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Mostearthquakesoccurwithintheupper15milesoftheearth'ssurface.Butearthquakescananddooccuratalldepthstoabout460miles.Theirnumberdecreasesasthedepthincreases.Atabout460milesoneearthquakeoccursonlyeveryfewyears.Nearthesurfaceearthquakesmayrunashighas100inamonth,buttheyearlyaveragedoesnotvarymuch.Incomparisonwiththetotalnumberofearthquakeseachyear,thenumberofdisastrousearthquakesisverysmall.Theextentofthedisasterinanearthquakedependsonmanyfactors.Ifyoucarefullybuildatoyhousewithanerectset,itwillstillstandnomatterhowmuchyoushakethetable.Butifyoubuildatoyhousewithapackofcards,aslightshakeofthetablewillmakeitfall.AnearthquakeinAgadir,Morocco,wasnotstrongenoughtoberecordedondistantinstruments,butitcompletelydestroyedthecity.Manystrongerearthquakeshavedonecomparativelylittledamage.Ifabuildingiswellconstructedandbuiltonsolidground,itwillresistanearthquake.Mostdeathsinearthquakeshavebeenduetofaultybuildingconstructionorpoorbuildingsites.Athirdandveryseriousfactorispanic.Whenpeoplerushoutintonarrowstreets,moredeathswillresult.TheUnitedNationshasplayedanimportantpartinreducingthedamagedonebyearthquakes.Ithassentateamofexpertstoallcountriesknowntobeaffectedbyearthquakes.Workingwithlocalgeologistsandengineers,theexpertshavestudiedthenatureofthegroundandthetypeofmostpracticalbuildingcodeforthelocalarea.Iffollowed,thesesuggestionswillmakedisastrousearthquakesalmostathingofthepast.Thereisonetypeofearthquakedisasterthatlittlecanbedoneabout.Thisisthedisastercausedbyseismicseawaves,ortsunamis.(Theseareoftencalledtidalwaves,butthenameisincorrect.Theyhavenothingtodowithtides.)Incertainareas,earthquakestakeplacebeneaththesea.Thesesubmarineearthquakessometimesgiverisetoseismicseawaves.Thewavesarenotnoticeableoutatseabecauseoftheirlongwavelength.Butwhentheyrollintoharbors,theypileupintowallsofwater6to60feethigh.TheJapanesecallthemtsunamis,meaningharborwaves,becausetheyreachasizableheightonlyinharbors.Tsunamistravelfairlyslowly,atspeedsupto500milesanhour.Anadequatewarningsystemisinusetowarnallshoreslikelytobereachedbythewaves.Butthisonlyenablespeopletoleavethethreatenedshoresforhigherground.Thereisnowaytostoptheoncomingwave.1.WhichofthefollowingCANNOTbeconcludedfromthepassage?A.Thenumberofearthquakesiscloselyrelatedtodepth.B.Roughlythesamenumberofearthquakesoccureachyear.C.Earthquakesareimpossibleatdepthsover460miles.D.Earthquakesaremostlikelytooccurnearthesurfaces.A.faultybuildingconstructionB.anearthquake'sstrengthC.widespreadpanicinearthquakesD.ineffectiveinstrumentsA.constructstrongbuildingsB.putforwardproposalsC.detectdisastrousearthquakesD.monitorearthquakes4.ThesignificanA.noticethemoutatseaB.findwaystostopthemC.bewarnedearlyenoughD.developwarningsystems参考答案：1~4CABC1~5ADBDC6~10ADBCA