перевод на русский пож What causes earthquakes?
01.1.r o1d earth stretc hes and deforms its rock layers at a rate too fast for themselves
quitietly.
Scientists are not su/e whether the eart his growing
bigger and stretching crustàlrocks,orshrinking
to wrinkle them like dried appleskins.In any
cmse,therearenian#r:asonsforthesqueezingand
tw isting ofthe rocks thatcause such trouble.
Chem icaland radioactivereactionsm elttheinteriorm
aterialscausing pressureagainsttheoverlying
rocks.M ostim portantm ay be the w eightof eaG h
m aterialm oved from placeto placeby the ruslting
waters of rivers.This happens slow ly,butthere is
a11thetimeintheworld,mldafterm illionsofyears
theweightof m aterialbecom esvery great. '
Breaking takes place along zones of weakness
called faults.Oneside of the rock m ovespastthe
other,sidew aysor up ordown,sliding and grinding
along the fault untilthe tension is released.
Therock then com esto restin itsnew position,to
stay untiltension builds up again.The following
two exam ples m ay dem onstrate the disaster.
11
On A pril18, 1906,one of the greatest shocks
in A m erican history struck San Francisco, It
150
happened at 5:12 on a weekday m orning w hen
the downtow n business districtw as deserted and
streets were empty.The death tollwas between
452 and 498 persons.
A ctually the quake buckled and rolled over
a 200-m i1e stretch of the San A ndreas fault.
Altogether,âtleast 700 persons were killed.
RqnFrancisco'sdnmagewasestimatedat$400million
ata tim eofs-centbeerand ls-centprim ebeef.
W hat if a quake of sim ilar strength struck at
noon on a week-day? Itis a chilling possibility.
Can citieseventually bebuiltso they're quakeproof?
Yes,say the experts.
Earthquakednmagetostructureshasbeenpainstakingly
studied during thepasthalfcentury.
RThere is no reason for a fifty-storey building
to be less safe than a five-storey building if it is
constructed properlyy''saysDr.George W .H ousner,Caltech
professorofcivilengineering.Finally,
willit eventually be possible to predict quakes?
An internationalstudy is now in progress in an
effort to answer this question.
GW ith increasing inform ation about the eazth
m ovem ents a1lover the world,''Dr.Benioff says,
d w ould tellus when and where the breaking point
hasbeen reached-''
It can't be concluded as yet that earthqultktls
com ein cyclesbecausethey haven'tbeen observtltl
orrecorded long enough.III r 3. The possibility ofconstructing quake-proof
<'The likelihood of a major er thquake hitting '
,, a.
itj gapanese ' 4' Pho Possibility to forecastearthquakes.
Tokyo is now greater than ever, s
geographer Takam asa Nakuno.On average severe ' r
, . - 3aaaxee 9.l'Ipoql/'ral're Iï rzepecltam Hq'e
earthquakes(aboutVIIIon theModified Mercali
SCaleOr6.5ontheRichterScale)alfecttheTokyo TORCT'
areaabout10timesacentury.Thelastcomparable Oneofm;favoriteplacesistheHindersRanges.
quake wasin 1929,sothenextisreckoned tobe Thisrtzggedandbeautifulchainofmountains,strdch.
welloverdue.The last destructive earthquake to ing from theSpencerGulfregionnorth towardsLake
affect Tokyo occurred in 1923 when 60,000 lives Eyre,is wellknown to South A ustralians,w ho cart
wereclaim ed and 370,000 housesweredestroyed. easilygettherein aday'sdrivefrom Adelaide.
Tokyo has changed considerably since 1923. y Itislessvisited bytravellersfrom otherstates
The urban area has expanded and the density of butIam pleased to seetravelwritersR on and Viv
wooden houses has increased. Nakuno sees new M oon have written a book on this area.
danger areas in the subways and underground ' The Flinders ss a long range,stretching from
J
shopping com plexes. the salubriousvillageofCrystalBrook to the arid
The Tokyo M etropolitan governm ent stillsees plalnsofM ountH opeless.And ithasbeen around
fireasthem ajorhazard resulting from an earth- a long time.Its geolo-gy reveals nearly half the
quake and its counter-m easures are designed to history ofour planet.
dealwith a largenumberofsim ultaneousfireson M ysteriouscarvingsin therocksrevealhum an
intlependent sites.A centralpart of their earth- habitation ofat least 15,000 years,
quakespolicy istodesignateopen spacesforevacu- ThefirstEuropean toseetherangeswasM atthew
ation and build fire-proofhighrise buildings.