Earthquake Hazards Responses

8/14/2019 Earthquake Hazards Responses

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4. EARTHQUAKE HAZARD5 AND RESPONsES I

q) Mqin chqrocteristicsAn earthqudke is o shoking of fhe ground, usuolly coused by rocks rupturrngunder StressSeisnology is the study of eorthquokes.Focus (olso known os 'Hypocenier'). The locqtion wifhin the crust where rupiare of rocks initiotes, ond ihus,where energy is fist releosed. Shollow-focus eorthquokes - focol depth of less thqn 70km. Intertnediole - focus edrthquokes focol depth of belween 70 to 300km. Deep-focus eorfhquokes - locol depth greoter thon 300km

-t

Epicentre. Poinf on the eorth's surface thatis direcfly qbove the focLls

Figure 66. Focus ond epicefltre of 6nEorthgucke

Rock5 fupturing from greot stress genetole seisnic woves thot rodiole fromfhe eorthquoke focus in oll directions The shoking ond destruction re3ultingfrom earthqudkes ore coused by two differenl lypes of seismic wovesr bodywoves ond surfoce woves. The woveS thof orrived of o setsmogroph oremonito.ed ond diffetentaoted to locoie the epicenlre of on eorthquoke.

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. i) Body Woves I ; ') Sucfoce Wovei :P e,r'oves, 5 Woves

i) Body wovesL woves, Royleigh woves

{ Irovel frotn fhe eorthquoke focus underground to the surfoce{ Two iypes: primory woves (P woves) ond secondory woves (S-woves){ The velocities of P-woves ond S-woves are dete t\ined by the density ondelosiicity of the moteriols through which they lrovelI Seismac woves lrovel more slowly through denser rocks but nore ropjdly throughrocks with gredter eloslicityP wdves (PrimoryFirsi woves felt in

l1/aves)qn eorlhq{-roke.

5 - wa ves(Secondary 14aves)

speedlL Th's ,s lhe foslesiwoves (6 8km per rec

speed:{ Siouier thon o P rlove4 5kn pe. sec) and conihrough sol,d rock

'l Po5s throLrgh theand doqn 1otrcn

(obout 3 5

eorth wtth on up

L Are cohpressionalshoke the eorth

is iyp,col)

ke shzar waves thot noue themoteriol perpendiculor fo thed,rection of fr(lvel, iherebyprodrcrng sheor siresses rn ihemofeflol they move throuqht The moteridl through whrch P-wovesIftvel is expanded and coapressedos ihe wdve 6rove through it ond

retLrrns to its origrnol siz ond shopeafie. lhe wsve pdsses by

l

Second wove felt in on eorlhquoke

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+

Surfoce wovesProduced in ih 9.ound by ihe lronsformotion of some body woves once they teachthe svf oce.Trovel olong the surfoce of the eqrth, cousing rocks ond soil to be disploced insuch o woy thol the ground ripples or undulotesI Slower thon body wovesa Tu./o types: Royleigh woves (R waves) ond Love woves (L woves)

P"yt";gh *";;; L - wavesNomed after A E.H. Love. o Britishmdthemoticion who worked out fhemothernolicol model for this kind ofwove in l9l1-sp."d, Jut."r, qlower lhan I -6n'p\ I Foster surid. e wovel ovement: ). u^,,.^-^,ftenr: i Movemeni:r Behove |ke worer woves in wh,ch i .,1. Motion is s,m,io. to o S wdve, burrhey couse on ell,pracol (rotaring) the ,nd,v,duot po.t,.ts of ihenrot,on ,n the motzrrol whrch rhey j mdie ot onty rnove bock and forih rnmove fh.ough d horizonldt plone perpendrcutdr tofhe direci,on of wave iroveleffect:r Most of rheeorihq!oke rs shokrng felt froin ondue to the Royle,gh This iype to b!ildrng

Eftect.domo9,n9wove. which con be much io.ger tho^

Why ore seismic woves imporfont?{ The vorious seismic w6ves travel ot di(ferenl speeds ond thereforz orrive ot cse;snogroph of different times+ The epicentre of ony eorthquoke con be determined by using o time distqnce grophond knowing the orrivol times of the P,wcves ond s-wqves


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Divergenf Plote Boundqries (ond Hof spois):The remoining 5% of eorthquokesoccur in lhe inieriors of plotes ond olong mid-oceonic radges.Due lo the differences in the noture of fhe confoct ot different fypes of ploieboundories, seisnic events occor at different focus depths qnd diffe.ent powerlevels for eoch type.Eorthquokes generoted olong divergent or tronsforrn plqte boundqries ore usuollyshollow focus. Shollow-focus eorthguokes ore olso generoled ot conveagenl plateboundories ol the poinl wheae subducfion occurs cnd below the oceon tTenches.Mo.e thon 757" of eorlhgtokes oround the world occur shollower thon 6okrn.

Almost oll internediqte ond deep-focus eo.thquqkes occur qlong the Benio(fZone where subduction occurs ot convergent plote boundories within the crrcum-Pocific belt ( Fig 69)

l'-;,

+

O-x:rnl: Lth.}lrh.e OErnir o' Coniicnt l

Fig 69: Shollow focus. infermdiate focusdispority in depth of earthquoke ond deep focus eorthgudkes. Note thefoci or different boundories.

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eqrthquqks: Mqqnifude Vs Intensi.aL Geologists meosure the sfrength of dn eorthquoke in 2 different woys:

> tvlqgniiud - guantitative meosurement of fhe omount of energy releosedby on eorthqloke {'lsihg the Richfer scole.> Intehsity - gualitdtive ossessmeht of the kinds of dornoge done by oneorthguoke using the Mercolla scole.

i){+

Eoch rnethod provides importont doto obout eorthqdokes ond theit etfects whachcon be used to prepore for future eorthquokes/\leoslring Mqgnitude: Richler scole ( Fig 7O)

Developed 14 Charles F. Richter in 1935Used to meqsure moghitude or the fofol omoln? of energy teleosed by aaeorlhguoke ot its solrce.

I Involves meosuring the height of the seismic woves on o seismogron:> The seishogroph. times ond rcords th inconing woves_/ A seishogrdph hor two components:. setsnonefer to :;ense the qround vibrations and a recordnq dence. he chatt poper utth the trocing is known as the seismogram. Mode(n seismogrophs use more sophisticoted rccatding techniqles. One modelrecords electric srgncls from ihe seish\ogroph onlo mognetic tope. providing omore

flexible woy to onalyz the doid by computer processingI Richter Scole is on open ended scale with volues beginning qt 1, ie there is nouppe. limit{ Scole is logo.ithrnic : An eqrthquoke of mqgnifode 4 couses 10 times moreground motion os one of mqgnitude 3 ond 1OO limes mo.e os mognilude 2

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Edrth+roke Effects

lAbo(i 8,OOO per

About 1,OOO per

l Less thon 2o

2.O,2.9

Micro@rthqsdkes. not f eli-

Generolly not feh.6rt rccorded.

30-39 Oftea felr.but rorely .ouses donoge 49,oOO Fet yeor(esi )

6 ,2OO pet ye6t(esi.)ight

5irong

40,4 9 Noticeoble shdking of indoor rtelns,.otilinq noisessi9n,f icont ddmoge unlakely

ccn couse tno.lor domcge to poo.ly consr.scred bqildings5A-5.9 over smollregions. Al host slighr damoge ro well- 8O0 per yo.d"


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osu. ng nte s ty: /r4odified /vlercolli Infensify Scole ( Fig Z1)'I Scole used to clossify the infensity of qn eorihguoke bosed on fhe domcge coused( ie: 6lqn6t. to hLtmon st.uctures) ond iis effects per ceived 6y people.'t A number from I fo XII is ossigned to dn eorlhquoke.L Surfoce effects of on eorthquoke vories depending on fociors like:

> Geological cohditions: Certoin soil types ( re: silf, olluvium) con intenjify serslnicshaking, ledding to greater domage to structures> Quality of construction: B$ldings thoi ore nol reinforced and that do nol hoveiheir foundofions set rnfo hord rock. wrlt be morevulneroble to collopse during an eorthguoke> Populolion density: Areos wath higher populqtion density will susrorn greoterdamoge ond more cosuolties during on eorthquoke> Dislonce of the a.eo from rhe epicenre.: Ateos neor epicenter v./rll be subJcted

to gredier sersrnic shokrng ond hencsustorn greoier domqge.the datnoge

'{ Scole volues o.e quolitotive, derived from freld interviews ond observotrons ofdomoge.L An eorfhq{roke of one mogniiude con produce eflects of different intensrties indiffeaenl oreos{ Useful os plotting Mercolli intensity values on o mop gives on informotrve potlernol lhe destrucrive effects os one moves away from the epicenter.

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People hdve d;ffi.ulry iiond'n9 DriveB feel rher. .ors Jhaling Some furn,t!.e brdks Looseb.icks fdil fron blildrngr Ddtuge ar ilighr to n\oderdte in well.bulr buildirgij co.side.obie'n

Dflverj hove r.oqble steering houses thdt d.e not bolred down hjghr sh;fr on rhei. foundoironJ.Ioll srructu.et tlch di foererr ond hihneyr fr'glrt tw si did tull Wcll-blilt buildings tuffe.5l'9ht dohdge Poo.ly 6urlr .r.u.t!re5 5uffer ieve.e ddhdge lree bron.hes b.@k Hill5'desmight ..d.k if the ground i5 wet Wdte. level. ri wlb highr chongeruffe. co.ride.dble ddndge llo!ser th.t o.e nor bolred down frove!nde.ground prper d.e b.okcf Ih g.olnd .rd.ks Rerervo,.r suffer

donrogeMosr burldr^gJand thei. folnddtionsa.e desiroyed. sore b.idges d/e dest.oyed Dnhi o.eserously ddruged. Ldrge ldrdslides o.cur. Woter ii th.own oi the bdnks of cohdl., /rve.s, ldker.

ihe g.oqid crockJ rn ltrge d.edr. Rlil.odd r.ockr o.e beht sliqhtiyMosi build,n95 colldpse 5oe b.idges o. deJt.oyed. L.rge c.ocks oppear ii rhe groqidUnderg.ound p'pelihs a.e dert..yed Roilroad t.ocki o.e bodly bent

People do not f@lony d.rh ndvenenie few people night noii.e hovernent if they @e dr .est o.d/or on th uppr fle.s of tollbuildiigs.

Mdny people indoo.s f@l novehen t Ho.9in9 oblects swr.9 bo.k and fo h Pcople ourdoo.s mrgh tnor.eoJize thqi oned.thqdke ir o..u..ingMosi people indoo.s feel ru@rent. l-ionging objects swiry. Disher, wiiddws,6nd doors.orile.Ihe o.thqudke feels likedhedry trlckhifii.g the w.lB A felv people drdoo.s hdy feeldpvelrent. Pd.ked .d.3 .o.k

Alnosreveryone feels hovehent. Sleping people6.e oulokend Doo.s swing ope. or ciose.Dishs d.e b.oken. Pr.tu.es on the wdll nove. shdll obJe. fs move ora.e tu.ned over. T.ee3 nrghtshdke. Liluidr 6ight spil{olt of opzn co.toihers

Eve.yon. feels n vement. People hdve irorbtewatking objecrs fotl froh shtves. pi.rures fsoff wollr Furniru.e rcve3. Plasre. in sqllr highr..dck. T.ee3 did bushes shdke Dahdge ir siighrin pdd.ly built buildingr No stru.tlrdl


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Comporing rtrlercolli ond Richter Scole: /(dgnitude Vs Intensity+ Becouse the qssessment systems developed by Mercolli ond Richter ore bosed onvery difterent c.iterio, it hos never 6een eosy to devise o fruly relioblecompqrison between them.+ Fig 72 6elow represents one qttempt io ochieve such o comporison; it olsoindicales how frequently Cqlifornio hos experienced eorlhgrjokes oi eoch level ofinlensity.

Eirtnqua&e vent scat dsc.iptoi,

Nlmb.r.r.iihqlrke.!e.1j m tu.hrci

dr. i3...h ortr:,.11.{.9 50 ye.r

1,,

lnrbufrent't ddecled o.t/ bf seino3raphrF.e6le ie[ oniy by sennnve rcopl.Slight ik. th. vb'arioisdlt ro a ps,na qht rorrModeat.: tl[e the pajns oir heiqroad vetr.L:.o.k it rr oore otjrcd!,..i!dng !i..d ie.a.rR.the. strong: Lll bt trjoa Deoi'.:.hr.h beri!.,.rSt.ongi noi peopl. trghtrn.o w,fno6bnrkei .l;ier ir1 .ur oi.lobotrrdjVert st.6na: ?en.rJ rifl,, "ar,:n.( rijr., i! jOestru.t,ve: ry dnvi, i i..lli]l.nr'...ldd .h nr:),j nlRqinols: -t.ji. , par( g.alir .-r.rj rrp.jjDisa5trour: e.olnd lra.ks btrdr man/ orrdnllJerlro/.c. undj,d.: o. ar.t no.?)v.y dis:'r.oqs: fo:! b! d,.?i jN.t Dr d3:jd.rrorcd art;..!:.:5 (rdrlw4,r ppej tr.d.aDl) our oiai'on 3rel hndrrd.r a.Jr:ooo:: CamJ brd r da.ri-rdCaett.ophi.: roiat dedrLo,o.: obre6 lhro@,nr.r!- 3ro!..1 fl5ei and taltr n.,a.a, f,a.ks open

Figurc 72 A comporison of the ,{ercolli dnd Richter Scotes

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d) Effects of ecrthquskes: HozardsThere ore severol hozords ossocioted wilh eorlhquokes:1) 6round shakinq and Ltquefaction2) Surface Foulting3) Tsunomi5) fires1) Ground Shoking cnd Liguefoction

,t Couses more domoge and results in nore loss of lives and ihjuraes thqn onyothe. eorthquoke hozqrd+ Strucllres built on poorly consolidaied or woter,soturoted moteriol oresubjecled to ground shoking of longer durotion o d gteoter omplitude thonthose built on solid bedrock+ Fill ond wote. saturoled sediments tend to liquefy, or behave like o fluid, in op.ocess known os liguefoction, jn which the strenglh ond sfiffness of o soil isreduced by eorfhquoke shoking+ When shoken, the indivduol grains lose cohesion ond fhe ground flows"> In 1964, hquefoction resulted in great danage in Niigata, Japan, where lorgedpartnent buildtngs were tipped on their sides ofter the water saturoted soil of thehr//tde collapsed> In 1964. t any hones were destroyed in Turnagoin Heights. A/aska when the clay losta// tts sttength during on eorthguake

Fig!.e 73. eesulr of lrllefdctio.duridg rhe Naigotq orthquok,Source: Notionol 6ophysicql

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2) Surfoce FoultingSurfoce foultlng is displocemeni thot reoches the eorfh's surfoce dur,ng slipolong c foultCommonly occurs wiih shollow eorthqookes, those with an epicnter les5 ihan2O km. Surfoce foulting olso iray occompony o sersmrc creep or ncturdl ormon-induced subsidence

Figure 74: Hector .,\ine surfoce .upture ofte. 1999 eo.rhquoke an southern cotifornid.sourcc: h f rp://eqf l!!!rt!91ls_91!sll) Isunomi

Destructive seo lvoves tllot are generoled by underwofer eorthquokes,volconic enuptions, or submorine lqndslidesff is coused by displocement of woler due to sudden ldrge scole chonges rnlhe level of the seo floor, e.g seobed collopses ocross o fou li coosing the seolevel to drop, rnoking o'hollow in the surfoce. Sec rushes bock in to fill thehollow. ihen spreods out in oll direciions as wqvesThis wove con trovel lhousqnds of miles ocross the oceon 01 speeds of severolhundred kilornelers per hour-In the open oceqn, isunomi woves ore less thon O.5m high.As o tsunarni enters shollow coostol woters. its speed dc.eose5 but rts hejghtcon rise qp to 65mA tsunomi corries o lot of energy when they hit the coosfft con colse mossive erosion of the coqstline os well as greot devostotion tocoostol properties

L

I

t+

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Exanple: July 1993 o 32nt high rsumni hit the south west coost of Hokkaido fol/owing anarby nvgnitude l8 earthguake under fhe sea h was beheved to hoye beencaused by slippage of the Eurotian Tectonic P/ote under the North Anerican PlateThe tsunahi ,1/os fravellinq ot an estinated 5)Okn/h when it tut the island ofOkushiri, caBing exfensive damage to fhe island ond caused the death of 15826 Decenber 2004 - a nagnitude 9 3 earfhguake ripped apart the seafloor off thecoast of northwesl Sunalra and generated tsunamts thot cause great devastationlo the coasla/ counlries around the Indian Ocean. The eafthguoke that generatedthe Lndion Ocean Eunani was lhe resu/t of the subduction the Indlan pldtebeneath the Sunda plate and the Surna hicroplote (a snaller, fragnentary'plote)(fis. 77)

Figwe 75. Plate main tsuhomi heodd west,edst lo N suhotro ondhovemeni bhihd the Asion tsunomi. Theond the ,rloldives. while rhe other heoddThoilond-Solrce:6eofiie OnLne

nrac 1- wndcn'. "rhc n!:i1!, xm' Dbrn(, C?rlrry Tlrtv

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Case Sfudy: The Indian Oceah fsunatniHow did lhe earlhquake happen and how dr'd it lead to the fsunani2The Indion plote subducts unde. the slndo and Bu.mo nicroplate of o rote of 6cmlyear. Subduclion is lnorked by the sundo rrench (Fig 76o)

Figure 76(a) Prior to fhe eqrfhquoke, showing subduction of the lhdion ptoteTh frictaon beiween the subducfing and overridrng plotes cdused fhe overlyrngEurmd plote to Jom ogoinsf fhe coniinued movement of the subdrctang plore.As o result, the overlyrng plore wos drsforted by iiress due to confrnurng burld up ofpress!r [Fiq 76 (b)]

Conrnenra 5hell' = zoonite;t -'.-iI+ lndirn plrre \i

|//'-- /*.':u'--.----.- ...-,'/\lnor"rod'pLonrau--'\ / -yodd,irolof.\rm'. lo Ge dro s!-/os:.


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up d woter column into o single lorge $/dve which. when it sank bdck, produced c flppleeffcl in lvh,ch o series of woves traveled out tFig 76(c))

Fig!.e 76(c) Th fr"iction sfickihg fhe plofes togethe. is ovefcorne by stress. The fort ofthe plote springs out ond up, roising the seo bed but lowering codstdl oreosrl A summary of the events leoding up to th 2004 fsunomi is represented inF,g 76dt' l" til",-;l|,r--.'-f-,l'-\,,.'"1 1""I , * I '*1 " ) /t ' '"'

i I l'rl.lI'''";.'.,", I ""'"l*lFig 76d : Generction of rhe 2004 tsunolni ( sihplified version)source: Geofile online

4) Londtlid".Eart hquake-l r igger ed londslidesregionsUnsloble regions of hillsides onddue fo ground movement

ore porticulorly dongerous in mounfoinoustnountcins in oddition to buildings may foll

. ........1i'-1 0'"0'"subsrdence

faull movemonl uo a.d alonq ralitr dov9m6nr u0 a.o- \ faul pra.e (meqalhrlsr)l. sluck ara ruplures

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When these moieriols gother speed os they nove, il con conlrabute tofurther deslraction of prope.ty ond loss of lives'L They con couse problems when they con close highwoys cnd roilroods needed(o" emergoncy ond r?5Lue operotrons.Exanrp/es:> 1920 - eatthguake n Gansu, most of the lA0,OAo deaths resutted when c/iffsconposed of /oess collopsed> 1959 earthquake in /'4adison Canyon, tlontdnd, generated o na.yor rock sltde> 1970 earthquake n peru dislodged a huqe block of tce froh the a/acEr of MtIluoscaran It caused on avalonche thot destrored ZOO OOO honi n the townof yungay. 7o.O0O people were ki//ed and 5O,0OO nlured.

Fisve 77. Effecrs of eorrhquokes on hillstope re5idenriol dreos50!.ce: Notronot Geophy5rcot Dota Cenie.5) Fires

! Molor hozord in urbon oreos offected by eqrthquokes'{ Result from broken o( severed electtical ond gos lines.{ Fires ihot begin os o resalt of eorfhquoke ocfivity ore often unconfroiloblecnd ccn couse the most domoge.{ Flommoble moterio's or debris .eleosed fron the eo.thquoke feed the flomesof the fire, thus cousing it to spreod out of control.+ Woter moins are broken os o resulf of the powrful edrthguoke vibrations,therefore, no wcter is ovoilcble for firefighters io puf oul the flomes dndrescae lhe people{- Ccu5e donoge to property ond infrostructure.Exatnples:> During the septenber l. 1923, earthguake in Japan, fire, destrcyed ItZ of fhe housesin ,okyo and d// the houses tn yokohomo tn totol, 576,262 houses were destroled bt,fires and 113.OOO dled'L Duriag the 1989 Lat a Prieto earthqudke, a t're brake out n the Marina dtrtri.t ofsan Franc,sco but wos cantained withn d snoltarea|0


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*pefet to nanagenent of volconic hazards (section 3c) for details on sinilar concepfs{ Sinilor to volconic erupfions, eo.thquokes con be monoged in the following

) P.ed,ction) Mitigotion) Response+ Jusi like in the monogement of volconic eruplions, such meosures hove beenimplemented with some degree of success in nony countries oround lhe world.+ In this section, we examine the vorious neosures in place lo monogeeorthquoke hozords. Similor to the mondgement of volcqnic hozords, o combinotionof meosures ore token to monoge eorthquoke hozords_ Poy ottenfion to theetfectiveness and limitoiions of eqch mqsure.

i sr,".r t.". i1)2',)3)4)5)

1)2)3)4)

Monogemenl of Forlhquoke Hozords

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ei) Predicting Eorthguokes'l- The gool of eorthguoke prediction as to give wo.ning of potentiolly domogingearihguokes eorly enough to ollow appropriofe response io the disqster, enoblingpeople to mininize loss of life ond properly{ Meoningful eorthquoke prediction should (ideollyl) include fhe following :) Locdtion: Whre is fhe eorthquake likely occur2) Time : When is the eorthguok lkely to occur?) Magnitud: How destruclive lvill the ea.fhquoke be2'I There ore t!r,/o woys thot eorthquoke prediction con be conducted: short termond long-lerm predictiono Short-1rm p.ediction: slch predrctron involves monitoring srgns ofearthguake precursors whrch would suggest the occurrenc of o potenlioledrthquoke

o Long term predicfionr Such predrcrion jnvolves predicfing the nexteorlhquake based on the previo!s pottern of sersmrc octivrty jn o porticulorlocotion An exomple is recurrnce interval predrctron{ A cornbinotion of these nelhods ore used in eorihquoke predicfion progrommes:

. Only 4 notrons the United Siotes, Jdpon. Russro ond Chino hove governhenisponJo.d eorthq!oke pl"edrction pro.romns. Include ldbororory ond tretd sirdies of the behovjorr of rocks before, duflng. dnddfter moJor eorihquokes. os well os l1lonriorrng oct,vity olong rnoJor ocfrve foults.. In th U5. mosi eorthquoke predictron work rs conducted by fhe Unrled SratesGeoloq.ot survey (U sGs).

ll2

Short-trm prediction.t Most eorlhquokes are preceded byshoat termond long te.m chonqes withinthe Eorth Such chonges ore known os precursors..l Even ihough such precursors con only suggest the probabilityof on eorthquokeoccurring ( ie: thy connot os5ure thoi on eorfhquoke will definilely occur) ,they still remain extrernely useful in predicting lhe occurrence at eorthquokes.1. Seismic monitoring

1 Most moJor eoathqLtokes ore preceded by occurrence of smoller mognitudeeorthquokes ( also known os "foreshocks").l- By monitoring such seismic octivity, scientists cqn predicl when the nexi moior


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+ Tiltmelers con be used to meosure extremely ihese slight chonges in the ongleof the ground surfoce. ( Refer io section 3c).1- Aport fron liltmelers, scienfists hove 6een exploring new woys of meosurrngground deformolion..L One such new iechnology is 6lobcl Eorthguoke Sotellite System, or 6ESS.'l Put simply, it ollor../s scientisfs io detect.ninute deformdtions in ihe Eorth'scrust. (Notionol Geogrophic News, July 20. 2004)1 However, the uiility of such o technology in p.ed,ctang eorthquokes remoins 10Eg. Hai cheng earthquake, China (1974): Apart fron re/yng on foreshocks. scientists a/sonotrced changes in ldnd elevation prior to the edrfhguakeEg: Long Valley, Coliforhia: Tiltmefers are used extensively in earthguake prone Coliorniato check for sgns of ground defornation.

3-rrqfic Animol Behovioua

I ft is cloimed thoi onirnols cqn detecf the P wave genetated by the rupture ofcn eorihg{toke, even it Ihe woves ore 1oo smdll for humons senses.+ These woves lrovel foster than the S wove ond Royleigh eorfhquoke woves'ihdi most slrongly shoke the gl.ound ond couses the mosf domcge; when thishdppen5, onimrrl5 con delect the incoming eorihquoke wqve, ond stort behovingoqilotedly or nervously.{ Others cloitn however,ihdt th cor.elotion between onimol beohviour ondeorthquoke occurrence is d!bious This is becouse onimol behoviour rs

influenced by o nryriod of foctors other ihon potentiol eqrthquokes ( Eg:climotic chdnges) 5cientific resecrch in fhis oreo is ongoing.+ Er.otic onimol behovior hos been used os worning signqls of eorthquakes inChino os some onimols feel sound vibrotions ond ground vibrqtions too slighlfor humans fo nolice

Eg: Sctenttsts successfu//y predtcted the J975 HaEheng earthguaAe bdsed the observatjanof unusuo/ aninnl beha our foreshocks and tiltii.j of the qround elevatrcnI However, the qnpredictobility of onimol behoviour hos led mony to disregordit in eorfhquoke prediction- This hod led to disosfaous consdquences in some coses_

Eg: On A4oy 5th, nany Chnese /oca/s noticed thousands of frogs on the tnoveA4an)/ Chtnese sensed the nigration as a bdd onen of a conin., noturol dEaster, but theI lit


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Chuese governnent to/d then fhol il was Just a natural nigratlon for the purpose ofOn,tL\ondoy. 12th af May, at about 2:45pn, centual China regon recor.Jed o 7 |-nognitudeguake which occured near Wenchuan County. 9chl6n province, thot killed near/y 10,0OO

4- Other Precursors't Fluctqcfiohs ih the woter level of wells: Ground deformotion brought oboutby stresses exefied belote cnd impending eorthquoke con contribute to

chonges in woter toble levels.Eg: Hoicheng earthguake, China (1975): Fluctuations in water table was reported pflor to the

{ Locol chonges in the Eorth's mognefic field ond the elecfric resisfdnce ofthe ground: It is believed fhot the friction bLrilt up in faulfs releoseselectricity-Eg, Lonw Prieto earthquake(|9g9) rwe/ve doys before the Lona Prieta eorthqudke. lorgeelectromagnetic wove signals were detected by the No,y

Long term p{gdiction: Recurrence fntervol Prediction+ Recurrence inieTvol is the fime between eorthquokes of similor magnitude! Long-ierrn paediction is based moinly on lhe knowledge o{ when ond whereeorlhquokes hove occuared in the pc5t Thus, knowledge of presenf tecionrcselting. histo.icol records, and geologicql records ore studied lo determinelocofions and recumence intervols of eorthquokes..L Compored to short term prediction methods. long term p.ediction cannoideletmine when exoctly qn eorthquoke moy occur It simply provides o generoliime frdme wilhin which on eorthqltoke of o porticulor mognaiude moy occur.

Scientisis con determine the tecur(ence intervol of eorfhquakes forindividudl foulis by determining the oges of layers ol rocks ond/or sedimentAnolysis of how much time hos elopsed since lhe losf eorihquqke dnd theomoqnt of energy thot wos releosed (mognitude) help reveol which foulls moybe slor,ng up sufficaenl slroin for eqrthq(qkes in the.elotively neor future.

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{ The longer the period of dolo ovqiloble, the better the prediction.

FiqJre 78. 'fhe expected recur(ence intervsl for o greof eorrhquoke in the New Modridseishic zone con be stimoted from 6pS obsecvotions showihg ot most o fes, hm/y. offoult-pcrollel motion, ossuming the horizontat slip in ihe greof 1Bl1_l8lZ eorthguokeswos o few meters, os inferred f.oh historicol dccounfs_5ou.ce: http://focility.unovco.orqlproject suppori/scienceljnt.dplote.htlL!

Hew l,ladrid Ec(hquake Recu.rEnce tnr.vEt

6

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t13?s/G:SS:-^;;r5

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withstond both horizontol ond ve.ticol shokingSjze qnd shqper The size ond shope of o bualding con olso offect its resislonceto eqrthqqokes. Rectangular box-shaped buildings ore inherenlly stronger thonthose of irregulqr size or shope \ecouse diff erent ports of on irregulorbuilding moy swoy ot different .otes, increosing stress ond likelihood ofstructul.ol foilure.structure: Toll buildings, such os skysc.opers, must be designed so thot acerloin omouni of swoying con occur, but not so much thot they touchneighbouring buildings during swoying Severol woys in which the structure conbe oltered lo oc(ommodote v'brolrons.

Fromei of bu'ldin95 con be modrfied 10 withstond sidewoys forces or resisl forcesby bendrng Steel, for exomple, obsorbs o lot of e ergy when at is deformedDdmpers con be uslolled in th str{tclurdl frsme of c buildrng to obsorb some ofthe eneryy gotng into the building from the shoking ground during sn eorthgudk.As ih building begins io shoke, the ddnrpers would move bdck ond forth tocompen.ole for ihe vrbrotion of th shock

Fosndataon anchoring keeps d struciure dnd ris bose moving os d unrt v./hen the9rolnd begtns fo q!dkeEose isolotion dllows o structures foundotron and the ground to rnove asninrmrz n9 ihe fo.cs on the building rtslf

; Pile foundotions reoch down through unsfoble soil to ihe bedrock benearhdddd stob,l,ty

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I rl l rlll

!

Figure 79: Eorthquoke resistont sfructures

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2. Hazard l4appinqEorlhguoke hozord rnops oTe consiructed bosed on the qeology ond sifechorocterislics of on oreo

+ As some oreos oTe more ot risk to orthquoke domoge ihon others, those thoto.e more susceptible to eorthquoke hozords cqn be eosily identified fromhqzord mqps_4e As effects of eorlhquokes con be felt for owoy from the origin, hozord mopscon be used by londuse plonners fo plon profective zoning ond reslricldeveloprnent in high-risk d.eos to ninimize the possible impocts.Eg: In Californto, there is a ban on new buildin(ts @ithin 40n of a known fau/t /ne.L Used by evocuotion plonners to plon evocuotion ond emerg ency relief toutes.l When combined with legisldtion, eorth quoke zoning renoins the most powerfulmethod of mitigqting eorlhquoke inpocl

Liquefaction Potentiat lndex >.15Probability of Exceedance 27o in 50 years:, i

J@-,.",,it:: :'"" l

Figu'"e 80:Liquefaction Risk /vlapDu.ing an Edrthquoke

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() lvlagnitud S-5 and g.eatef

{ vocuqfaon drills con olso be conducted to increose community preporedness.

Figure 81. Eorthquoke Hozord A,lop of fhe Unifed Stotes3. Evacuafion neasufes

! Once indicotions from prediction nrethods dI.e recerved thoi dn eorlhquoke iscboui to result, evdcuolion of people con be corried out to minimize lois ofHowevet, the lime frome will be short os fotecasls are bosed on weeks or evendoys ond on evocr-roiion plon musl be olreody put anto pion in order to coray itout successfully.

+ Dotq olso hos to be rel,oble ,n order to worront evqcqotion os seisnic tremorsmoy olso be prodr..lced by other lectonic notions.

4. Comnunity Preparcdness Programnest Public educotion is olso necessory fo increose community preporedness forevocuotion ond increose communily qworeness qbouf potentiol eorthqooke

hozords.

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Eg. Earthquake drills are conducted regularly in Japanese schools. fB capita/ ctry. rokyo,ho/d annual dn//s on 1 Septenber (tradttiona/ly referred to as ,Disoster Ddy,. in nenory ofthe 6reat Kdnlo Eaffhguake which struck ToAyo in 1923)Con lro I e d Ea rthgua k e s+ Controlled fluid inlection is o poieniiol scientific tool for ttiggering foullingond redoctng stroin buildup on fault segments.* Periodic wqie. injectaon mighi trigger smoll eorfhguokes to felieve strqrn on ofault, perhops preventing or reducing th e intensity of o lorger seismic evenf{ However, opplying thts method to some oreos such os 'locked.sections of theson Andreos fcult could be dongerous os the high sfress levels could teigger olorge mognif ude eorthquok.{ Controlled teleose of eorthquoke enetgy also results in problems. For exomple,in on oreo where o mognitude 8.0 eorihquoke is expected every 100 yeors. omagnitude 5O event hds to be triggered olmosi everydoy for lO0 yeors to

releose the sqme omoLlnt of energy_eiii) Responses

1, Emetgency relief ,s impo.tant when locol comnunitie5 hove been vocuoted orrescued from oreos otfected 6y earfhquokesEmergency personnel nust be ovciloble ond well,prepo.ed to rescue peoplefropped in the rubble ond to provide emetgency telielEmergency .lief comprises the provision of shelter, food, bosic hygreneomenrttes ond medicol core{ In iess developed counfries, inte.nolionol oid js ofin required os locolTeso!rces mcy be overwhelmed

Eg, 'Uoy 6 Javo earthquake. /L4easuring 6 t on the Ritcher Scale, the earthquake struckYogfakorla and caused massive destruction lhe oppeal to donor governnenfs and agenciescane after offjcn/s from the UN ( Unit'ed Nations) ond the ped Cross net rt ,eneva toofganize the nternationo/ response to the quake. At least 12 countfies pledged oid n the fornof noney, doctors and nurses. food and pravisions Sngapore senf fescu; tuans (stngaporeCivil Defence Force dnd Singapore Amed Forces) to help in search-and rescue efforts.

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i) Describe the chorocferistics of eqrfhcuqkes.l4usl Include: (Section 4q)) Eo.thquoke Focus ond epicenlre) Seisrnic Wqves ( P ond S woves, L qnd Royleiqh woves)ii) Distinouish beiween moqnitude ond intensitv of eorthouqkes,When distrnguishing between mognilude ond inlensity, necessory 10 htghlighl oreas of

i) /Ueasurenent of earthquake strengthj Bofh tneosur the strengrh ofeorlhquokPs,n d, f lc"enl woytr) scales: fhey ore represenled 6y different scoles of meqsurementL--------- -----------Ilrlust Include: (Seciion 4c)) Mognifqde ond Intensity) Qichter Scole ond Mercolli 5cole

iii) Discuss the effecfs of earthquckes./Uusf Include: (Section 4d)> lazarcl) Ground Shoking ond Liquefcction, Surfoce Fouliihg, Tsunomi, Londslide, F,resiv) With reference to cqse sfiidies, ossess ottempts to mdnoqeeorthquqke hczqrds-

Note:When ossessrng moncgement slrotegres. ii is necessory to::> Addtess exomples where lhe sfrslegies hsve proven fo be successful ( or NoIunsrccessful) rn monagrng fhe impocts of eorthquokes.) I1 is olso necessary to explo'n why these sltolzgies ho\/e 6een successful ( orI'lust Include: (Section 4e ond 4f)) Prediction, mitigotion ond response) Evoluotion of prediclion, mitigdtion qnd response sl"ategies

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Earthquake Hazards Responses