第5章活斷層地震130428

工程地質(zhì)學(xué)活斷層地震水庫(kù)誘發(fā)地震活斷層的工程地質(zhì)意義活斷層：一般理解為目前還在持續(xù)活動(dòng)的斷層，或在歷史時(shí)期或近期地質(zhì)時(shí)期（11000a～35000a間）活動(dòng)過(guò)、極有可能在不遠(yuǎn)的將來(lái)（一般理解為重要建筑物如大壩、核電站的使用年限之內(nèi)，約100a～

200a）重新活動(dòng)的斷層。⒉活動(dòng)特點(diǎn)蠕滑（穩(wěn)滑）——持續(xù)不斷緩慢蠕動(dòng)粘滑——間斷性、周期性突然錯(cuò)斷，常伴有地震TheLandersfault(redlinesatleft)andtheHectorMinefaultanditsaftershocks(redlinesandcirclesatright).TheHectorMineearthquakewasamagnitude7.1,anditproducedthousandsofaftershocks.(ImagecourtesyofEgillHauksson,Caltech)⒊活動(dòng)強(qiáng)度以錯(cuò)動(dòng)速率判定速率變化特點(diǎn)相當(dāng)緩慢，1mm/a已屬?gòu)?qiáng)活動(dòng)斷層圣安德列斯斷層（最有名的）僅5cm/a

SanAndreasFaultThroughCarrizoPlainTheSanAndreasfaultcutsspectacularlyacrosstheCarrizoPlainofCaliforniainthisviewlookingtothenorthwesttowardSodaLake(whitesaltflatvisibleonthehorizon).StreamsdrainingofftheTemblorRangetotheeast(lowerrightofpicture)areoffsettothenorthbyright-lateralstrike-slipfaultmotionalongtheSanAndreas.TheSanAndreasmarkstheboundarybetweenthePacificPlatetothewestandtheNorthAmericanPlatetotheeast,andisamongthemostactivefaultsystemsintheworld.Geologistsbelievethatthetotalaccumulateddisplacementfromearthquakesandcreepisatleast550kilometersalongtheSanAndreasfaultsinceitcameintobeingabout15-20millionyearsago.TheentireSanAndreasfaultsystemismorethan1300kilometerslongandextendstodepthsofatleast16kilometerswithintheEarth.Indetail,thefaultisacomplexzoneofcrushedandbrokenrockfromafewhundredmeterstoseveralkilometerswide.ManysmallerfaultsbranchfromandjointheSanAndreasfaultzone.⒋活動(dòng)性斷層判定標(biāo)志⑴最新沉積層被錯(cuò)斷（Q3以來(lái)的地層直接測(cè)量數(shù)據(jù)）美國(guó)南加州莫哈維沙漠中的圣安德烈亞斯斷層的活動(dòng)，將第四系中的溝壑錯(cuò)開(kāi)圖中充當(dāng)標(biāo)尺的小伙是UCDavis地質(zhì)系大地構(gòu)造專(zhuān)業(yè)研究生PeterGold，何鵬攝于2009年4月26日斷層錯(cuò)動(dòng)方向⑵地形地貌標(biāo)志（古建筑被錯(cuò)斷山地、平原地貌突變等）⑶斷層物質(zhì)絕對(duì)年齡測(cè)試結(jié)果⒌研究意義·它的活動(dòng)會(huì)直接損害跨斷層修建或與斷層鄰近的建筑物ThetownofHollisterhasthedubiousdistinctionofhavingbeenbuiltdirectlyontopofanactivecreepingfault.TheCalaverasFault,whichbranchesofffromtheSanAndreasfaultabout20milessouthoftown,iscreepingbitbybit,slowlytearinghousesandstreetsapart.Inthephotoleft,thepinklinecorrespondstotheapproximatetraceofthefault.Clickonthenumberstoseecloseupsoftheeffectsoffaultcreep.ThefoundationofthishousesitsdirectlyonthetraceoftheCalaverasFault,whichcanbeseenastheprominentcrackinthestreetatthebaseofthephotograph.Differentialwarpingofthefoundationiscausingthehousetotilt.MovementontheCalaverasFaultisrightlateral,sothattherightsideofthehouseismovingtowardsthephotographer'sposition,whiletheleftsideismovingaway.Noticetheoverlapping(andprogressivelymorerecent)repairstotheasphaltinthestreet.ThishousewasconstructedonthetraceoftheCalaverasfault,whichrunsacrossthepicture.Thesteps,porchandfarsideofthehousearemovingtotheright,relativetotheremainderofthehouseinfrontoftheporch(rightlateralstrike-slipmotion).Themovementcanbeseeninthewarpingofthewallnearthebuildingfoundation.Therightlateraloffsetcanalsobeclearlyseenintheoffsetcurbbelow.Cumulativemovementovertimecanirreparablydamageahouse.Severalhomeownersreportthattheyhadtohavetheirhousesliftedofftheoldfoundation,whichwasthenreplacedbyanewfoundation.Theretainingwall,sidewalkandcurbswerealloriginallystraight,andhavebeenoffsetinarightlateralsensebycreepalongtheCalaverasFault.Youmaycomparethephotobelowontheright,takenin2001withtheonebelowleft,takeninabout1990.Isanymajordifferencevisible?No,thiswasnottreerootdamage!Thesidewalkisoffsetabout0.5cminarightlateralsense,andisinlinewiththefaulttraceinthepreviouspictures.·伴生地震使大范圍內(nèi)建筑物受損專(zhuān)家：兩大斷層之間擠壓頻繁洛杉磯隨時(shí)大地震

據(jù)媒體綜合報(bào)道，美國(guó)地震學(xué)家近日說(shuō)，美國(guó)洛杉磯市不久可能發(fā)生地震，因?yàn)槲惶幠霞又輧纱髷鄬又g的圣蓋博山和洛杉磯市中心，地層下方壓力不斷聚積，能量一旦釋放便會(huì)造成地震。強(qiáng)度可達(dá)里氏6.7級(jí)，但無(wú)法預(yù)測(cè)何時(shí)發(fā)生。美國(guó)太空總署噴氣推進(jìn)實(shí)驗(yàn)室地震專(zhuān)家阿格斯上周四發(fā)表聲明，指洛杉磯可能發(fā)生的地震屬于中度規(guī)模。阿格斯的研究發(fā)現(xiàn)，圣蓋博山下層的西拉瑪?shù)氯鸷臀挥诼迳即壥袇^(qū)地下的朋地岡兩大斷層擠壓頻繁，能量釋放速度為一年0.2英寸，相當(dāng)可觀。南加州大學(xué)華裔地震專(zhuān)家酈永剛同意阿格斯的說(shuō)法，酈永剛的研究發(fā)現(xiàn)，洛杉磯位處圣安德里斯和圣哈辛多兩大斷層上，地震頻率非常高，南北兩斷層擠壓產(chǎn)生能量，一邊釋放造成另一邊積壓，這種規(guī)模為里氏3級(jí)或以下的地震幾乎每天發(fā)生，但是一般人通常感受不到。

美國(guó)專(zhuān)家稱(chēng)洛杉磯極有可能遭毀滅性大地震據(jù)美聯(lián)社報(bào)道，美國(guó)地質(zhì)勘探局地震專(zhuān)家瓊斯至今記憶猶新，2001年8月，就在“9·11”恐怖襲擊之前，她參加了由美國(guó)聯(lián)邦緊急措施署召開(kāi)的一個(gè)緊急情況訓(xùn)練研討會(huì)。會(huì)議列出了最有可能威脅美國(guó)的三大潛在災(zāi)難：一是紐約發(fā)生恐怖襲擊，二是新奧爾良遭遇超強(qiáng)颶風(fēng)，三是圣安德烈亞斯斷層(加利福尼亞州地帶)發(fā)生大地震。截至目前，前兩大潛在災(zāi)難不幸被言中，都已經(jīng)變成無(wú)法挽回的事實(shí)，只剩下最后一項(xiàng)大災(zāi)難還未出現(xiàn)。瓊斯和其他地震專(zhuān)家想借“卡特里娜”颶風(fēng)的契機(jī)對(duì)加州如何預(yù)防大地震做全面評(píng)估。瓊斯和其他地震專(zhuān)家同時(shí)指出，過(guò)去20年間，加州很少遭遇地震襲擊，這是非常幸運(yùn)的一件事，但是，這并不代表加州以后都能平安無(wú)事。南加利福尼亞地震災(zāi)害小組預(yù)測(cè)，2024年以前，南加州發(fā)生里氏七級(jí)以上地震的可能性高達(dá)80%到90%，可以說(shuō)大災(zāi)難就在眼前。比“卡特里娜”可怕其實(shí)，美國(guó)加利福尼亞州居民長(zhǎng)期以來(lái)一直認(rèn)為，一場(chǎng)空前的大劫難“大地震”正在該州赫赫有名的圣安德烈亞斯斷層下面蠢蠢欲動(dòng)。美國(guó)地質(zhì)學(xué)家1999年在洛杉磯市普恩特丘陵地帶地下3公里處發(fā)現(xiàn)活性斷層，科研人員在今年6月25日根據(jù)不同震蕩方式模擬了多個(gè)場(chǎng)景，以確定該斷層引發(fā)大地震后可能造成的損失。他們發(fā)現(xiàn)，此類(lèi)地震可能使洛杉磯這座擁有900萬(wàn)人口的美國(guó)第二大城市毀于一旦。美國(guó)地質(zhì)勘探局地球物理學(xué)家菲爾德說(shuō)：“這場(chǎng)大地震帶來(lái)的經(jīng)濟(jì)損失將在8200萬(wàn)美元和2.52億美元之間，死亡人數(shù)將在3000到1.8萬(wàn)之間?！盩wooftheworld’smostearthquakeproneregions—TurkeyandIndonesia—experienceddamagingquakesinthefirstweekofJune2000.ThemapsontheleftshowthelocationofthetwoquakesplottedontheDigitalTectonicActivityMap(/dtam/data.html),acomprehensivedatabaseoffaultlines,earthquakezones,andvolcanismderivedfromgeologicalandsatellitedata.

Turkey,siteofamagnitude7.4earthquakein1999thatkilled18,000people,issandwichedbetweenthecollidingArabianandEurasianplates.ThecontinentalcrustunderneathTurkeyisbeingcompressedbythecollidingplates,forcingthebedrocktoshearalongfaultlines.Rocksontheoppositesidesofthefaultsaremovingrelativetoeachother.Earthquakesoccurwhentherocksalongthefaultmovesuddenly,releasingshockwavesthroughtheground.ThequakeofJune6,2000,(theleftone)occuredinCerkes,100km(60miles)northofAnkara,Turkey'scapital.Withamagnitudeof6.1,itkilled2peopleanddamagedmorethan100buildings.Amuchmoreseriousquake(therightone)strucktheIndonesianislandofSumatratwodaysearlier.Thatquakewaspoweredbyadifferentgeologicalmechanism.SoutheastofSumatratheoceaniccrustoftheAustralianplateisbeingforcedundertheIndonesianislandsinaprocesscalledsubduction.AstheoceanicplateisdrivendeeperunderneaththesurfaceoftheEarthitgeneratesearthquakesfarbeneaththeoceanfloor.

Bengkulu,Indonesia,washardesthitbythemagnitude8.0quake.Morethan100peoplewerekilledintheremoteregion,andalmostaweeklaterthefullextentofthecatastrophewasnotknown.龍門(mén)山斷裂帶綿竹5.12地震中毀壞的公路橋何鵬攝于2008年8月⒍活斷層區(qū)規(guī)劃設(shè)計(jì)建筑物的原則⑴

規(guī)劃選場(chǎng)·有低級(jí)別的活動(dòng)斷層的場(chǎng)地優(yōu)于有高級(jí)別的的場(chǎng)地;·盡可能避開(kāi)主斷層帶;·盡可能避開(kāi)正、逆斷層的上盤(pán)（此處地表變形強(qiáng)烈，分支、次生斷裂發(fā)育）;·有較大規(guī)模正、逆斷層，場(chǎng)地要選在距斷面數(shù)公里以外.Thedeveloperwantsthelandtobeasclosetodowntownaspossible,butfarawayfromactivefaults.ActiveorNot?ThatIsTheQuestionPurposeToevaluateseismicactivityalongmajorSanFranciscofaults.Materials1999Landsat7imageoftheSanFranciscoBayarea

faultmapoftheSanFranciscoBayarea

Youandacolleaguehavebeenhiredbyalocallanddevelopertohelpselectlandwherenewapartmentscanbebuilt.Thedeveloperwantsthelandtobeasclosetodowntownaspossible,butfarawayfromactivefaults.(Beingclosetoafaultisokayaslongasit'snotanactivefault.)Procedure·Andyouhavealsofoundagoodmapofthefaultsinthearea.·ForthisworkyouhaveselectedarecentimagefromLandsat7·youhaveaddedayellowmarktoshowthecenterofeachseismiceventthathasoccurredduringthepast100years·Comparethesatelliteimagewiththefaultmap.Lookforfaultsthatseemthemostactive.·Printoutthefaultmapanduseittomarkthespotwhereyourecommendplacingthenewapartments.·WriteashortparagraphinwhichyouexplainyourselectionTheadministrationbuildingattheBelmontLearningCenterwithanearthtrenchrunningpastitisshownWednesdayneardowntownLosAngeles.Multi-milliondollarhighschoolstraddlesquakefaultLOSANGELES,California(AP)--A$160millionhighschoolthathasneverbeenfinishedbecauseofsoilgasproblemsalsositsatopanearthquakefaultthatlikelyprecludesuseoftwobuildings,theschoolsuperintendentsaid.ThenewproblemdiscoveredatthedowntownBelmontLearningCentersiteappearedtoallbutdoomeffortstorevivetheprojectinitscurrentform.Extensiveremovaloftopsoilonthesiteandthepresenceofbuildingsandstreetsonadjacentlandpreventedseismologistsfromfindingunspoiledearthwithwhichtodeterminewhetherthefaultisactiveorinactive,SuperintendentRoyRomersaidWednesday.ThatmeansLosAngelesschoolofficialshavetoassumeitisactive,hesaid.Statelawsaysaschoolmaynotbebuiltwithin50feetofanactivefault."Thatisthebottomline,thatthedesignthatwehadforBelmontandwe'retryingtoexecuteisn'tgonnawork,itstraddlesthefault.Wehavetoreconsiderwhatwewereplanningtodohere,"Romersaid.MuchofBelmontwasbuiltbeforefearsabouttoxicgasesrisingfromtheoldoilfieldonwhichitwasbuiltbroughtconstructiontoahaltinJanuary2000."Wewillhavetoabandonthesebuildingsifwecannotprovethisisaninactivesite,"Romersaid.JamesMcConnell,thedistrict'schieffacilitiesexecutive,said$160millionhadbeenspentonBelmontasofMarch.Sincethenanother$6millionhasbeensenttostudythefeasibilityofrevivingthecampus,seismicstudiesandlegalwork.Romersaidalternativeswerebeingconsideredthatincludedreconfiguringbuildingsatthesiteandtakingsafetymeasuresthatcouldcost$70million.Anotherpossibility,hesaid,wasbuildinganewhighschoolon12acresoftheexistingsitethathassolidbedrock.Anew2,000seathighschoolcouldcost$60million.Hesaidanotheralternativewouldbetolookatothersitesinthearea.⑵建筑物類(lèi)型選擇

即使壩體部分被錯(cuò)開(kāi)3～5m，因壩體本身非常寬厚而且是柔性的，單純因錯(cuò)動(dòng)是不會(huì)破壞的。而混凝土壩都是堅(jiān)硬脆性的，任何有垂向分量的斷層錯(cuò)動(dòng)，即使是10～20mm的次級(jí)斷層錯(cuò)動(dòng)，必然導(dǎo)致或使壩、基分離，或使壩體破裂。當(dāng)場(chǎng)地有活斷層穿過(guò)，或場(chǎng)地位于正、逆斷層上盤(pán)只能建散體堆填壩，不宜建混凝土壩。（3）建筑物結(jié)構(gòu)設(shè)計(jì)原則

②能安全控制大的滲流量（心墻兩側(cè)的無(wú)粘性土的過(guò)渡帶要有較低的滲透性，滲流量可以被降低到一個(gè)可以控制的數(shù)量）保證土壩在產(chǎn)生5～7m的錯(cuò)動(dòng)（距今200年來(lái)活斷層最大位移）時(shí)不致出現(xiàn)大的開(kāi)裂（一般設(shè)計(jì)為有相當(dāng)厚的無(wú)粘性土過(guò)渡帶的多種土質(zhì)壩）上游壩殼下游壩殼防滲心墻地震的工程地質(zhì)研究1.關(guān)于地震指：接近地表面的巖層中彈性波傳播所引起的震動(dòng)中源地震（70～300Km）深源地震（130～700Km）火山地震陷落地震人工誘發(fā)地震淺源地震（0～70Km）按震源深淺分為構(gòu)造地震按成因分為分類(lèi)（最廣、最多、最嚴(yán)重）

2.構(gòu)造地震發(fā)震機(jī)制

產(chǎn)生于板塊邊緣和板塊內(nèi)部活動(dòng)構(gòu)造帶，地殼和上地幔巖石在地球內(nèi)力作用下，產(chǎn)生構(gòu)造變形積蓄應(yīng)變能，一旦達(dá)到巖體強(qiáng)度極限，就會(huì)發(fā)生突然的剪切破裂或沿已有破裂面產(chǎn)生突然錯(cuò)動(dòng)，積蓄的應(yīng)變能就會(huì)以彈性波的形式突然釋放使地殼震動(dòng)而發(fā)生地震。⒊地震波在介質(zhì)內(nèi)部傳播分為·縱波（P波，質(zhì)點(diǎn)振動(dòng)方向與波前進(jìn)方向平行）面波分為體波P-Wave:Thesearecalled'P'forPrimaryWave.Theyaretheonesthattravelfastestandtherebyareusually"felt"first.Theyarebasicallysoundwavesthattravelthrutheearthfromtheepicenterofanearthquake.Physicstypesknowthisasalongitudinalwave.It"shakes"thingsinthesamedirectionittravels.Forexample,ifaP-WaveistravelingWesttoEast,allthethingsintheway,likepeopleandbuildings,willoscillateormovebackandforthintheWest-Eastdirection.Similartoalongstraightlineofbumbercars!Theoneintherearhitsthefirstoneandithitstheoneinfrontofitandsoonandsoon.Aftereachcollision,thecarbouncesbacktoitsoriginalpositiononlytobehitandbumpedforwardagain.Someproperties?FAST!Theycantravelupto20timesthespeedofsoundinair!

Usuallynoticedlike,"Iheardtheearthquakecoming!"ThisisbecauseitIS,indeed,asoundwave.Mostoftenitisn'tnoticedtho.Verylittle,ifany,damage.·橫波（S波，質(zhì)點(diǎn)振動(dòng)方向與波前進(jìn)方向垂直）S-Wave:TheseSecondaryWavesaremuchslowerandmuchmoredestructivethanP-Waves.Theyaretransversewaves.Thismeanstheymaketheearthvibrateperpendicularlytothedirectionofthewavetravel.Notgettingit?Thinkofaropelooselyheldbytwopeople.Onepersonstartsmovinghis/her/itshandupanddownrapidly.Noticethe"wave"intheropegoesfromperson'A'toperson'B'whiletheropeitselfsimplyvibratesupanddown-perpendiculartothedirectionbetweenthetwopeople.Thiswavecausesdamageduetoitsconfiguration.Itcausesbuildingstobethrustupwardfromthegroundthenthegrounddropsoutfromunderitasthewavetravelsby.限于界面附近傳播，由體波到達(dá)地面后激發(fā)的次生波分為·瑞利波(R,在地面滾動(dòng)，質(zhì)點(diǎn)在平行于波傳播方向的垂直平面內(nèi)作橢圓運(yùn)動(dòng),長(zhǎng)軸垂直于地面)RayleighWave:ThisisacombinationPandS-Wave.

It'sanalogoustoanoceanwave.It'sbothlongitudinalANDtransverse.It'shardtoenvision,butlookatthediagrambelow.Thesurface,whilebeingtoldtovibrateforwardandbackwardinthedirectionofthewaveisalsotoldtovibrateupanddownperpendiculartothedirectionofthewave.Gotit?Theresultisthesurfacemovinginaverticalcircularpath-backandforthANDupanddown.TheRayleighwaveisparticularlydamagingbecauseittellsstructurestomoveintwodirectionsatonce.·勒夫波(L，質(zhì)點(diǎn)在水平面內(nèi)垂直于波前進(jìn)方向作水平振動(dòng)作蛇行運(yùn)動(dòng))LoveWave:Notascarysoundingwave,right?Damaging,yes!ThisoneissortaaRayleighWaveonitsside.IttellsthesurfacetomoveforwardandbackwardANDleftandrightatthesametime,sortalikeasurfacecircle.Also,verydamaging.注意·地震記錄圖順序：P——S——L——R·面波對(duì)建筑物的破壞最大（常具有很大振幅，能在建筑物地基之下造成水平剪切）⒋相關(guān)術(shù)語(yǔ)震中:震源在地面的垂直投影點(diǎn)震中距:地面上任一點(diǎn)距震中的距離震源:彈性波的地下發(fā)源地⒌震級(jí)指：一次地震時(shí)震源處釋放能量的大小震級(jí)能量一級(jí)地震能量=2×1013爾格每增大一級(jí)約增30倍一個(gè)7級(jí)地震的能量約合30顆兩萬(wàn)噸級(jí)的原子彈震級(jí)指標(biāo)里氏震級(jí)：距陣中100Km處的標(biāo)準(zhǔn)地震儀所記錄的以微米表示的最大振幅A的對(duì)數(shù)值如：10mm=10000um，則M=lg10000=4實(shí)際里氏震級(jí)：采用修正算法得出

1935年由美國(guó)地震學(xué)家里克特及古騰堡共同制定的里氏地震規(guī)模的主要缺陷在于它與地震源的物理特性沒(méi)有直接的聯(lián)系，且在8.3至8.5級(jí)左右產(chǎn)生飽和，使強(qiáng)度不同的大規(guī)模地震顯示同一數(shù)值。21世紀(jì)初，地震學(xué)者普遍認(rèn)為這些傳統(tǒng)的標(biāo)度已經(jīng)過(guò)時(shí)。1977年美國(guó)加州理工學(xué)院的金森博雄教授提出了地震矩規(guī)模(momentmagnitudescale)，該標(biāo)度能更好地描述地震的物理特性，如地層錯(cuò)動(dòng)的大小和地震之能量。地質(zhì)學(xué)家塞恩·斯坦和埃米爾·歐卡爾認(rèn)為去年年底印度洋大地震地震矩規(guī)模不是開(kāi)始認(rèn)為的9.0級(jí)，而為9.3級(jí)，因?yàn)榈卣鹁氐臉?biāo)度每增加0.3級(jí)，能量就大約增加兩倍。歷史紀(jì)錄中最強(qiáng)烈的地震是1960年5月22日的智利大地震，地震矩規(guī)模9.5級(jí)。日本氣象廳大地震預(yù)警系統(tǒng)⒍地震烈度應(yīng)防止·從地震破壞現(xiàn)象做出烈度的估計(jì)·單憑破壞現(xiàn)象的描述進(jìn)行烈度劃分確定方法——用與震動(dòng)有關(guān)的物理量地面最大位移地面位移加速度地面位移速度與震級(jí)的關(guān)系·震級(jí)一定,震源深度和震中距越小,則烈度越大·M=0.66Io＋0.98·距震中等距離的不同點(diǎn)上的烈度不一定相同地震時(shí)一定地點(diǎn)的地面振動(dòng)強(qiáng)弱的尺度，是指該地點(diǎn)范圍內(nèi)的平均水平而言。指：基本烈度含義的時(shí)代變化特點(diǎn)·不是某一次地震影響所致的烈度·是用統(tǒng)計(jì)學(xué)方法計(jì)算得來(lái)的綜合烈度·“基本”二字是為了與一般使用的烈度意義有別基本烈度指場(chǎng)區(qū)在今后若干年可能遭遇到的最大危險(xiǎn)烈度(廣義的)50～60年代場(chǎng)區(qū)歷史上曾經(jīng)遭受過(guò)的最大烈度為基礎(chǔ)當(dāng)?shù)氐牡刭|(zhì)構(gòu)造特點(diǎn)和地震發(fā)生頻率＋確定特點(diǎn)：沒(méi)有明確的時(shí)間含義70～80年代未來(lái)百年內(nèi)，平均土質(zhì)條件下，場(chǎng)區(qū)可能遭遇的最大地震烈度指：特點(diǎn)：有較明確的時(shí)間含義90年代以后指：50年期限內(nèi)，一般場(chǎng)地土條件下，場(chǎng)區(qū)可能遭遇超越概率為10%的烈度值，即達(dá)到和超過(guò)《中國(guó)地震烈度區(qū)劃圖》上烈度值的概率為10%特點(diǎn)：有較明確的時(shí)間含義和概率含義常用地震烈度術(shù)語(yǔ)場(chǎng)地烈度：指某一地區(qū)或場(chǎng)區(qū)，根據(jù)其地區(qū)的地質(zhì)條件的不同（如巖性、地質(zhì)構(gòu)造、地下水、地形地貌、自然地質(zhì)特征），參照地區(qū)的基本烈度而加以修正的烈度。50年期限內(nèi)，一般場(chǎng)地土條件下，場(chǎng)區(qū)可能遭遇超越概率為10%的烈度值，即達(dá)到和超過(guò)《中國(guó)地震烈度區(qū)劃圖》上烈度值的概率為10%。50年超越概率為10%的風(fēng)險(xiǎn)水平，是目前國(guó)際上一般建筑物普遍采用的抗震設(shè)防標(biāo)準(zhǔn)基本烈度：根據(jù)基本烈度或場(chǎng)地烈度，結(jié)合建筑物所在地的重要性、等級(jí)，以及結(jié)構(gòu)物的特點(diǎn)，為保證建筑物的安全而修正的烈度。設(shè)計(jì)烈度：⒎地震區(qū)劃圖地震動(dòng)峰值加速度指地震動(dòng)過(guò)程中，地表質(zhì)點(diǎn)運(yùn)動(dòng)加速度的最大絕對(duì)值。單位：m/s2

以基本烈度為地震危險(xiǎn)性標(biāo)志服務(wù)于工程建筑抗震工作的一種長(zhǎng)期地震危險(xiǎn)性預(yù)報(bào)圖件指：地震動(dòng)峰值加速度分區(qū)地震基本烈度＜0.05g＜Ⅵ0.05gⅥ0.10gⅦ0.15gⅦ0.20gⅧ0.30gⅧ≥0.40gⅨ編圖及查閱原則②

地質(zhì)條件相同的地區(qū)，地震活動(dòng)性亦可能相同③

90年代后，加入遭遇地震危險(xiǎn)的可能性因素(即發(fā)生概率)④

工作中應(yīng)查閱最新的《中國(guó)地震烈度區(qū)劃圖》①

曾經(jīng)發(fā)生過(guò)地震的地區(qū)，同樣強(qiáng)度的地震還可能重演用途國(guó)家建設(shè)規(guī)劃中小型工程抗震設(shè)計(jì)特點(diǎn)·比例尺?。ㄎ覈?guó)現(xiàn)行同類(lèi)圖為1:300萬(wàn)）·只能提供較大地區(qū)內(nèi)地震危險(xiǎn)度的平均估計(jì)·不能用于預(yù)測(cè)地震破壞作用在較小范圍內(nèi)的變動(dòng)⒏場(chǎng)地地震效應(yīng)指:在地震波的作用下，場(chǎng)地出現(xiàn)的各種破壞作用。分為場(chǎng)地破壞效應(yīng)地面破裂效應(yīng)強(qiáng)烈震動(dòng)效應(yīng)

現(xiàn)象:絕大多數(shù)破壞性地震是由于沿活動(dòng)性斷裂產(chǎn)生突然錯(cuò)動(dòng)而引起.如果震源較淺,斷層錯(cuò)動(dòng)可直達(dá)地表造成地表錯(cuò)斷.它沿一定方向展布于一個(gè)狹長(zhǎng)地帶內(nèi),綿延數(shù)公里至數(shù)百公里,跨越這一斷層的房屋、堤壩、橋梁以及各種管線會(huì)因此破裂而產(chǎn)生嚴(yán)重破壞。TheEmersonfault,oneofthesegmentsthatrupturedintheM7.21992Landers,Calforniaearthquake.(PhotobyKerrySieh,Caltech)地基失效效應(yīng)（砂土液化）現(xiàn)象：如果建筑物地基強(qiáng)度很低或地震動(dòng)加速度很大，就會(huì)導(dǎo)致地基承載力的下降、喪失以致地基的變位、移動(dòng)。砂土液化砂土液化的成因τσn無(wú)水震陷砂土抗剪強(qiáng)度τ＝σn·tgφτ—砂土的抗剪強(qiáng)度σn—砂粒接觸面上的正應(yīng)力pwo飽水無(wú)震砂土抗剪強(qiáng)度τ＝（σn－pwo）·tgφpwo—孔隙水靜水壓力pwo＋Δpw飽水振動(dòng)砂土抗剪強(qiáng)度τ＝[σn－（pwo＋△pw）]·tgφΔpw—振動(dòng)過(guò)程中的剩余孔隙水壓力

粒間無(wú)內(nèi)聚力的松散砂體，主要靠粒間摩擦力維持本身的穩(wěn)定性和承受外力。

當(dāng)受到振動(dòng)時(shí)，粒間剪力使砂粒間產(chǎn)生滑移，改變排列狀態(tài)。如果砂土原處于非緊密排列狀態(tài)，就會(huì)有變?yōu)榫o密排列的趨勢(shì)；如果砂體的孔隙是飽水的，要變緊密就要從孔隙中排出一部分水；如果砂粒很細(xì)，整個(gè)砂體的滲透性不良，瞬時(shí)振動(dòng)變形須從孔隙中排出的水來(lái)不及排出砂體以外，結(jié)果必然使砂體中孔隙水壓力上升，砂粒間有效正應(yīng)力就隨之降低。

當(dāng)孔隙水壓力上升到使砂粒間有效正應(yīng)力為零時(shí)，砂粒就會(huì)懸浮于水中，砂體也就完全喪失了承載力，這就是砂土液化。導(dǎo)致砂土液化的振動(dòng)機(jī)械振動(dòng)(限于個(gè)別地基或個(gè)別場(chǎng)地范圍)地震(區(qū)域性的，面積可達(dá)數(shù)千平方公里)

自灤河口以西直至寧河一帶,數(shù)千平方公里范圍內(nèi)到處噴水冒砂,十幾萬(wàn)畝農(nóng)田為砂土所覆蓋,十幾萬(wàn)口機(jī)井為砂所淤塞,不少公路鐵路大橋由于強(qiáng)烈沉降而被毀,許多工業(yè)民用建筑物受到破壞.其它如75年的海城地震、64年的阿拉斯加地震等都引起過(guò)較大區(qū)域的砂土液化.砂土液化的危害涌砂：掩蓋農(nóng)田，嚴(yán)重?fù)p害農(nóng)業(yè)灌溉設(shè)施地基失效：隨粒間有效正應(yīng)力降低，地基土層的承載力也迅速下降，直至砂體呈懸浮狀態(tài)時(shí)地基的承載能力完全喪失。地面沉降和地面塌陷：變密而沉降，涌砂而塌陷由于下伏砂層或敏感粘土層震動(dòng)液化和流動(dòng)，可引起大規(guī)?；隆；簠^(qū)域性砂土地震液化的形成條件砂土特性結(jié)構(gòu)愈松散，越易液化粉(0.075≥d＞0.005)、細(xì)(0.25≥d＞0.075)砂體最易液化粘粒含量少、粒徑愈均勻，愈有利于液化砂體埋藏條件直接出露在地表的飽水砂層最易于液化地下水埋深愈淺，非液化蓋層愈薄，愈易液化地震特性地震愈強(qiáng)、加速度愈大，則愈容易引起砂土液化地震持續(xù)時(shí)間愈長(zhǎng)，愈易引起液化砂土液化防護(hù)措施良好場(chǎng)地的選擇表層非液化蓋層厚度大地下水埋深大人工改良地基增加蓋重?fù)Q土（適于地表處理）改善飽水砂層的密實(shí)程度選擇適宜的基礎(chǔ)形式筏片基礎(chǔ)（層數(shù)較少時(shí)）較深的支撐樁基或管柱樁基

斜坡破壞效應(yīng)臺(tái)灣921地震山崩的土石阻塞清水溪流路，形成堰塞湖

最新的堰塞湖于2000年4月因地震誘發(fā)的西藏易貢藏布大滑坡引起。

LakeSarez(top),deepinthePamirmountainsofTajikistan,wascreated90yearsagowhenastrongearthquaketriggeredamassivelandslidethat,inturn,becameahugedamalongtheMurghobRiver,nowcalledtheUsoiDam.6月9日17時(shí)，從空中看到的堰塞湖泄洪渠水流越來(lái)越急。新華社記者李剛攝

6月14日，日本宮城縣栗原市的公路在地震中因塌方而損毀。5.12汶川大地震中山體垮塌阻斷了都江堰至汶川的交通通路新北川中學(xué)巖崩906人死亡！水庫(kù)誘發(fā)地震⒈水庫(kù)誘發(fā)地震的共同特點(diǎn)震中密集于庫(kù)壩附近水庫(kù)最大水深區(qū)庫(kù)區(qū)及附近斷裂帶震源極淺（4～7Km，導(dǎo)致面波強(qiáng)，0點(diǎn)幾級(jí)就有震感，3

級(jí)就可造成破壞）地震活動(dòng)峰值在時(shí)間上均較水位或庫(kù)容峰值有所滯后⒉水庫(kù)誘發(fā)地震的誘發(fā)機(jī)制⑴不是水庫(kù)荷載直接造成的⑵水庫(kù)蓄水對(duì)庫(kù)底巖體的各種效應(yīng)物理化學(xué)效應(yīng)使巖體斷裂面及其充填物軟化、泥化,而降低其抗剪強(qiáng)度硬石膏水化膨脹（大規(guī)模、突然膨脹的可能性極?。?yīng)力腐蝕（硅氧分子水化后會(huì)使破壞時(shí)間顯著縮短）水庫(kù)荷載效應(yīng)荷載產(chǎn)生巖體內(nèi)的附加應(yīng)力，惡化斷裂面的應(yīng)力條件（尤其是大水庫(kù)）當(dāng)庫(kù)底巖體兩側(cè)有深大陡立斷裂時(shí)該效應(yīng)更加明顯空隙水壓力效應(yīng)原抗剪強(qiáng)度τ=c+σntgфσnτ=c+σntgф現(xiàn)抗剪強(qiáng)度τ=c+(σn-Pw)tgф(考慮空隙水壓力后)Pwσnτ=c+(σn-Pw)tgф即：透水裂隙庫(kù)水滲入提高空隙水壓力降低裂隙面上正應(yīng)力降低抗剪強(qiáng)度⒊

水庫(kù)誘發(fā)地震的地質(zhì)條件轉(zhuǎn)換斷層及大的平移斷層處可能性較大（美國(guó)的圣安德烈斯斷層）相當(dāng)高的天然地應(yīng)力及中等到較高的應(yīng)變積累速度明顯的新構(gòu)造活動(dòng)跡象（是水庫(kù)誘發(fā)地震的必要條件）較高的巖體強(qiáng)度和完整性（利于積蓄應(yīng)變能）原始地下水位低、庫(kù)水入滲通道發(fā)育（如喀斯特地貌發(fā)育區(qū)等）地?zé)崃鞲撸ㄊ且话闼畮?kù)地震震例具有的條件，如火山、溫泉）

三峽水庫(kù)建成蓄水后是否會(huì)誘發(fā)地震？有關(guān)專(zhuān)家認(rèn)為，有可能局部出現(xiàn)水庫(kù)誘發(fā)地震的現(xiàn)象發(fā)生。到目前為止，全世界共發(fā)生水庫(kù)誘發(fā)地震約70起至80起，占世界水庫(kù)的2‰至3‰。但隨著大壩高度的增加，發(fā)生水庫(kù)誘發(fā)地震的比例也相應(yīng)增加，壩高超過(guò)200米的水庫(kù)（三峽壩高為185米），發(fā)生誘發(fā)地震的實(shí)際比率為34％?，F(xiàn)在，全球記錄的最大的兩次水庫(kù)誘發(fā)地震發(fā)生在印度的柯依納水庫(kù)（6.5級(jí)）和我國(guó)的新豐江水庫(kù)（6.1級(jí)）。專(zhuān)家說(shuō)，三峽水庫(kù)大壩是建立在一個(gè)80平方公里完整的花崗石上，這從某種程度上減少了蓄水后誘發(fā)地震的幾率。而有可能誘發(fā)地震的巫山和巴東地區(qū)，目前也已做好了治理與防護(hù)工作。此外，一個(gè)由全球定位系統(tǒng)、精密激光測(cè)距等先進(jìn)技術(shù)組成的地殼形變監(jiān)測(cè)網(wǎng)、誘發(fā)地震檢測(cè)總站以及采用當(dāng)今先進(jìn)成熟的數(shù)字遙測(cè)技術(shù)的地震臺(tái)網(wǎng)也已投入運(yùn)轉(zhuǎn)。EARTHQUAKESANDRESERVOIRSFactsAboutReservoirs

Herearesomebasicfactsaboutreservoirs:1.Reservoirsarebuiltinvalleys.2.Valleysareareasthathavebeenerodedovertime.3.Valleysindicatesthatupliftbyfaulting(earthquakes)hasoccurredintheregion.4.Thereforewhenwaterisplacedinavalleyforareservoir,itisonornearafaultline.HowReservoirsImpactFaultsTherearetwowaysthatearthquakescanoccurwhenareservoirisbuiltnear/onanearthquakefault.

First,whenwaterisaddedtoavalleyandon/nearafaultlinethereisadditionalweighttotheearth'ssurface--thisinturnchangesthestressofthefault.

Whenwaterisaddedtheamountofstressincreasesonthefaultline.

Second,andslightlymoretechnical,thewaterchangestheamountofspace(porosity)oftheunderlyingsoil.

Whenthisoccursthegroundbecomessaturatedandmoreunstable.

ThisphenomenonisknownasReservoirInducedSeismicityorR.I.S.WhenwilltheEarthquakeHappen?Accordingtoexperts,itismostlikelythatanearthquakewilloccuralmostimmediatelyafterfillingthereservoir.

Ifthereisadelayofafewyearsitwouldbebecauseofthesaturationofthesoiltooklonger...meaningiftherockwasnotveryporous,itwouldtakelongertobecomesaturatedandthereforelongertochangethestabilityofthesurroundingsoil.RecipeforanEarthquakeInordertotriggeranearthquakethefollowingwilloccur:⑴Areservoirbuilton/nearanactivefaultcancauseeither:

Thefaultlinetobestressedbytheweightofthewater

-or-B.

Theground'sstabilitychangeswhenwaterisaddedtothesurface.⑵Thepressurebecomestoogreatorthegroundtoosaturatedandthefaultreleasesproducinganearthquake.⑶Increasedgroundwaterporepressuredecreasestheeffectivestrengthoftherockunderthereservoir.WaterPorePressureGroundwaterplaysalargepartinearthquakeactivity.FluidinjectionintowellsinUSA,Japanandelsewherehastriggeredsmallearthquakes.Waterporepressurereducesthenormalstresswithinarockwhilenotchangingtheshearstress.Underanycircumstances,anincreaseinwaterporepressuremeansthatafailureismorelikely.Thecriticalvalueofshearingstressmaybemadearbitrarilylowbyincreasingtheporepressure.Porepressurecanincreaseintwoways:?Duetothedecreaseinporevolumecausedbycompactionundertheweightofthereservoir.Thisoccurswhilethereservoirisbeingfilled.?Duetodiffusionofreservoirwaterthroughpermeablerockunderthereservoir.Therateofflowdependsonthepermeabilityoftherock,sothiseffectisnotinstantaneous.Theincreaseinporepressuretakesmoretimedependingonthedistancefromthereservoir.Itmaytakeyearsfortheporepressuretoincreaseatdepthsofkilometresbeneathareservoir.DurationofReservoirInducedSeismicityReservoirinducedseismicityisatransitoryphenomenonwhichwilloccureitherimmediatelyafterfillingofthereservoir,orafteradelayofafewyears.Ifthereisadelay,thisdependsonthepermeabilityoftherockbeneaththereservoir.Oncestressandporepressurefieldshavestabilisedatnewvalues,reservoirinducedseismicitywillcease.Earthquakehazardwillthenreverttosimilarlevelsthatwouldhaveexistedifthereservoirhadnotbeenfilled.Evenforthosereservoirsthatshowacorrelationbetweenearthquakeactivityandwaterlevel,reservoirinducedseismicitydoesnotcontinueindefinitelyasitislimitedbytheavailabletectonicenergy.DepthofReservoirInducedSeismicityDepthsofreservoirinducedearthquakes,especiallythoseoccurringimmediatelyafterfillingofthereservoir,arenormallyveryshallow.Ifdetailedseismographcoverageisavailable,thendepthswithinonetothreekilometresofthesurfacearecommon.Inducedearthquakesatreservoirsthathaveexperienceddelayedtriggeringmaybemuchdeeper,perhapsasdeepastentotwentykilometres.Thesemayoccurtentotwentyyearsafterfillingofthereservoir.PredictionofReservoirInducedSeismicityItisnoteasytopredictwhetheranewreservoirwillexperiencereservoirinducedseismicity,becausethetwomostimportantfactors-thestateofstressandtherockstrengthatearthquakedepths-cannotbemeasureddirectly.Thisisthesamereasonwhypredictionofnormal(non-induced)earthquakesisnormallyunsuccessful.PLACESSCIENTISTSBELIEVERISHASALREADYOCCURREDYear:

Location:Earthquake

Produced:1967

Koyna,IndiaM6.71962

Xinfengjian,ChinaM6.21971

Nurek,TadjikistanM4.61973

Warragamba,NSWAustraliaM5.51978

Monticello,SouthCarolinaM4.11981

Aswan,EgyptM5.31993

Killari,SWIndiaM6.11996

Thomson,VictoriaAustraliaM5.1M=MagnitudeSincegeologistsknowthattheWhittierextensionoftheElsinoreFaultisanactivefaultlineandthatwaterincreasesthestressonafaultand/orchangesthestabilityofthegroundbeneaththereservoir,

thedangerposed

bytheIndustryreservoirsisreal.

ShouldanearthquakeoccurontheWhittierFaultandshouldthedambreak

the275,000acrefeetofwater

wouldinundatelargeportionsoftheCityofBreaandFullerton,includingBreaJuniorHighandthedowntown.MorespecificallythoselivingalongBreaCanyonRoadandBreaBlvd.,willbeinundatedwithwaterminutesafteralargeearthquake.

Thisisadisasterthatshouldbeavoidedentirely.

Shouldasaddledambreak,someofwhichareproposedtobeashighas120',thereisnodoubtneighborhoodsinDiamondBarwillbefloodedaswell.WHATDOESTHISMEANFORINDUSTRY'SPLANNEDRESERVOIR?印度洋地震后海底山脊倒塌形成山崩地段中間凹陷部分為印度洋大地震給海床烙上的“傷疤”近日英國(guó)科學(xué)家公布了去年年底印度洋大地震發(fā)生后，受板塊構(gòu)造沖撞而發(fā)生變化的震中地區(qū)海床的首批圖片。這是人類(lèi)歷史上大規(guī)模地震爆發(fā)后，海床首次被迅速觀察得到的結(jié)果。圖片顯示，受地震影響，印度洋海底山脊已倒塌，并形成數(shù)公里寬的山崩地段。據(jù)最新一期的《自然》雜志文章報(bào)道，英國(guó)專(zhuān)家利用高清晰度的多束激光聲吶對(duì)海底進(jìn)行了掃描，這些圖片顯示，受地震影響，印度洋海底中高達(dá)1500千米的山脊已出現(xiàn)了巨大的倒塌，并形成數(shù)公里寬的山崩地段?？茖W(xué)家初步評(píng)估，地震發(fā)生時(shí)，印度和緬甸兩塊板塊構(gòu)造突然運(yùn)動(dòng)相碰時(shí)，印度板塊構(gòu)造被向下擠壓，造成海床隆起一道山脊，海水因此向上涌出，結(jié)果引發(fā)了去年12月26日發(fā)生的東南亞大海嘯。

這兩張2004年12月30日發(fā)布的衛(wèi)星圖片顯示的是印度尼西亞亞齊省首府班達(dá)亞齊海濱地區(qū)受海嘯襲擊前后的情形。其中，上圖拍攝于6月23日。上圖拍攝于12月28日。SoilImprovementTechniquesThemaingoalofmostsoilimprovementtechniquesusedforreducingliquefactionhazardsistoavoidlargeincreasesinporewaterpressureduringearthquakeshaking.Thiscanbeachievedbydensificationofthesoiland/orimprovementofitsdrainagecapacity.VibroflotationVibroflotationinvolvestheuseofavibratingprobethatcanpenetrategranularsoiltodepthsofover100feet.Thevibrationsoftheprobecausethegrainstructuretocollapsetherebydensifyingthesoilsurroundingtheprobe.Totreatanareaofpotentiallyliquefiablesoil,thevibroflotisraisedandloweredinagridpattern.VibroReplacement(right,HB)isacombinationofvibroflotationwithagravelbackfillresultinginstonecolumns,whichnotonlyincreasestheamountofdensificton,butprovidesadegreeofreinforcementandapotentiallyeffectivemeansofdrainage.DynamicCompactionDensifictionbydynamiccompactionisperformedbydroppingaheavyweightofsteelorconcreteinagridpatternfromheightsof30to100ft.Itprovidesaneconomicalwayofimprovingsoilformitigationofliquefactionhazards.Localliquefactioncanbeinitiatedbeneaththedroppointmakingiteasierforthesandgrainstodensify.Whentheexcessporewaterpressurefromthedynamicloadingdissipates,additionaldensificationoccurs.Asillustratedinthephotograph,however,theprocessissomewhatinvasive;thesurfaceofthesoilmayrequireshallowcompactionwithpossibleadditionofgranularfillfollowingdynamiccompaction.CompactionPiles

Compactiongroutingisatechniquewherebyaslow-flowingwater/sand/cementmixisinjectedunderpressureintoagranularsoil.Thegroutformsabulbthatdisplacesandhencedensifiesthesurroundingsoil(right,HB).Compactiongrouting