheQinghaiXinjiangMS 8.1earthquakeonNov.14,2001[J].NorthweternSeismologicalJournal,23(4):313—317(inChinese).
党光明,王赞军.2002.青海昆仑山口西MS 8.1级地震地表破裂带特征与主要震害[J].地质通报,21(2):105—120.
DANGGuang ming,WANGZan jun.2002.CharacteristicsofthesurfacerupturezoneandmainseismichazardscausedbytheMS8.1earthquakewestoftheKunlunPass[J].GeologicalBulletinofChina,21(2):105—120(inChinese).
邓起东,于贵华,叶文华.1992.地震地表破裂参数与震级关系的研究[A].见:国家地震局地质研究所编.活动断裂研究(2).北京:地震出版社.247—264.
DENGQi dong,YUGui hua,YEWen hua.1992.Relationshipbetweenearthquakemagnitudeandparametersofsur facerupturesassociatedwithhistoricalearthquakes[A].In:InstituteofGeology,SSB(ed).ResearthonActiveFault(2).SeismologicalPress,Beijing.247—264(inChinese).
丁国瑜,田勤俭,孔凡臣,等著.1993.活断层分段:原则、方法及应用[M].北京:地震出版社.143.
DINGGuo yu,TIANQin jian,KONGFan chen, etal.1993.SegmentationofActiveFault:Principle,MethodologyandApplication[M].SeismologicalPress,Beijing.143(inChinese).
国家地震局地质研究所,宁夏回族自治区地震局.1990.海原活动断裂带[M].北京:地震出版社.286.
InstituteofGeology,StateSeismologicalBureau,SeismologicalBureauofNingxiaHuiAutonomousRegion.1990.TheHaiyuanActiveFaultZone[M].SeismologicalPress,Beijing.286(inChinese).
国家地震局地质研究所.1992.西藏中部活动断层[M].北京:地震出版社.
InstituteofGeology,StateSeismologicalBureau.1992.ActiveFaultsinCentralTibet[M].SeismologicalPress,Bei jing(inChinese).
国家地震局兰州地震研究所.1992.昌马活动断裂带[M].北京:地震出版社.207.
LanzhouInstituteofSeismology,StateSeismologicalBureau.1992.TheChangmaActiveFaultZone[M].Seismologi calPress,Beijing.207(inChinese).
王赞军,党光明,张瑞斌,等.2002.昆仑山口西MS 8.1级地震地表破裂的类型与性质[J].高原地震,14(1):17—25.
WANGZan jun,DANGGuang ming,ZHANGRui bin, etal.2002.StylesandcharacteristicsofthesurfaceruptureoftheWestKunlunMountainsEarthquakewithMS8.1[J].EarthquakeResearchinPlateau,14(1):17—25(inChinese).
新疆维吾尔自治区地震局.1985.富蕴地震断裂带[M].北京:地震出版社.33—53.
SeismologicalBureauofXinjiangUygurAutonomousRegion.1985.TheFuyunEarthquakeFaultZone[M].Seismo logicalPress,Beijing.33—53(inChinese).
许力生,陈运泰.2001.2001年11月14日昆仑山口西8.1级大地震简介[J].震情研究,51(4):80—82.
XULi sheng,CHENYun tai.2001.BriefintroductionofthewestofKunlunshanPassearthquakewithmagnitude8.1occurredonNov.14in2001[J].ResearchonEarthquakeSituation,51(4):80—82(inChinese).
徐锡伟,陈文彬,于贵华,等.2002.2001年11月14日昆仑山库赛湖地震(MS8.1)地表破裂带的基本特征[J].地震地质,24(1):1—13.
XUXi wei,CHENWen bin,YUGui hua, etal.2002.CharacteristicfeaturesofthesurfacerupturesoftheHohSaiHu(Kunlunshan)earthquake(MS 8.1), northernTibetanPlateau,China[J].SeismologyandGeology,24(1):1—13(inChinese).
叶文华.1985.震源参数与地震震级的关系[J].地震研究,8(2):147—158.
YEWen hua.1985.Relationshipbetweenthefocalparametersandtheearthquakemagnitude[J].JournalofSeismo logicalResearch,8(2):147—158(inChinese).
张立人.1993.断层破裂长度、位移与震级和断层的破裂分段[A].见:丁国瑜等著.活断层分段.北京:地震出版社.30—38.
ZHANGLi ren.1993.Rupturelength, displacement, magnitudeandfaultsegmentation[A].In:DINGGuo yuetal(eds).SegmentationofActiveFault.SeismologicalPress,Beijing.30—38(inChinese).
张郢珍,张立人,粟生平,等.1991.地壳极限应变与危险区强震发生的概率估计[J].中国地震,7(2):31—36.
ZHANGYing zhen,ZHANGLi ren,LISheng ping, etal.1991.Ultimatestrainofcrustandtheprobabilityofstrongearthquakeinpotentialareas[J].EarthquakeResearchinChina,7(2):31—36(inChinese).
赵瑞斌,李军,向志勇,等.2002.昆仑山口西8.1级地震地壳破裂带西段考察[J].内陆地震,16(2):175—179.
ZHAORui bin,LIJun,XIANGZhi yong, etal.2002.ExpeditiononthewestsegmentofthesurfacerupturezoneoftheMS8.1earthquakeinthewestofKunlunMountainPass[J].InlandEarthqukae,16(2):175—179(inChinese).
JonseLM,Wei binHan.1984.FocalmechanismandaftershocklocationoftheSongpanearthquakesofAugust1976inSichuan,China[J].JourGeophyRes,89(B9):7697—7707.
LinA,FuR,GuoJ, etal.2002.Co seismicstrike slipandrupturelengthproducedbythe2001MS8.1centralKun lunearthquake[J].Science,296:2015—2017.
ParsonsT,TodaS,SteinRS, etal.2000.HeightenedoddsoflargeearthquakesnearIstanbul:Aninteraction basedprobabilitycalculation[J].Science,288:661—665.
RikitateT.1984.Strainrateofactivefaultandearthquakerisk[J].EarthqPredictRec,2(4):277—302.
SlemmonsDB.1982.Determinationofdesignearthquakemagnitudesformicrozonation[A].In:The3rdInternationalEarthquakeMicrozonationConferenceProceedings.199—130.
SteinRS,KingGCP,LinJ.1992.ChangeinfailurestressonthesouthernSanAndreasFaultsystemcausedbythe1992magnitude=7.4Landersearthquake[J].Science,258:1328—1332.
WellsDL,CoppersmithKJ.1994.Updatedempiricalrelationshipsamongmagnitude, rupturelength, rupturearea,andsurfacedisplacement[J].BullSeismSocAm,947—1002.
XuXW,ChenW,MaW, etal.2002.SurfaceruptureoftheKunlunshanearthquake(MS 8.1),NorthernTibetanPlateau,China[J].SeismResLett,3(6):884—892.
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