更新时间：2025-08-07 14:28:34
anearthquakeisashakingofthegroundcausedbythesuddenbreakingandshiftingoflargesectionsofearthsrockyoutershell.earthquakesareamongthemostpowerfuleventsonearth,andtheirresultscanbeterrifying.asevereearthquakemayreleaseenergy10,000timesasgreatasthatofthefirstatomicbomb.rockmovementsduringanearthquakecanmakeriverschangetheircourse.earthquakescantriggerlandslidesthatcausegreatdamageandlossoflife.largeearthquakesbeneaththeoceancancreateaseriesofhuge,destructivewavescalledtsunamis(pronouncedtsoonahmeez)thatfloodcoastsformanymiles.
earthquakesalmostneverkillpeopledirectly.instead,manydeathsandinjuriesinearthquakesresultfromfallingobjectsandthecollapseofbuildings,bridges,andotherstructures.fireresultingfrombrokengasorpowerlinesisanothermajordangerduringaquake.spillsofhazardouschemicalsarealsoaconcernduringanearthquake.
theforceofanearthquakedependsonhowmuchrockbreaksandhowfaritshifts.powerfulearthquakescanshakefirmgroundviolentlyforgreatdistances.duringminorearthquakes,thevibrationmaybenogreaterthanthevibrationcausedbyapassingtruck.
onaverage,apowerfulearthquakeoccurslessthanonceeverytwoyears.atleast40moderateearthquakescausedamagesomewhereintheworldeachyear.about40,000to50,000smallearthquakes--largeenoughtobefeltbutnotdamaging--occurannually.
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