Earth Quake -2

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Earthquake Prediction, Seismic Hazard And Vulnerability

S e i y a U y e d a

Earthquake Prediction Research Center, Tokai University, Shizuoka, Japan

K i m i r o M e g u r o

International Center for Urban Safety Engineering , Institute of Industrial Scien ce,The University of Tokyo, Tokyo, Japan

Mit iga t ion o f se i smic hazards requ i res in teg ra t ion o f sc ience and human ac t ion ,n a me l y t h e s c i e n c e o f e a r t h q u a k e s , a n t i - s e i s mi c e n g i n e e r i n g a n d s o c i o - p o l i t i c a lme a s u r e s . T h e p u b l i c , me d i a , p o l i c y ma k e r s a n d f u n d i n g a g e n c i e s mu s t b e c o nstant ly reminded that seismic d isas ters rapid ly escalate with civ i l izat ion 's growth andtha t d i sas te rs co m e wh en the l as t t ragedy has bee n fo rgo t t en . Lo ss o f hu ma n l i fei s cause d overwh elmi ng ly by the co l l apse o f house s and o ther bu i ld ings wi th in l es sthan a few m inu tes o f the ma in shock s . The m os t u rgen t coun te rmeasu re i s the re info rcemen t o f weak s t ruc tu res . When s t ruc tu ra l damage i s reduced , mos t o ther se i smic hazards wi l l co r respond ing ly be g rea t ly reduced . I f sho r t - t e rm p red ic t ion i smade , casua l t i es wi l l be fu r ther reduced d ramat ica l ly. Desp i t e genera l pess imism,sho r t - t e rm p red ic t ion research nee ds to be enh ance d because recen t research sh ow srea l p romise . Thus , the re in fo rcemen t o f ex i s t ing s t ruc tu res and enhancemen t o fsho r t - t e rm p red ic t ion research a re the two keys fo r se i smic hazard mi t iga t ion .

I N T R O D U C T I O N

Earthquak es are caused by sudden fault motion . I t has lon gbeen kn own that the g lobal d is t r ibut ion of earthquakes is farfrom uniform, as shown in Fig . 1 . Wh ile mid-ocea nic r id gesare characterized by l inear d is t r ibut ion of relat ively smallearthquakes , large earthquakes occur mainly in the circum-Pacific bel t and in the wide zone between Eurasia and thesouthern continents. The reaso n why they are distributed in thisman ner is explained by plate tectonics [e. g., Stein andKlo sko,2 0 0 2 ] ; large earthquakes occur due to p late in teract ions atconvergent and t ransform plate bounda ries . Convergent p lateboundaries consis t of subduct ion and col l is ion zones . Stat ist ical propert ies of earthquake occurrences in these seismiczones a re wel l -known thanks to many decades o f se i smic

The State of the Planet: Frontiers and Cha llenges in Geo phy sicsGeophysica l Monograph 150 , IUGG Volume 19Copyr igh t 2004 by the In te rna t iona l Union o f Geodesy and Geophysicsand the Amer ican Geophysica l Union .1 0 . 1 0 2 9 / 1 5 0 G M 2 7

observat ions around the g lobe, and many seismic hazard mhave been comp iled both globally and regionally [e. g., GSp r o g r a m, Giardini, 1999].

Plate tectonics has shown with reasonable certain ty p late motions have bee n essent ially s teady for the t ime-scof a few mil l ions of years , a l though they have changed much longer t ime sca les du r ing the ea r th ' s h i s to ry [eKumazawa and Maruyama, 1994 ; Uyeda, 200 2 ] . Howevthe seismici ty of the g lobe also d isplays variat ion on ftime-scales of tens of years, as shown in the upper pan el of2 . T h e d e t a i l e d me c h a n i s m s f o r t h e s e s h o r t - t e r m s e cchanges are not clear, but i t seems plausib le that there cafluctuat ions even und er s teady g lobal p late mo tions . I t sesignificant that the variations in the loss of life shown inlower panel of Fig . 2 are very d ifferent from variat ionseismicity. The reason for this is quite clear. Earthquakedensely populated regions cau se greater disasters [Utsu, 200For instance, the two largest giant earthq uake s, the 1960 MChilean and 1964 M9 .2 Alaskan earthquak es, caused mu ch

349


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350 EARTHQUAKE PREDICTION, SEISMIC HAZARD AND VULNERABILITY

Figure 1 Epicenter distribution of the world for magnitude greater than 4.0 in 1980-2000, after U SGS PDE.

loss of l i fe compared to the much smaller 1923 M7.9 Kantoand 1976 M7.8 Tangshan earthquakes . (Hereafter, M s tandsfor the magnitude of an earthquake).

Here w e review briefly the s tate of the art on seismic h azard and present personal views on the priority items related toearthquake hazard mit igat ion . Specific matters taken up inthe text are focused on Japan. However, it is anticipated thatwhat w e present will be generally applicable to all earthqua ke-prone reg ions of the world .

As well as loss of life, earthquakes cause disasters of allk inds . In terms of monetary loss , th is can amount to a substant ial fract ion of the Gross Domest ic Product (GDP) of ana t ion . Fo r the 1995 Kobe ear thquake , mone ta ry lo s s wasestimated at 10 billion US dollars and for the Tonank ai-Nankaievent , which is a major ant icipated fu ture earthqu ake, i t mayamount to at least 80 billion US dollars, which would be morethan 15% of the GDP accord ing to the Central Disas ter Management Counci l of Japan. Since bui ld ings in Japan are nowmore seismic resistant than in the past, loss of life in largeci t ies may be less than those in the past . However, huge damage of complicated life-lines and infra-structures can still beexpected in modern mega-ci t ies when they are h i t by majorquakes . Further many meg a-ci t ies in the developing world donot have good adherence to bui ld ing codes and so there canbe huge loss of life as illustrated by the 2004 Bam earthquake

in Iran. Seismic risk rapidly escalates with population growthand the disasters com e whe n the last experience is forgotten .

F I R S T P R I O R I T Y I S T H E R E I N F O R C E M E N TO F O U R H O U S E S

Many problems arise at and after a d isas trous earthquake[Meguro and Takahashi, 200 1 ] , inc lud ing :

1) Loss of life at the time of the main shock,2) Further v ict ims due to f i res ,3) Psychological ins tabi l i ty of people in the affected ar4) Disru pt ion of the comm unity,5) Building refugee camps for large number of displaced

ple ,6) Demol i t ion o f damaged s t ruc tu res and re la ted env i

mental effects,7) Economic, business and societal d isrupt ion .

At the time of the main shock , rapid delivery of inform aon ground m otions and dam ages to the authori t ies and puare cri t ical ly important for rescue act iv i ty. Thanks to madvances in information technology, there is an emerging category of hazard mit igat ion; real- t ime seismology thatbeen developed in several areas , including Japan, MexCalifornia and Taiwan [e. g., Nakamura, 1988; EpinosaAranet al, 1995 ; Kanamori et al, 1997 ; Shin et al., 2000 ] . TSeismic Alert System in Mexico made use of the gap ofarrival times of the P- and S-waves. The authorities were to issue t imely alarm s so that the subways in the Mexic o were s toppe d 50 seconds before the arrival of the destrucS-waves from the 1995 M7.3 Guerrero earthquake locatethe Pacific coast. However, many of the problems listed abwill last for a long time after the event. To cope with the lu t ion of d isas ter s i tuat ions in hours , days , weeks and

months , innovat ive engineering s t rategies wil l be needenew kind of s t rategy can be cal led the real- t ime earthquengineering . After the main shock, cont inuing data col leof s t ructure damage d is t r ibut ion , rescue act iv i t ies , l i fein te r rup t ions , deb r i s removal , re fugee camps , and podemand f luc tua t ions and o ther paramete rs wi l l be c r i tbecause o f the u tmost im portance for d isas ter rel ief agenand local and national govern ments to allocate resources in


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UYEDA AND MEGURO 35

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Figure 2 Secular variations of seismic energy release (upper panel) and human loss (lower panel). Ordinate of the upperpanel represents the size of earthquakes in seismic moment M 0, seismic energy E and the mom ent magnitude Mw. Ordinate of the lower panel shows the number of victims. In both panels, the vertical b ars are for individual event and thesolid curve shows the annual average (untagged 5-year running average) (after H. Kanamori, private communication).

mos t p rompt and efficient m anner [Noda and Meguro, 1995;Hada and Meguro, 2002] .

W e now focus i tems 1) and 2) in the above list, namely onhow to save huma n l i fe . Experiences all over the world sho w

Other places8 . 5 %

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Hospital3 . 8 %

O w n h o u s e s86.6 %

Figure 3 . Places where people died (in Kobe City), (after N ishimuraet al., 1997b)

that , a lmost without except ion , the majori ty of v i c t ims arkil led by the col lapse of bui ld in gs r ight at the mom ent of tmain shock (Plate 1, a & b ) . An example is shown in Fig . 3 fothe 1995 M7.3 Hyog oken Nanbu Earthquake, which took5,500 human l ives . (This earthquake is commonly ca l led thKobe earthquake after the name of the city, where the damwas most in tense.) Alm ost 90 of the v ict ims were k i l led their own houses. Moreover, medical examinations indicate92 of casual t ies were k i l led with in less than 15 minu tafter the quake befo re any o rgan ized rescue opera t ion hastarted [Nishimura et. al., 1997a, b].

M a n y v i c t i m s of e a r t h q u a k e s can be k i l l e d by f i reAl though f i res can be caused by shak ing , mos t of b ig f i rs tart from col lapsed houses . Fires that s tarted in n o n - c ol a p s e d h o u s e s w e r e c o mmo n l y e x t i n g u i s h e d by the r e sdents , while those that s tarted in co l l apsed houses were noResidents under debris could no t fight th e fires and the f

p r io r i ty of ou t s ide rescuers was to get t h e m out from thfa l l en houses . Fu r thermore , roads were o f ten b locke f i re engines by co l lapsed hou ses . In K o b e , th e F i re D epam e n t had a capac i ty to h and le on ly th ree to four f i res at t ime . When many tens of f i res s tarted s imultan eously, thwere completely ove rwhelm ed. To prevent f i res from deo p i n g to u n c o n t r o l l a b l e s i z e , th e b e s t way is to p r e v ehouses from col lapsing.


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3 52 EARTHQUAKE PREDICTION, SEISMIC HAZARD AND VULNERABILITY

Plate 1 . Dam age to low earthquake resistant structures is major cause of casualties and many problems gene rated afterthe earthquake in the world (photo by K. M eguro) (a) Damage to old timber houses due to the Kobe earthquake (M 7.3)1995 in Japan (b)Damage to m asonry houses due to the Qayen earthquake (M 7.1), 1997 in Northeast Iran.

If the governm ent of Japan were to fund 10 b i l l ion US dollars annual ly, a l l the necessary reinforcement of houses inJapan wou ld be comple ted in t en years [Ohtake, 20 03 ] . Inorder to implement the house reinforcement program effect ively, the fo l lowing system, cal led the Retrofi t t ing Promotion System, has been proposed [Meguro and Takahashi, 2 0 0 1 ;Yoshimura and Meguro, 200 3]. The main concept of th is system is that the governm ent guara ntees to pay a port ion of therepair and reconstruct ion expenses of damaged houses provided that proper retrofi t t ing had been implemented by theowners before the earthquake. With such a system, the overal l f inancial bur den of both governmen t and res idents can be

great ly reduced . The feas ib il i ty of th is system has been verified for cases in which the retrofitting cost is 10 to 15 % of thenew construction cost, as is the case in Japan. However, forcountries l ike Turkey, where the retrofi t t ing cost am ounts toapproximately 75% of the new construct ion cost , the systemis not viable. In such cases, efficient and economic techniquesfor retrofitting are needed, especially for masonry structures,using locally available and inexpensive materials [Mayorca andMeguro, 2 0 0 3 ] .

If the s t ructural damage is reduced, loss of human l i fe isreduced. Thus, the most effect ive and h ighest priori ty coun-termeasure against the loss of human l i fe , and al l k inds ofrelated seismic hazards and consequences , is the s t ructuralissue. In the recent December 26 , 2 0 0 3 , M6 .7 Bam Ear thquake in Iran , there were more than 30,000 casual t ies due tothe col lapse of adobe and brick s t ructures which lacked reinforcement . After the d isas ter, in ternat ional and local agencies rushed to the affected s i tes t ry ing to rescue survivors .Althou gh these were valuable efforts , only a few peo ple surv ived and were rescued , aga in h igh l igh t ing the qua l i ty o fbui ld ings as a key issue.

F I R S T P R I O R I T Y I N S C I E N C E I S S H O RT- T E RP R E D I C T I O N

Engineering seismology and earthquake predict ion tu te the two key measu res that need imp lementat ion foseismic hazard mit igat ion . I t is customary to class ifyquake predict ion in to three categories : long-term, in tea te - t e rm and sho r t - t e rm p red ic t ions . They a re d i ffemethodology , accuracy and purpo ses . For the purpose ing human l i fe , the short- term (less than a day to mpredict ion is most effect ive. If people had been waradvance and had escaped adobe bui ld ings in t ime, cas

in the recent Bam earthquake could have been manysmal le r. The impac t o f sho r t - t e rm p red ic t ion on caswould also be dramatic for cases of large earthquakgenerate tsunamis .

Long-term predict ion deals with the probabi l i ty ofquake occ urren ce on t ime-scales of 10 to 100 years ,mainly on geologic s tudies of faul ts and h is toric recoseismici ty, while in termediate-term (1 to 10 years) preuses more recent data including seismological observOne of the most advanced of such efforts is the M8 algwhich is based on the non-l inear dynamics (Keilis-BorokKossobokov, 1990). I t is a pat tern recognit ion approachon monitoring seismici ty and i ts f luctuations . Lon g anmediate-term predict ions are typical ly s tat is t ical l ikeest imates , while short- term predict ion is based on somini te precursors .

Systematic short-term earthquake prediction research in the 1960's in several countries including Japan, US A,Union, and China [Rikitake, 1976]. In the 1970's, optimismvai led due to the encou rag ing deve lopmen ts , such atancy models [e . g . , Scholz et al, 1973] and the succ


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UYEDA AND MEGURO 35

predict ion of the 1975 M7.2 H aisheng ea rthquake in China[Chen et al., 1990; Li Hui 1996 ]. However, n o further generally recognized successes followed, causing the community tobec om e pess imis t ic . Apparent ly, the fai lure of predict ing theearthquak e in Parkfield, C alifornia [Andrews, 1992], where theWorld ' s bes t mon i to r ing sys tem was in opera tion , d i scou raged American researchers. This is understandable but today'swidesp read pess imism seems t o be unjust i f ied b ecause sucha v iew misses the point that both science and techno logy aremaking rapid progress .

In 197 8, the Earthquake Pred ict ion Progra m of Japan designated eight areas of special obser vat ion and two areaso f in tens i f ied observa t ion ( in se t of Fig . 4) , based on h i storical ly d isas trous earthquakes , act ive faul ts , h igh seismicit y an d soc io -economic impor tance [Hamada, 1992 ]. Thiscan be taken as an example of se t o f n a t ionwide in te rmed iate-term predict ions . Comp aring the two maps in Fig . 4 indicates that the in termediate-term predict ions have been more

or less fulfilled, because most of the large earthquakes after1978 have occurred i n o r near the areas o f special o bservat ion . However, none of t hese ea r thq uakes , inc lud ing theKobe earthquake, was predicted in the short- term. The mainreason for th is was that the methods for short- term predict ionwere not applied in any of these areas of special observation .In fact, the me thods , such as densely d is t r ibute d t i l t -m eterand strain-meter monitorin g, have been app lied only in the two

areas of in tensif ied observ at ion where major earth quak eshave not yet occurred . The two areas of in tensif ied obser

va t ion were se lec ted because a g rea t ea r thquake exceedma g n i t u d e 8 is expec ted to occur there soon, based on loterm predict ion s . This fu ture earthqu ake has even been ga n a me : th e Toka i (m ean ing Eas t Sea in J a p a n e s e ) e a rquake. The postulated epicentral area has lately been extenwestw ard as in the main m ap of Fig . 4, so that it is now ofcal led th e Tonanka i /N anka i (Eas t Sou th /Sou th Sea) eaquake (see Fig . 6).

When people assert that the search for ea r thquake p recsors has proven useless , they often overlook the fact thaten t i f i c an d e ffec tive p recu r so r re search has s e l d o m b ecarried out . Certain ly, seismic network s have been consiab ly upg raded , so t ha t even micro -ear thquakes can now bd e t e c t e d and l o c a t e d p r e c i s e l y. P r e c u r s o r y c h a n g e s local/regional seismicity, such as fore-shock activity and escence , may be d e tec ted [e. g., Sobolev et al., 2 0 0 2 ] , buseismic networks are n ot suited, b y defin i t ion , for detect inon-seismic precursors .

Wh en an ea r thquake occu rs , it is a mech anical v ibrat ionthe ground but s ince it is caused by b reak ing of the eartcrust , which , unl ike f lawless p iece of g lass , has h ighly herogeneous structures, it is reasonable to expect that its preptory process has various facets which may be o bserved bethe f inal catas trophe. Therefore, th e s c ience of ea r thquapredict ion should be mult id iscip l inary as depicted in F ig . In seismology, the s tudy of the physical mechanism s of eaquake generation has made significant advances, which inct h e e a r t h q u a k e d y n a mi c s mo d e l s w i t h p r e - s e i s mi c s l

Areas ofI : special observation : intensified observation

M7.3, 2000

M6.4, 2001

M6.5, 1997

M7.8, 1993

M7.5 8 Off Mi yagi ken

M8 Tokai

MS Nankai/Tonankai

Figure 4 . Inset shows the eight areas for special observatio n (empty rectangles) and two areas for intensified observation(filled rectangles), selected by the Japanese Earthquake Prediction Program in 1978. Main figure shows the roughly estimated source regions of major earthquakes which occurred afterwards (smaller letters) and expected earthquakes (largerletters).


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UYEDA AND MEGURO

36 - 1 1 1 1 1 h20 21 22 23 24 25 26E

Figu re 7. Evaluation of VAN prediction. All the earthquakes withUSGS PD E magnitude larger than 5.5 for 1 985-2 003. Earthquakesare specified next to each circle. For example, 950513 mb 6.1 meansyear (1995), month (M ay), day (13th) and magnitude 6.1. The symbol mb is body wave magn itude.Shaded circles: successfu lly predicted.White circle with triangle: unsuccessfully predicted.White circles: missed.

electr ic currents in the earth . Fig . 7 shows some resul ts oftheir method, now ca lled the VAN m ethod (after the initials ofthe mem bers of the founding team) [e . g . , Nagao et al, 1996;Uyeda andAl-Damegh, 1999, Uyeda etal, 1999; Kondo etal,2 0 0 2 ] . For the period 1985-2003, 12 out of 16 M=5.5 earthquakes in the Greek region were successfully predicted . Successful prediction her e mean s that the errors were less than 0.5for earthquake m agnitu de, 100 km in epicentral posi t ion a nda few weeks in date. The publ ic im pact of VAN 's predict ion shas been quite large becau se citize ns' lives have bee n saved atd isas trous earthquakes [Uyeda, 2000 ] .

In Japan , s evera l research g roups have worked on ea r thquake re la ted e lec t romagne t ic phenomena s ince the ea r ly1990 ' s . At the t ime o f the Januar y 17 , 1995 Kob e e a r thquake , anomalous e lec t romagne t ic phenomena a t f requenc ies rang ing f rom ex t remely low f requency (ELF; 102 103

Hz) to very h igh frequency (V HF ; ~1 02 MHz) were observedat many local i t ies [Nagao et al, 200 2 ] . Encouraged by theser e s u l t s , s e i s m o - e l e c t r o m a g n e t i c r e s e a r c h i n J a p a n h a sbecome very ac t ive . Th rough dep loy ing abou t 40 mon i to ring s tat ions for the geoelectr ic potent ial changes over thecoun t ry, i t was demons t ra ted tha t the VAN-type p re -se i s -

mic changes also occur in Japan [Uyeda et al, 2 0 0 0 ] . T hw e r e o b s e r v e d b e f o r e M > 5 e a r t h q u a k e s t h a t o c c uwith in 20 k m or so of our s tat ions (Fig . 8) . Clear co-seis igna l s , synch ron ized wi th the a r r iva l o f s e i smic wahave a l so been observed fo r nearby ea r thquakes [Nagao al , 2 0 0 0 ] .

Pioneering work has also been made on the precursory nomena in the u l t ra low frequency (ULF: 0 .01 Hz) geomnetic f ield variat ions . Notable examples are the 1988 MS p i t a k [Kopitenko et al, 1993 ] , 1989 M7 .1 Lo ma Pr i[Fraser-Sm ith et al, 1990 ] , 1993 M8 .0 Guam [Hayakawa al , 1996 ] and 1997 M6 .5 Kagosh ima ear thquakes [Hattoetal, 2 0 0 2 ] .

Fig . 9 is the g lobal summary of the ULF invest igat ishowing the empirical relat ionship between earthquake mnitude and epicentral d is tance. White and b lack marks sthe earthquakes with and without observed ULF anomarespect ively. The s lant l ine indicates the empirical es t im

of the th resho ld fo r the appearance o f ULF s igna l s . in s tance , ULF s igna l s o f M7 ear thquake wi l l be de tewithin 100 or so km from the epicenter.

In the summer of 2000, there was a large swarm act iin the Izu island region south o f Tokyo. In this case, both etr ic f ield and magnet ic f ield measured at far apart s tat

130E 140E 150E

130E 140E 150E

Figure 8 Distribution of M > 5 earthquakes w ith pre-seismic siduring the period before March 1999. Diamo nds and circles shpre-seismic electric signals and U LF m agnetic signa ls, respectiStars showed both electric and magnetic signatures. EQ 98/0M6.1 means M6.1 earthquake which occurred on September 3,1


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356 EARTHQUAKE PREDICTION, SEISMIC HAZARD AND VULNERABILITY

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Earth Quake -2