EveryonehasheardoftheSanAndreasfault，whichconstantlythreatensCaliforniaandtheWestCoastwithearth-quakes.ButhowmanypeopleknowabouttheequallyseriousNewMadridfaultinMissouri.&rsquo

BetweenDecemberof1811andFebruaryof1812，threemajorearthquakesoccurred，allcenteredaroundthetownofNewMadrid，Missouri，ontheMississippiRiver.Propertydamagewassevere.

Buildingsintheareawerealmostdestoyed.Wholeforestsfellatonce，andhugecracksopenedintheground，allowingsmellofsulfurtofilterupward.

TheMississippiRiveritselfcompletelychangedcharacter，developingsuddenrapidsandwhirlpools.Severaltimesitchangeditscourse，andonce，accordingtosomeobservers，itactuallyappearedtorunbackwards.FewpeoplewerekilledintheNewMadridearthquakes，probablysimplybecausefewpeoplelivedintheareain1811buttheseverityoftheearth-quakesareshownbythefactthattheshockwavesrangbellsinchurchtowersinCharleston，SouthCarolina，onthecoast.BuildingsshookinNewYorkCity，andclockswerestoppedinWashingtonD.C.ScientistsnowknowthatAmerica&rsquostwomajorfaultsareessentiallydifferent.TheSanAndreasisahorizontalboundarybetweentwomajorlandmassesthatareslowlymovinginoppositedirections.Californiaearthquakesresultwhenthemovementofthesetwomassessuddenlylurchesforward.

TheNewMadridfault，ontheotherhand，isaverticalfaultatsomepoint，possiblyhundredsofmillionsofyearsago，rockwaspusheduptowardthesurface，probablybyvolcanoesunderthesurface.Suddenly，thevolcanoescooledandtherockcollapsed，leavinghugecracks.Evennow&rsquo，therockcontinuestosettledownwards，andsuddensinkingmotionstriggerearthquakesintheregion.Thefaultitself，alargecrackinthislayerofrock，withdozensofothercracksthatsplitofffromit，extendsfromnortheastArkansasthroughMissouriandintosouthernIllinois.

ScientistswhohavestudiedtheNewMadridfaultsaytherehavebeennumeroussmallerquakesintheareasince1811thesesmallerquakesindicatethatlargeronesareprobablycoming，butritescientistssaytheyhavenomethodofpredictingwhenalargeearthquakewilloccur.Asusedinthefifthsentenceofthefourthparagraph，theword"essentially"means（）

A.greatly

B.extremely

C.basically

D.necessarily

1.Thispassageismainlyabout（）.

A.theNewMadridfaultB.theSanAndreas

C.thecausesoffaultsD.currentscientificknowledgeaboutfaults

2.Thispassageimpliesthat（）_.

A.horizontalfaultsaremoredangerousthanverticalfaults

B.verticalfaultsaremoredangerousthanhorizontalfaults

C.morepeoplewoulddieifthe1811NewMadridearthquakeshappenedtoday

D.thevolcanoesthatcausedtheNewMadridfaultarestillalive.

3.Theunderlinedword"vertical"mostprobablymeans（）_.

A.movingstraightupB.terriblychanging

C.breakingsuddenlyD.extendinglargely

正确答案：C

答案解析：[试题分析]词义理解题。

[详细解答]作者在提到圣安德里亚断层时用到了horizontal这个词，而用vertical来形容新马德里断层，而且，通过转折短语ontheotherhand，我们显然可以推断，essentially近义于basically，故答案为C。

答案:1-3：ABA