,illu/ration3 ,_m build+s 9 ,*>le/on1 ,s\? ,c>ol9a1 7 damag$ or de/roy$ by ! l>ge e>?quake t occurr$ ,augu/ #ca1 #ahhf4 ,u4,s4 ,dep>tm5t ( ! ,int]ior _/ ,u4,s4 ,geological ,survey ,e>?quakes by ,kaye ,m4 ,%$lock & ,l\is ,c4 ,pakis] ,= sale by ! ,u4,s4 ,gov]nm5t ,pr9t+ ,(fice ,sup]9t5d5t ( ,docum5ts ,mail ,/op3 ,,ssop1 ,wa%+ton1 ,,dc #bjdjb-icbh ,"o ( ! mo/ fright5+ & de/ructive ph5om5a ( nature is a sev]e e>?quake & its t]rible aft]effects4 ,an e>?quake is a sudd5 movem5t ( ! ,e>?1 caus$ by ! abrupt release ( /ra9 t has accumulat$ ov] a long "t4 ,= hundr$s ( millions ( ye>s1 ! =ces ( plate tectonics h %ap$ ! ,e>? z ! huge plates t =m ! ,e>?'s surface sl[ly move ov]1 "u1 & pa/ ea* o!r4 ,sometimes ! movem5t is gradual4 ,at o!r times1 ! plates are lock$ toge!r1 unable to release ! accumulat+ en]gy4 ,:5 ! accumulat$ en]gy gr[s /rong en\gh1 ! plates break free4 ,if ! e>?quake occurs 9 a populat$ area1 x may cause _m dea?s & injuries & ext5sive prop]ty damage4 ,today we are *all5g+ ! assumption t e>?quakes mu/ pres5t an uncontrollable & unpr$ictable haz>d to life & prop]ty4 ,sci5ti/s h begun to e/imate ! locations & likelihoods ( future damag+ e>?quakes4 ,sites ( greate/ haz>d are be+ id5tifi$1 & def9ite progress is be+ made 9 design+ /ructures t w )/& ! effects ( e>?quakes4 ,illu/ration3 ,,usgs sci5ti/ uses portable seismic record+ equipm5t ne> ,m\nt ,/4 ,hel5s1 ,wa%+ton4 ,e>?quakes 9 ,hi/ory ,! sci5tific /udy ( e>?quakes is comp>atively new4 ,until ! #ah? c5tury1 few factual descriptions ( e>?quakes 7 record$1 & ! natural cause ( e>?quakes 0 little und]/ood4 ,^? :o did look = natural causes (t5 rea*$ conclusions t seem fanciful today2 "o popul> !ory 0 t e>?quakes 7 caus$ by air ru%+ out ( cav]ns deep 9 ! ,e>?'s int]ior4 ,! e>lie/ e>?quake = :i* we h descriptive in=mation occurr$ 9 ,*9a 9 #aagg ,b4,c4 ,! ,*9ese e>?quake catalog describes sev]al doz5 l>ge e>?quakes 9 ,*9a dur+ ! next few ?\s& ye>s4 ,e>?quakes 9 ,europe are m5tion$ z e>ly z #ehj ,b4,c41 b ! e>lie/ = :i* we h "s descriptive in=mation occurr$ 9 ! mid-#af? c5tury4 ,! e>lie/ kn[n e>?quakes 9 ! ,am]icas 7 9 ,mexico 9 ! late #ad? c5tury & 9 ,p]u 9 #adga1 b descriptions ( ! effects 7 n well docum5t$4 ,by ! #ag? c5tury1 descriptions ( ! effects ( e>?quakes 7 be+ publi%$ ar\nd ! _w--al?\gh ^! acc\nts 7 (t5 exagg]at$ or di/ort$4 ,! mo/ widely felt e>?quakes 9 ! record$ hi/ory ( ,nor? ,am]ica 7 a s]ies t occurr$ 9 #ahaa-ab ne> ,new ,madrid1 ,mo4 ,a great e>?quake1 ^: magnitude is e/imat$ to be ab\t #h1 occurr$ on ! morn+ ( ,decemb] #af1 #ahaa4 ,ano!r great e>?quake occurr$ on ,janu>y #bc1 #ahab1 & a ?ird1 ! /ronge/ yet1 on ,febru>y #g1 #ahab4 ,aft]%ocks 7 ne>ly cont9u\s betwe5 ^! great e>?quakes & cont9u$ = mon?s aft]w>ds4 ,^! e>?quakes 7 felt by p z f> away z ,bo/on & ,d5v]4 ,because ! mo/ int5se effects 7 9 a sp>sely populat$ region1 ! de/ruction ( human life & prop]ty 0 slight4 ,if j "o ( ^! enorm\s e>?quakes occurr$ 9 ! same area today1 millions ( p & build+s & o!r /ructures wor? billions ( doll>s w\ld be affect$4 ,illu/ration3 ,! great #aijf ,san ,francisco e>?quake & fire de/roy$ mo/ ( ! city & left #bej1jjj p homeless4 ,! ,san ,francisco e>?quake ( #aijf 0 "o ( ! mo/ de/ructive 9 ! record$ hi/ory ( ,nor? ,am]ica--! e>?quake & ! fire t foll[$ kill$ ne>ly #gjj p & left ! city 9 ru9s4 ,! ,alaska e>?quake ( ,m>* #bg1 #aifd1 0 ( great] magnitude ?an ! ,san ,francisco e>?quake2 x releas$ p]haps twice z mu* en]gy & 0 felt ov] an area ( almo/ #ejj1jjj squ>e miles4 ,! gr\nd motion ne> ! epic5t] 0 s viol5t t ! tops ( "s trees 7 snapp$ (f4 ,"o hundr$ & f\rte5 p 7"s z f> away z ,cali=nia7 di$ z a result ( ?is e>?quake1 b loss ( life & prop]ty w\ld h be5 f> great] _h ,alaska be5 m d5sely populat$4 ,:]e ,e>?quakes ,occur ,! ,e>? is =m$ ( sev]al lay]s t h v diff]5t physical & *emical prop]ties4 ,! out] lay]1 :i* av]ages ab\t #gj kilomet]s 9 ?ickness1 consi/s ( ab\t a doz5 l>ge1 irregul>ly %ap$ plates t slide ov]1 "u1 & pa/ ea* o!r on top ( ! p>tly molt5 inn] lay]4 ,mo/ e>?quakes occur at ! b\nd>ies :]e ! plates meet4 ,9 fact1 ! locations ( e>?quakes & ! k9ds ( ruptures !y produce help sci5ti/s def9e ! plate b\nd>ies4 ,illu/ration3 ,diagram ( plate b\nd>ies & e>?quake locations4 ,!re are ?ree types ( plate b\nd>ies3 spread+ zones1 trans=m faults1 & subduction zones4 ,at spread+ zones1 molt5 rock rises1 pu%+ two plates ap>t & add+ new mat]ial at _! edges4 ,mo/ spread+ zones are f\nd 9 oceans2 = example1 ! ,nor? ,am]ican & ,eurasian plates are spread+ ap>t along ! mid-,atlantic ridge4 ,spread+ zones usually h e>?quakes at %all[ dep?s 7)9 #cj kilomet]s ( ! surface74 ,trans=m faults are f\nd :]e plates slide pa/ "o ano!r4 ,an example ( a trans=m-fault plate b\nd>y is ! ,san ,&reas fault1 along ! coa/ ( ,cali=nia & nor?we/]n ,mexico4 ,e>?quakes at trans=m faults t5d to occur at %all[ dep?s & =m fairly /raight l9e> patt]ns4 ,illu/ration3 ,map explanation3 yell[ l9es1 plate ,b\nd>y4 ,subduction zones are f\nd :]e "o plate ov]rides1 or subducts1 ano!r1 pu%+ x d[nw>d into ! mantle :]e x melts4 ,an example ( a subduction-zone plate b\nd>y is f\nd along ! nor?we/ coa/ ( ! ,unit$ ,/ates1 we/]n ,canada1 & s\!rn ,alaska & ! ,aleutian ,isl&s4 ,subduction zones are *>act]iz$ by deep-ocean tr5*es1 %all[ to deep e>?quakes1 & m\nta9 ranges conta9+ active volcanoes4 ,e>?quakes c also occur )9 plates1 al?\gh plate-b\nd>y e>?quakes are mu* m common4 ,less ?an #aj p]c5t ( all e>?quakes occur )9 plate int]iors4 ,z plates cont9ue to move & plate b\nd>ies *ange ov] geologic "t1 weak5$ b\nd>y regions become "p ( ! int]iors ( ! plates4 ,^! zones ( weakness )9 ! cont95ts c cause e>?quakes 9 response to /resses t orig9ate at ! edges ( ! plate or 9 ! deep] cru/4 ,! ,new ,madrid e>?quakes ( #ahaa-ab & ! #ahhf ,*>le/on e>?quake occurr$ )9 ! ,nor? ,am]ican plate4 ,illu/ration3 ,damag$ h\se4 ,h[ ,e>?quakes ,happ5 ,an e>?quake is ! vibration1 sometimes viol5t1 ( ! ,e>?'s surface t foll[s a release ( en]gy 9 ! ,e>?'s cru/4 ,?is en]gy c be g5]at$ by a sudd5 dislocation ( segm5ts ( ! cru/1 by a volcanic eruption1 or ev5 by manmade explosions4 ,mo/ de/ructive quakes1 h[ev]1 are caus$ by dislocations ( ! cru/4 ,! cru/ may fir/ b5d & !n1 :5 ! /ress exce$s ! /r5g? ( ! rocks1 break & 8snap0 to a new position4 ,9 ! process ( break+1 vibrations call$ 8seismic waves0 are g5]at$4 ,^! waves travel outw>d f ! s\rce ( ! e>?quake along ! surface & ?r\gh ! ,e>? at v>y+ spe$s dep5d+ on ! mat]ial ?r\gh :i* !y move4 ,"s ( ! vibrations are ( high en\gh frequ5cy to be audible1 :ile o!rs are ( v l[ frequ5cy4 ,^! vibrations cause ! entire planet to quiv] or r+ l a bell or a tun+ =k4 ,a fault is a fracture 9 ! ,e>?'s cru/ along :i* two blocks ( ! cru/ h slipp$ ) respect to ea* o!r4 ,faults are divid$ into ?ree ma9 gr\ps1 dep5d+ on h[ !y move4 ,normal faults occur 9 response to pull+ or t5sion2 ! ov]ly+ block moves d[n ! dip ( ! fault plane4 ,?ru/ 7rev]se7 faults occur 9 response to squeez+ or compression2 ! ov]ly+ block moves up ! dip ( ! fault plane4 ,/rike-slip 7lat]al7 faults occur 9 response to ei!r type ( /ress2 ! blocks move horizontally pa/ "o ano!r4 ,mo/ fault+ along spread+ zones is normal1 along subduction zones is ?ru/1 & along trans=m faults is /rike-slip4 ,illu/ration3 ,normal ,fault4 ,blocks are pull$ ap>t ,illu/ration3 ,?ru/ ,fault4 ,blocks are pu%$ toge!r ,illu/ration3 ,/rike-,slip ,fault4 ,blocks slide pa/ ea* o!r ,geologi/s h f\nd t e>?quakes t5d to reoccur along faults1 :i* reflect zones ( weakness 9 ! ,e>?'s cru/4 ,ev5 if a fault zone has rec5tly exp]i5c$ an e>?quake1 h[ev]1 !re is no gu>antee t all ! /ress has be5 reliev$4 ,ano!r e>?quake c\ld /ill occur4 ,9 ,new ,madrid1 a great e>?quake 0 foll[$ by a l>ge aft]%ock )9 #f h\rs on ,decemb] #af1 #ahaa4 ,fur!rmore1 reliev+ /ress along "o "p ( ! fault may increase /ress 9 ano!r "p2 ! ,new ,madrid e>?quakes 9 ,janu>y & ,febru>y #ahab may h result$ f ?is ph5om5on4 ,illu/ration3 ,diagram ( ,e>?'s lay]s & seismic wave propagation4 ,! focal dep? ( an e>?quake is ! dep? f ! ,e>?'s surface to ! region :]e an e>?quake's en]gy orig9ates 7! focus74 ,e>?quakes ) focal dep?s f ! surface to ab\t #gj kilomet]s 7#dc4e miles7 are classifi$ z %all[4 ,e>?quakes ) focal dep?s f #gj to #cjj kilomet]s 7#dc4e to #ahf miles7 are classifi$ z int]m$iate4 ,! focus ( deep e>?quakes may rea* dep?s ( m ?an #gjj kilomet]s 7#dce miles74 ,! focuses ( mo/ e>?quakes are conc5trat$ 9 ! cru/ & upp] mantle4 ,! dep? to ! c5t] ( ! ,e>?'s core is ab\t #f1cgj kilomet]s 7#c1ifj miles71 s ev5 ! deepe/ e>?quakes orig9ate 9 relatively %all[ p>ts ( ! ,e>?'s int]ior4 ,! epic5t] ( an e>?quake is ! po9t on ! ,e>?'s surface directly above ! focus4 ,! location ( an e>?quake is commonly describ$ by ! geographic position ( its epic5t] & by its focal dep?4 ,e>?quakes b5ea? ! ocean floor sometimes g5]ate imm5se sea waves or tsunamis 7,japan's dread 8huge wave074 ,^! waves travel across ! ocean at spe$s z great z #ifj kilomet]s p] h\r 7#eig miles p] h\r7 & may be #ae met]s 7#di feet7 high or high] by ! "t !y rea* ! %ore4 ,dur+ ! #aifd ,alaska e>?quake1 tsunamis engulf+ coa/al areas caus$ mo/ ( ! de/ruction at ,kodiak1 ,cordova1 & ,sew>d & caus$ sev]e damage along ! we/ coa/ ( ,nor? ,am]ica1 p>ticul>ly at ,cresc5t ,city1 ,calif4 ,"s waves rac$ across ! ocean to ! coa/s ( ,japan4 ,illu/ration3 ,tsunami de/ruction on ,kamehameha ,av5ue on ,hilo's wat]front1 #aidf4 7,photograph provid$ by ! ,u4,s4 ,army ,corps ( ,eng9e]s47 ,liquefaction1 :i* happ5s :5 loosely pack$1 wat]-logg$ s$im5ts lose _! /r5g? 9 response to /rong %ak+1 causes major damage dur+ e>?quakes4 ,dur+ ! #aihi ,loma ,prieta e>?quake1 liquefaction ( ! soils & debris us$ to fill 9 a lagoon caus$ major subsid5ce1 fractur+1 & horizontal slid+ ( ! gr\nd surface 9 ! ,m>9a di/rict 9 ,san ,francisco4 ,illu/ration3 ,liquefaction ( s&s & debris caus$ major damage ?r\gh\t ! ,m>9a di/rict 9 ,san ,francisco dur+ ! ,loma ,prieta e>?quake4 ,l&slides trigg]$ by e>?quakes (t5 cause m de/ruction ?an ! e>?quakes !mselves4 ,dur+ ! #aifd ,alaska quake1 %ock-induc$ l&slides deva/at$ ! ,turnaga9 ,heights resid5tial developm5t & _m d[nt[n areas 9 ,an*orage4 ,an obs]v] gave a vivid report ( ! breakup ( ! un/able e>? mat]ials 9 ! ,turnaga9 ,heights region3 ,i got out ( my c>1 ran nor?w>d t[>d my driveway1 & !n saw t ! bluff _h brok5 back approximately #cjj feet s\?w>d f its orig9al edge4 ,additional slump+ ( ! bluff caus$ me to return to my c> & back s\?w>d approximately #ahj feet to ! corn] ( ,mc,collie & ,turnaga9 ,p>kway4 ,! bluff sl[ly broke until ! corn] ( ,turnaga9 ,p>kway & ,mc,collie _h slump$ nor?w>d4 ,illu/ration3 ,_m homes 7 damag$ by l&slides trigg]$ by ! #aifd ,alaska e>?quake 7above7 & ! #aihi ,loma ,prieta %ock 7bel[74 ,illu/ration3 ,home damag$ by l&slide trigg]$ by ! #aihi ,loma ,prieta %ock4 ,illu/ration3 ,sci5ti/ exam9+ seismographic equipm5t4 ,measur+ ,e>?quakes ,! vibrations produc$ by e>?quakes are detect$1 record$1 & measur$ by in/rum5ts call$ seismographs4 ,! zig-zag l9e made by a seismograph1 call$ a 8seismogram10 reflects ! *ang+ int5sity ( ! vibrations by respond+ to ! motion ( ! gr\nd surface b5ea? ! in/rum5t4 ,f ! data express$ 9 seismograms1 sci5ti/s c det]m9e ! "t1 ! epic5t]1 ! focal dep?1 & ! type ( fault+ ( an e>?quake & c e/imate h[ mu* en]gy 0 releas$4 ,! two g5]al types ( vibrations produc$ by e>?quakes are surface waves1 :i* travel along ! ,e>?'s surface1 & body waves1 :i* travel ?r\gh ! ,e>?4 ,surface waves usually h ! /ronge/ vibrations & probably cause mo/ ( ! damage done by e>?quakes4 ,body waves are ( two types1 compressional & %e>4 ,bo? types pass ?r\gh ! ,e>?'s int]ior f ! focus ( an e>?quake to di/ant po9ts on ! surface1 b only compressional waves travel ?r\gh ! ,e>?'s molt5 core4 ,because compressional waves travel at great spe$s & ord9>ily rea* ! surface fir/1 !y are (t5 call$ 8prim>y waves0 or simply 8,p0 waves4 ,p waves pu% t9y p>ticles ( ,e>? mat]ial directly ahead ( !m or displace ! p>ticles directly beh9d _! l9e ( travel4 ,%e> waves d n travel z rapidly ?r\gh ! ,e>?'s cru/ & mantle z d compressional waves1 & because !y ord9>ily rea* ! surface lat] !y are call$ 8second>y0 or 8,s0 waves4 ,in/ead ( affect+ mat]ial directly beh9d or ahead ( _! l9e ( travel1 %e> waves displace mat]ial at "r angles to _! pa? & are !re=e sometimes call$ 8transv]se0 waves4 ,illu/ration3 ,diagram ( propagation ( seismic waves4 ,! fir/ indication ( an e>?quake is (t5 a %>p ?ud1 signal+ ! arrival ( compressional waves4 ,?is is foll[$ by ! %e> waves & !n ! 8gr\nd roll0 caus$ by ! surface waves4 ,a geologi/ :o 0 at ,valdez1 ,alaska1 dur+ ! #aifd e>?quake describ$ ?is sequ5ce3 ,! fir/ tremors 7 h>d en\gh to /op a mov+ p]son1 & %ock waves 7 imm$iately noticeable on ! surface ( ! gr\nd4 ,^! %ock waves cont9u$ ) a r long frequ5cy1 :i* gave ! obs]v] an impression ( a roll+ feel+ r ?an abrupt h>d jolts4 ,aft] ab\t #a m9ute ! amplitude or /r5g? ( ! %ock waves increas$ 9 int5sity & failures 9 build+s z well z ! froz5 gr\nd surface began to occur4444 ,aft] ab\t #c m9utes ! sev]e %ock waves end$ & p began to react z c\ld be expect$4 ,illu/ration3 ,l>ge e>?quakes cause m damage ea/ ( ! ,rocky ,m\nta9s2 ?is map %[s areas t suff]$ major ar*itectural damage 7/rip$ areas7 & m9or damage 7dott$ areas7 dur+ ! magnitude-#h e>?quakes 9 ,new ,madrid & ,san ,francisco & ! small] b /ill damag+ quakes 9 ,*>le/on & ,san ,f]n&o4 ,! sev]ity ( an e>?quake c be express$ 9 sev]al ways4 ,! magnitude ( an e>?quake1 usually express$ by ! ,ri*t] ,scale1 is a measure ( ! amplitude ( ! seismic waves4 ,! mom5t magnitude ( an e>?quake is a measure ( ! am\nt ( en]gy releas$--an am\nt t c be e/imat$ f seismograph record+s4 ,! int5sity1 z express$ by ! ,modifi$ ,m]calli ,scale1 is a subjective measure t describes h[ /rong a %ock 0 felt at a p>ticul> location4 ,! ,ri*t] ,scale1 nam$ aft] ,dr4 ,*>les ,f4 ,ri*t] ( ! ,cali=nia ,in/itute ( ,te*nology1 is ! be/ kn[n scale = measur+ ! magnitude ( e>?quakes4 ,! scale is log>i?mic s t a record+ ( #g1 = example1 indicates a di/urbance ) gr\nd motion #aj times z l>ge z a record+ ( #f4 ,a quake ( magnitude #b is ! smalle/ quake normally felt by p4 ,e>?quakes ) a ,ri*t] value ( #f or m are commonly consid]$ major2 great e>?quakes h magnitudes ( #h or m on ! ,ri*t] scale4 ,! ,modifi$ ,m]calli ,scale expresses ! int5sity ( an e>?quake's effects 9 a giv5 locality 9 values rang+ f ,i to ,,xii4 ,! mo/ commonly us$ adaptation cov]s ! range ( int5sity f ! condition ( 8,i--,n felt except by a v few "u especially favorable conditions10 to 8,,xii--,damage total4 ,l9es ( sight & level are di/ort$4 ,objects ?r[n upw>d into ! air40 ,evaluation ( e>?quake int5sity c be made only aft] eyewitness reports & results ( field inve/igations are /udi$ & int]pret$4 ,! maximum int5sity exp]i5c$ 9 ! ,alaska e>?quake ( #aifd 0 ,x2 damage f ! ,san ,francisco & ,new ,madrid e>?quakes rea*$ a maximum int5sity ( ,,xi4 ,illu/ration3 ,! ,janu>y #ag1 #aiid1 e>?quake at ,nor?ridge1 ,cali=nia1 caus$ ?is collapse ( a major highway int]*ange4 7,photograph by ,james ,w4 ,dewey1 ,,usgs47 ,e>?quakes ( l>ge magnitude d n necess>ily cause ! mo/ int5se surface effects4 ,! effect 9 a giv5 region dep5ds to a l>ge degree on local surface & subsurface geologic conditions4 ,an area und]la9 by un/able gr\nd 7s&1 clay1 or o!r unconsolidat$ mat]ials71 = example1 is likely to exp]i5ce mu* m noticeable effects ?an an area equally di/ant f an e>?quake's epic5t] b und]la9 by firm gr\nd su* z granite4 ,9 g5]al1 e>?quakes ea/ ( ! ,rocky ,m\nta9s affect a mu* l>g] area ?an e>?quakes we/ ( ! ,rockies4 ,an e>?quake's de/ructiv5ess dep5ds on _m factors4 ,9 addition to magnitude & ! local geologic conditions1 ^! factors include ! focal dep?1 ! di/ance f ! epic5t]1 & ! design ( build+s & o!r /ructures4 ,! ext5t ( damage also dep5ds on ! d5sity ( population & con/ruction 9 ! area %ak5 by ! quake4 ,! ,loma ,prieta e>?quake ( #aihi demon/rat$ a wide range ( effects4 ,! ,santa ,cruz m\nta9s suff]$ little damage f ! seismic waves1 ev5 ?\gh !y 7 close to ! epic5t]4 ,! c5tral core ( ! city ( ,santa ,cruz1 ab\t #bd kilomet]s 7#ae miles7 away f ! epic5t]1 0 almo/ completely de/roy$4 ,m ?an #hj kilomet]s 7#ej miles7 away1 ! cities ( ,san ,francisco & ,oakl& suff]$ selective b sev]e damage1 includ+ ! loss ( m ?an #dj lives4 ,! greate/ de/ruction occurr$ 9 areas :]e roads & elevat$ /ructures 7 built on un/able gr\nd und]la9 by loose1 unconsolidat$ soils4 ,! ,nor?ridge1 ,cali=nia1 e>?quake ( #aiid also produc$ a wide v>iety ( effects1 ev5 ov] di/ances ( j a few hundr$ met]s4 ,"s build+s collaps$1 :ile adjac5t build+s ( simil> age & con/ruction rema9$ /&+4 ,simil>ly1 "s highway spans collaps$1 :ile o!rs ne>by did n4 ,illu/ration3 ,a sudd5 increase 9 e>?quake tremors signal$ ! beg9n+ ( a s]ies ( eruptions at ,r$\bt ,volcano 9 #aihi-ij4 ,volcanoes & ,e>?quakes ,e>?quakes are associat$ ) volcanic eruptions4 ,abrupt increases 9 e>?quake activity h]ald$ eruptions at ,m\nt ,/4 ,hel5s1 ,wa%+ton2 ,m\nt ,spurr & ,r$\bt ,volcano1 ,alaska2 & ,kilauea & ,mauna ,loa1 ,hawaii4 ,! location & movem5t ( sw>ms ( tremors indicate ! movem5t ( magma ?r\gh ! volcano4 ,cont9u\s records ( seismic & tiltmet] 7a device t measures gr\nd tilt+7 data are ma9ta9$ at ,u4,s4 ,geological ,survey volcano obs]vatories 9 ,hawaii1 ,alaska1 ,cali=nia1 & ! ,cascades1 :]e /udy ( ^! records enables speciali/s to make %ort-range pr$ictions ( volcanic eruptions4 ,^! w>n+s h be5 especially effective 9 ,alaska1 :]e ! imm95t eruption ( a volcano requires ! r]\t+ ( int]national air traffic to enable airplanes to avoid volcanic cl\ds4 ,s9ce #aihb1 at lea/ sev5 jumbo jets1 c>ry+ m ?an #a1ejj pass5g]s1 h lo/ p[] 9 ! air aft] fly+ into cl\ds ( volcanic a%4 ,?\gh all flights 7 able to re/>t _! eng9es ev5tually & no lives 7 lo/1 ! aircraft suff]$ damages ( t5s ( millions ( doll>s4 ,z a result ( ^! close calls1 an int]national team ( volcanologi/s1 meteorologi/s1 dispat*]s1 pilots1 & controll]s h begun to "w toge!r to al]t ea* o!r to imm95t volcanic eruptions & to detect & track volcanic a% cl\ds4 ,pr$ict+ ,e>?quakes ,! goal ( e>?quake pr$iction is to give w>n+ ( pot5tially damag+ e>?quakes e>ly en\gh to all[ appropriate response to ! disa/]1 enabl+ p to m9imize loss ( life & prop]ty4 ,! ,u4,s4 ,geological ,survey conducts & supports rese>* on ! likelihood ( future e>?quakes4 ,?is rese>* includes field1 laboratory1 & !oretical inve/igations ( e>?quake me*anisms & fault zones4 ,a prim>y goal ( e>?quake rese>* is to increase ! reliability ( e>?quake probability e/imates4 ,ultimately1 sci5ti/s w\ld l to be able to specify a high probability = a specific e>?quake on a p>ticul> fault )9 a p>ticul> ye>4 ,sci5ti/s e/imate e>?quake probabilities 9 two ways3 by /udy+ ! hi/ory ( l>ge e>?quakes 9 a specific area & ! rate at :i* /ra9 accumulates 9 ! rock4 ,sci5ti/s /udy ! pa/ frequ5cy ( l>ge e>?quakes 9 ord] to det]m9e ! future likelihood ( simil> l>ge %ocks4 ,= example1 if a region has exp]i5c$ f\r magnitude #g or l>g] e>?quakes dur+ #bjj ye>s ( record$ hi/ory1 & if ^! %ocks occurr$ r&omly 9 "t1 !n sci5ti/s w\ld assign a #ej p]c5t probability 7t is1 j z likely to happ5 z n to happ57 to ! occurr5ce ( ano!r magnitude #g or l>g] quake 9 ! region dur+ ! next #ej ye>s4 ,b 9 _m places1 ! assumption ( r&om occurr5ce ) "t may n be true1 because :5 ! /ra9 is releas$ along "o "p ( ! fault sy/em1 x may actually increase on ano!r "p4 ,f\r magnitude #f4h or l>g] e>?quakes & _m magnitude #f-f4e %ocks occurr$ 9 ! ,san ,francisco ,bay region dur+ ! #ge ye>s betwe5 #ahcf & #aiaa4 ,= ! next #fh ye>s 7until #aigi71 no e>?quakes ( magnitude #f or l>g] occurr$ 9 ! region4 ,beg9n+ ) a magnitude #f4j %ock 9 #aigi1 ! e>?quake activity 9 ! region increas$ dramatically2 betwe5 #aigi & #aihi1 !re 7 f\r magnitude #f or great] e>?quakes1 includ+ ! magnitude #g4a ,loma ,prieta e>?quake4 ,?is clu/]+ ( e>?quakes leads sci5ti/s to e/imate t ! probability ( a magnitude #f4h or l>g] e>?quake occurr+ dur+ ! next #cj ye>s 9 ! ,san ,francisco ,bay region is ab\t #fg p]c5t 7twice z likely z n74 ,ano!r way to e/imate ! likelihood ( future e>?quakes is to /udy h[ fa/ /ra9 accumulates4 ,:5 plate movem5ts build ! /ra9 9 rocks to a critical level1 l pull+ a rubb] b& too tight1 ! rocks w sudd5ly break & slip to a new position4 ,sci5ti/s measure h[ mu* /ra9 accumulates along a fault segm5t ea* ye>1 h[ mu* "t has pass$ s9ce ! la/ e>?quake along ! segm5t1 & h[ mu* /ra9 0 releas$ 9 ! la/ e>?quake4 ,?is in=mation is !n us$ to calculate ! "t requir$ = ! accumulat+ /ra9 to build to ! level t results 9 an e>?quake4 ,?is simple model is complicat$ by ! fact t su* detail$ in=mation ab\t faults is r>e4 ,9 ! ,unit$ ,/ates1 only ! ,san ,&reas fault sy/em has adequate records = us+ ?is pr$iction me?od4 ,illu/ration3 ,us+ a two-color las] to detect movem5t along a fault ne> ,p>kfield1 ,cali=nia4 ,bo? ( ^! me?ods1 & a wide array ( monitor+ te*niques1 are be+ te/$ along "p ( ! ,san ,&reas fault4 ,= ! pa/ #aej ye>s1 e>?quakes ( ab\t magnitude #f h occurr$ an av]age ( e #bb ye>s on ! ,san ,&reas fault ne> ,p>kfield1 ,cali=nia4 ,! la/ %ock 0 9 #aiff4 ,because ( ! consi/5cy & simil>ity ( ^! e>?quakes1 sci5ti/s h />t$ an exp]im5t to 8capture0 ! next ,p>kfield e>?quake4 ,a d5se web ( monitor+ in/rum5ts 0 deploy$ 9 ! region dur+ ! late #aihjs4 ,! ma9 goals ( ! ongo+ ,p>kfield ,e>?quake ,pr$iction ,exp]im5t are to record ! geophysical signals be=e & aft] ! expect$ e>?quake2 to issue a %ort-t]m pr$iction2 & to develop effective me?ods ( communication betwe5 e>?quake sci5ti/s & community (ficials responsible = disa/] response & mitigation4 ,?is project has already made important contributions to bo? e>? sci5ce & public policy4 ,illu/ration3 ,san ,&reas fault 9 ! ,c>rizo ,pla91 c5tral ,cali=nia4 ,sci5tific und]/&+ ( e>?quakes is ( vital importance to ! ,nation4 ,z ! population increases1 exp&+ urban developm5t & con/ruction works encroa* ^u areas susceptible to e>?quakes4 ,) a great] und]/&+ ( ! causes & effects ( e>?quakes1 we may be able to r$uce damage & loss ( life f ?is de/ructive ph5om5on4 ,illu/ration3 ,a /atue ( ,*ri/ at ,cemet]y ,hill ov]looks ! ru9$ t[n ( ,yungay1 ,p]u4 ,x & a few palm trees 7 all t rema9$ /&+ aft] ! ,may #ca1 #aigj1 e>?quake4 ,u4,s4 ,geological ,survey ,in=mation ,s]vices ,p4,o4 ,box #bebhf ,d5v]1 ,,co #hjbbe ,u4,s4 ,,gov]nm5t ,,pr9t+ ,,(fice3 #aiif--dba-bje ,illu/ration3 ,,u ,,dep>tm5t ,,( ,,! ,,int]ior2 ,,m>* #c1 #ahdi ,z ! ,nation's pr9cipal cons]vation ag5cy1 ! ,dep>tm5t ( ! ,int]ior has responsibility = mo/ ( our nationally own$ public l&s & natural & cultural res\rces4 ,?is includes fo/]+ s\nd use ( our l& & wat] res\rces2 protect+ our fi%1 wildlife1 & biological div]sity2 pres]v+ ! environm5tal & cultural values ( our national p>ks & hi/orical places2 & provid+ = ! enjoym5t ( life ?r\gh outdoor recreation4 ,! ,dep>tm5t assesses our en]gy & m9]al res\rces & works to ensure t _! developm5t is 9 ! be/ int]e/s ( all our p by enc\rag+ /ew>d%ip & citiz5 p>ticipation 9 _! c>e4 ,! ,dep>tm5t also has a major responsibility = ,am]ican ,indian res]vation communities & = p :o live 9 isl& t]ritories "u ,u4,s4 adm9i/ration4 ,illu/ration3 7,cov] photographs1 clockwise f top left73 ,mexico ,city1 ,mexico1 #aihe2 ,coal+a1 ,calif41 #aihc2 ,nor?ridge1 ,calif41 #aiid2 ,an*orage1 ,alaska1 #aifd2 ,san ,francisco1 ,calif41 #aijf2 ,loma ,prieta1 ,calif41 #aihi4 ,transcrib]'s ,notes --,reta9$ publication in=mation f ! pr9t$ edition3 ?is e,book is public-doma9 9 ! c\ntry ( publication4 --,9 ! text v]sions only1 text 9 italics is delimit$ by und]scores4 --,9 ! ,,ascii v]sion only1 subscript$ numb]s are prec$$ by und]score & delimit$ by brackets4