1.1. Ingenieria Sismologica

7/25/2019 1.1. Ingenieria Sismologica

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INGENIERIA SISMORRESISTENTEFundamentos de Sismologa e Ingenieria Sismolgica

M.I. Jos Velsquez VargasMaestra en Ing. Sismorresistente e Ing. Sismolgica (Rose School, Italia)


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Terremotos

Terremoto de Pisco (15/08/2007)

Fuente: Informe de terremotos ocurridos en el mundo - Colegio de Ingenieros del Per

Terremoto de Chile (27/02/2010)

Terremoto de Hait (12/01/2010)

Terremoto de Japn (11/03/2011)


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Terremoto de Ecuador (2016)

Terremoto de Manta Mw 7.8 (16/04/2016)

Fuente: http://earthquake.usgs.gov/


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Qu es un terremoto?Son vibraciones de la corteza terrestre, generadas por distintos fenmenos, comola actividad volcnica, la cada de techos de cavernas subterrneas y hasta porexplosiones. Sin embargo, los sismos ms severos y ms importantes desde elpunto de vista de la ingeniera, son los de origen tectnico.

Placas que conforman la

corteza terrestre


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SISMICIDAD GL0BAL

95% de la energa liberada por terremotos se originan en regionesestrechas alrededor de la Tierra: estas zona marcan los bordes delas placas tectnicas

Sismicidad global entre 1975-1999 conterremotos de magnitude mayor a Mw5.5


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Cinturn de Fuego del PacficoEst situado en las costas del ocano Pacfico y se caracteriza por concentraralgunas de las zonas de subduccin ms importantes del mundo, lo que ocasionauna intensa actividad ssmica y volcnica en las zonas que abarca.Con ms de 450 volcanes concentra ms del 75 % de los volcanes activos einactivos del mundo. Alrededor del 90 % de los terremotos del mundo y el 80 %de los terremotos ms grandes del mundo se producen a lo largo del Cinturn deFuego.


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Qu es un terremoto?La presiones que se generan en la corteza por los flujos de magma desde elinterior de la tierra llegan a vencer la friccin que mantienen en contacto losbordes de las placas y producen cadas de esfuerzo y liberacin de enormescantidades de energa almacenada en la roca. La energa se liberaprincipalmente en forma de ondas vibratorias que se propagan a grandesdistancias a travs de las rocas de la corteza.


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major eqs 8

LOS TERREMOTOSMS GRANDESDESDE 1900


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CLCULO DEL PELIGRO SSMICO

0.1

1

10

3.7 4 4.3 4.6 4.9 5.2 5.5 5.8 6.1 6.4 6.7 7 7.3 7.6 7.9

ZS 63 1936-1980

1915-1980

1895-1980

1843-1980

1787-1980

1626-1980

1501-1980

1300-1980

1000-1980

Scelta

Numeronormalizzato

(100anni)

Magnitudo

7.0008, 0.18595

0.1

1

10

3.7 4 4.3 4.6 4.9 5.2 5.5 5.8 6.1 6.4 6.7 7 7.3 7.6 7.9

ZS 63 1936-1980

1915-1980

1895-1980

1843-1980

1787-1980

1626-1980

1501-1980

1300-1980

1000-1980

Scelta

Numeronormalizzato

(100anni)

Magnitudo

7.0008, 0.18595


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MAPA DE PELIGRO SSMICO DE PAKISTAN


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Movimientodelasplac

as

tectnicas

Zona dedivergencia

Zona de fallas

Zona de

convergencia


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Zona de divergenciaSe generan cuando las placas van en direcciones opuestas, por lo tanto seseparan. Al separarse dejan el camino abierto para que ingrese el magma desdeel centro de la tierra. Como la mayora de las zonas de divergencia estn bajo lasuperficie el magma al entrar en contacto con el agua se enfra y genera uncuerpo slido, una roca.

En esta zona casi no se producen sismos de gran relevancia.


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Zona de fallasSe producen cuando las placas van en direcciones opuestas pero paralelamente,es decir, se rozan de lado a lado. Producen sismos menores y actividad volcnicacasi nula.

Desde San Francisco (EE. UU.) hasta la pennsula de Baja California en Mxico,es una zona de falla.


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Zona de convergenciaSon zonas en donde dos placas tectnicas se dirigen al mismo lugar, por lo tantocolisionan, dando lugar a las zonas de subduccin. La placa ms densacomienza a penetrar debajo de la placa menos pesada, se produce entonces unazona de contacto directo entre ambas placas que genera gran cantidad de sismosy actividad volcnica. Generalmente son las placas ocenicas las que se hundenbajo las placas continentales.


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Sismo histrico

Megaterremoto registrado en Chile (Valdivia) el 22/05/1960, con una intensidad de 9.4 en la escala

de Richter. Es considerado el peor terremoto en la historia de la humanidad


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FALLAFractura en la roca que desarrolla

un desplazamiento relativo

Falla pordeslizamiento:el sentido prinicipal delmovimiento en el plano defalla es horizontal

Falla por inmersin:

el sentido principal delmovimiento en el plano defalla es vertical

Falla Emerson en California:Produjo el terremoto de Landers


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Fallas por inmersin (dip-slip)

Se producen desplazamientos verticalos a lo largo del plano defalla.

90 inclinacin es vertical. a lla n orm a l: cuando la roca en el lado del plano de la falla

colgante (muro colgante) se desliza hacia abajo

a ll a i nv e rs a: cuando el muro colgante se desplaza hacia arribasobre el muro de apoyo.

Unafa l l a d e e m pu j e es un tipo especial de falla inversa en elcual el ngulo de inclinacin es pequeo (superficial). Zonas desubduccin (Cascadia en el Pacfico Noroeste) son zonas deterremotos con este tipo de fallas

NormalInversa


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earth & earthquakes 18

Fallas de

Inmersin


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Source: John S. Shelton

FALLA NORMAL: MURO COLGANTEABAJO

Plano de falla


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FALLASNORMALES


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REVERSE FAULTS


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Origen de losterremotos

Posicin originalSIN DEFORMACIN

Almacenamiento de energaDEFORMACIN PROGRESIVA

Ruptura con emisin de energa: TERREMOTORDESPLAZAMIENTO PERMANENTE


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Teora del Rebote Elstico

Harry Fielding Reid postul que lasfuerzas que causan los terremotosestn muy distantes de la fuente delterremoto. El terremoto es el resultadodel rebote elstico de la energa de

deformacin almacenada en las rocas acada lado de la falla.

Luego del terremoto de San Francisco en 1906 (California), una huella de

falla fue descubierta que tena un recorrido en lnea recta de 430 km. Eldesplazamiento relativo de la Tierra en un lado con respecto al otro de lafalla fue de 7 m.


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Rebote Elstico

Mecanismo de los terremotos

Las rocas a cada lado de la falla son deformadaspor fuerzas tectnicas.

Las rocas se flexionan y almacenan energa de

deformacin. La friccin que mantienen unidas a las rocas es

superada por las fuerzas tectnicas.

El deslizamiento se inicia en el punto ms dbil (elfoco)

Los terremotos ocurren mientras la roca

deformada vuelve a su posicin de equilibrio(rebote elstico)

El movimiento mueve las rocas vecinas y assucevisamente


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Rplicas

-El cambio en los esfuerzosque sigue al movimientoprinicipal crea terremotosms pequeos que sedenominan replicas.

Terremoto y rplicasTennessee en 1811/1812


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Terremotos en zonas de subduccin

Ejemplo recient: Sumatra Mw9.0 (terremoto y tsunami)

S C SCO Q 8


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SAN FRANCISCO EARTHQUAKE APRIL 18,1906

Fault trace 2 miles north of the Skinner Ranchat Olema. View is north.

Fence offset by the causative fault on ranch ofE.R. Strain, 1 1/2 miles north of Bolinas Lagoon,looking northeast. The sheer offset is 8 1/2 feet;the total displacement, shown partly by crookingof fence, is 11 feet.

Example of a strike-slip fault


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ALASKA EARTHQUAKE OF MARCH 27, 1964

Example of a thrust fault

Hanning Bay fault scarp on Montague Island,looking northwest. Vertical displacement in

the foreground, in rock, is about 12 feet. Themaximum measured displacement of 14 feetis at the beach ridge near the trees in thebackground.

Hanning Bay fault on MontagueIsland, looking southwest from thebay. The fault trace on the ridge ismarked by active landslides.


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SAN FERNANDO EARTHQUAKE OF FEBRUARY 9,1971

Example of a reverse fault

Trace of the main reverse fault where itcrosses Little Tujunga Road. By the timethis photograph was taken a dirt ramp atright had been built up the scarp. Thescarp indicates more than 1-meterreverse dip-slip movement. The fenceindicates little strike-slip displacement atthis place, which is near the last end ofthe line of surface rupture.

Compression of freeway


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MAGNITUD

La magnitud mide la fuerza del sismo.Es proporcional a la energa elstica liberada por el terremoto.

Se mide en base a la amplitud de onda en el sismograma considerando ladistancia epicentral.Las escalas ms comunes son:

1) Magnitud original para sismos locales obtenida a partir delsismmetro de torsion estndar de Wood-Anderson indicado como ML oMAW de acuerdo con la nomenclatura de Karnik (1976);

2) Magnitud a partir de ondas de cuerpo obtenida usandoinstrumentos de perodo corto o perodo largo, para distanciasepicentrales mayores a 1800km, llamada mB si se ha derivado a partir deperodos largos y mb si se ha derivado a partir de perodos cortos. Sedenominan MPV and M, respectivamente, de acuerdo a la nomenclaturade Karnik3) Magnitud a partir de ondas de superficie registrada por

instrumentos de perodo largo, para distancias epicentrales de ms de2200 km, indicada como MS, o MLH de acuerdo a la nomenclatura deKarnik.

Tambin hay una magnitude calculada a partir de la duracin del registro o delmovimiento local.


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MAGNITUDE

Kanamori (1977) desarroll una escala de magnitud estndar que es independientedel tipo de instrumento. Se denomina magnitud momento, indicada con M o M

W,

y se calcula a partir del momento ssmico M0.

M0

= A d

Donde es el modulo de corte de la roca con la falla (alrededor de 3.31010

N/m2), A es el rea de la falla (i.e.: el producto de su longitud por su ancho), y des el desplazamiento promedio de la falla (i.e.: deslizamiento el cual es la longituddel vector de deslizamiento de la ruptura medida en el plano de la falla).La manera estndar de convertir el momento ssmico a una magnitud (Hanks yKanamori, 1979) es:

7.105.1

log 0 = M

Mw

DondeM0 est en dina-cm.


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Magnitud localEl concepto de magnitud fue introducidopor Richter (1935): la magnitud de

cualquier sismo se toma el logaritmo dela mximo trazo de amplitude con el cualel sismmetro estndar de torsionregistara un sismo a una distanciaepicentral de 100 km.

ML =logA logA0

Charles F. Richter (1900-1985)


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instrumental seismology 33

DURATION MAGNITUDE

There is also a magnitude calculated from the duration of the recording of alocal shock: the equation has to be derived empirically by comparison withactual ML estimates. Duration magnitude is indicated with MD and thegeneral relation has the form:

where is the duration of the signal, computed from the P-wave arrival tothe moment when the earthquake wave amplitude has the same amplitudeas the background noise, is the epicentral distance anda,b, andc areparameters calculated by regression analysis. In practice,c is very small

indicating a slight dependence ofMD on distance.

MD =a +b log+c


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BODY-WAVE MAGNITUDE

The general formula recommended fromthe IASPEI's Committee of Zurich 1967is the following, given by Gutenberg in1945:

whereA is the maximum true amplitudeand T the period of the used wave, Q is

the Gutenberg-Richter's correction valuefor hypocentral depth and distance and is the station correction obtained bystatistical analysis of the resultingsystematic divergences.

m =log AT max+Q+


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SURFACE-WAVE MAGNITUDE

The magnitude from surface waves can also be computed using different waves andvertical or horizontal components. The most common is the one computed with the

waves of maximum amplitude having period from 10 to 30 seconds. The magnitudeexpression, given by Karnik (1962) is:

whereA is the maximum true amplitude of the wave used, computed as the square rootof the sum of the squares of the two horizontal components, Tis the period and dis the

epicentral distance in degrees.

M=log A

T

max+1.66log d+3.3


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SUMMARYABOUTMAGNITUDES


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COMPARACIN

Mw no se satura


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Magnitud e Intensidad de un terremoto

Magnitud: La magnitud de un sismo corresponde a la energa liberada por larotura o el desplazamiento de rocas en el interior terrestre. Se mide mediante la escalade Richter; es una escala objetiva porque se basa en los datos extrados del registro desismgrafos.

Intensidad: La intensidad de un sismo corresponde a los efectos producidos porla accin de las ondas superficiales. Se puede medir mediante la escala MSK omediante la escala de Mercalli. Las dos son medidas subjetivas porque dependen de laapreciacin de las personas


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ESCALA RICHTER (Se expresa en nmeros rabes)Representa la energa ssmica liberada en cada terremoto y se basa en el registrosismogrfico.Es una escala que crece en forma potencial o semilogartmica, de manera que cada punto

de aumento puede significar un aumento de energa diez o ms veces mayor. Una magnitud4 no es el doble de 2, sino que 100 veces mayor.


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ESCALA MERCALLI Se expresa en nmeros romanos.Creada en 1902 por el sismlogo italiano Giusseppe Mercalli, no se basa en losregistros sismogrficos sino en el efecto o dao producido en las estructuras y en lasensacin percibida por la gente. Para establecer la Intensidad se recurre a larevisin de registros histricos, entrevistas a la gente, noticias de los diarios pblicos

y personales, etc. La Intensidad puede ser diferente en los diferentes sitiosreportados para un mismo terremoto (la Magnitud Richter, en cambio, es una sola) ydepender de:a)La energa del terremoto,b)La distancia de la falla donde se produjo el terremoto,c)La forma como las ondas llegan al sitio en que se registra (oblicua, perpendicular,etc,)d)Las caractersticas geolgicas del material subyacente del sitio donde se registra laIntensidad y, lo ms importante,e)Cmo la poblacin sinti o dej registros del terremoto.


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seismic hazard 41

ESTIMACIN DEL PELIGRO SSMICO

DSHA PSHA Elementos del

PSHA

Mapas Parmetro de

movimiento


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seismic hazard 42

RIESGO= PELIGRO* VUNERABILIDAD* VALOR

RIESGO= probabilidad de observer cierto estado de dao o prdida deopercin

PELIGRO= probabilidad de observar cierto movimiento del suelo(aceleracin, intensidad, etc.)en un perodo de tiempo fijo

VULNERABILIDAD= tendencia del objeto de studio (edificio, complejo, etc.)

a sufrir daos o modificaciones

VALOR = (econmico, social, etc.) cuantificacin del objeto de estudio


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43

MODELOS ESTADSTICOS

Determinismo = el proceso ES CONOCIDOy es possible escribir una ecuacin

Ejemplo: ley de la gravedad s = 1/2 g*t2

Probabilismo = el proceso NO ES CONOCIDOy es posible aproximarlo a partir deobservacionesEjemplo: una encuesta


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seismic hazard 44

APPROACHES FOR SHA

SEISMIC HAZARD ASSESSMENT

Historical determinism

Historical probabilism

Seismotectonic probabilism

Non-Poissonian probabilism

Eq prediction

Reference ground motion

Detailed scenario

Probabilistic approaches Deterministic approaches

Muir Wood (1993)


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seismic hazard 45

DETERMINISTIC APPROACH

Select a small number of individualearthquake scenarios: M, R (Location) pairs

Compute the ground motion for eachscenario (typically use ground motion with50% or 16% chance of being exceeded if theselected scenario earthquake occurs

Select the largest ground motion from any ofthe scenarios


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seismic hazard 46

PROBABILISTIC APPROACH (1)

Source Characterization Develop a comprehensive set of possible scenario

earthquakes: M, R (location) Specify the rate at which each scenario earthquake (M, R)

occurs

Ground Motion Characterization Develop a full range of possible ground motions for each

earthquake scenario (=number of std dev above or belowthe median)

Specify the probability of each ground motion for eachscenario


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seismic hazard 47

PROBABILISTIC APPROACH (2)

Hazard Calculation Rank scenarios (M,R, ) in order of decreasing severity of

shaking

Table of scenarios with ground motions and rates

Sum up rates of scenarios (hazard curve)

Select a ground motion for the design hazard level Back off from worst case ground motion until the sum of the

rates of scenarios exceeding the ground motion is largeenough to warrant consideration (e.g. the design hazardlevel)


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seismic hazard 48

STEPS OF THE DETERMINISTIC

APPROACH

1. Identification and characterization of all earthquakesources capable of producing significant groundmotion at the site.

2. Selection of a source-to-site distance parameter for

each source zone. In most DSHAs, the shortestdistance between the source zone and the siteof interest is selected.

3. Selection of the controlling earthquake (i.e., theearthquake that is expected to produce thestrongest level of shaking), generally expressedin terms of some ground motion parameter, atthe site.

4. The hazard at the site is formally defined, usually interms of the ground motions produced at the siteby the controlling earthquake. Its characteristicsare usually described by one or more groundmotion parameters obtained from predictiverelationships.


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seismic hazard 49

CALCULO DEL PSHA

SEISMIC HAZARD ASSESSMENT

Probabilistic Approaches

Historical DeterminismHistorical ProbabilismSeismotectonic ProbabilismNon-Poissonian ProbabilismEarthquake Prediction

(Muir-Wood, 1993)

Deterministic Approaches

Reference ShakingDetailed Scenario

EL PRIMER MAPA DE


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50

EL PRIMER MAPA DEPELIGRO SSMICO (?)

Mapa de ocurrencia de terremotos

por Robert Mallet en 1854

2ND GENERATIONGumbel approach (1)


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seismic hazard 51

HISTORICALPROBABILISM

P[Imax i]= ImaxF (i) = exp{[(w i) /(w u)]k}

XF (x) = i /(n +1)

iy = ln{ln[ XF (xi)]}

iy =(xi u)

The Gumbel approach

Given Imax = max Xi, with i=1, , n and n largeType 1: no upper limit of Xi

ApplicationPutting

P[Imax i] =FImax (i) =exp[e iu( )]

Type 3: upper limit of Xi

Introducing the reduced variable

Gumbel approach (1)

2ND GENERATION HISTORICALPROBABILISM

Gumbel approach (2)


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seismic hazard 52

PROBABILISM

Example of the Gumbel approachGiven an eq catalogue, lets take the maximum annual (extreme)magnitudes and order them x1, x2, , xn: xi xi+1 i

XF (x) =i/(n +1) lets assign the annual non exceedence probability:

iy = ln{ ln[ XF (xi)]} lets calculate the Gumbel reduced variable:

iy = (x i u) we obtain:

lets compute and u by regression analysis:

lets compute the hazard estimates(e.g.: extreme exceeded with probability p in T years:

p ,Ty =u {ln[ ln(1p)] +lnT}/

Gumbel approach (2)

2ND GENERATIONHISTORICAL Th th d i i it h (1)


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seismic hazard 53


i =nje

ij2

/ c2

j

e

ij2 / c 2

j

(u >u0) =1

Ti

i

P[u >u0mmin

mu

| di,mj]fm(m)dm

The smoothed seismicity approach

The hazard computation is based on the number niof earthquakeswith magnitude greater than Mref in each cell iof a grid: this countrepresents the maximum likelihood estimate of 10a for that cell.The grid of nivalues is then smoothed spatially by multiplying by aGaussian function with correlation distance c, obtaining :

The annual rate (u>u0) of exceeding ground motion u0 at aspecific site is determined from a sum over distance and magnitude

fm(m) =b ln10 10b(mm 0)

110b(mum 0)

P[u > u0 | di,mj] =1

2

ln u0 ln u(di ,mj)

2

where

(from Frankel, 1995 andLapajne et al., 1997)

The smoothed seismicity approach (1)

2ND GENERATION


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seismic hazard 54

HISTORICALPROBABILISM The smoothed seismicity approach (2)

Options: the activity rate can be computed considering different seismicity models; the b-value and Mmax can vary in space;

different attenuation relations can be used.

Seismicity models: m0 = 3, low seismicity contributes to define hazard

(activity rates normalized over different Tsaccording to the zone)

m0 = 5, only high seismicity contributes to define hazard(activity rates normalized over different Tsaccording to the zone)

2ND GENERATION:HISTORICAL The smoothed seismicity approach (3)


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seismic hazard 55


The smoothed seismicity approach (3)

Zonation modelsin each zone b-value and Mmax are constant

Average PGAwith T=475 fromzonation models


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seismic hazard 56

3RD GENERATIONSEISMOTECTONIC PROBABILISM

The 4 stepsof PSHA

The Cornell (1968) approach (1)


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seismic hazard 57

The Cornell (1968) approach (1)

P[E] = P E| S[ ]fs(s)ds

z = ii=1

N

iP(Z>z|m,r)fr= o

r=

mo

mu

(m) if (r)drdm

T= t/ln(1P(ZT >z))

El enfoque de Cornell (1968)

Application

El teorema de probabilidad total:

cada fuente GR distribution SZ geometry

If it is a Poisson process (stationary, independent, non-multiple events)

SF (s) = P[Sz[ ]=1 ezT

Promedio anual detasa deexcedencia

Tasa anual promedio

de ocurrencia

3RD GENERATION The Cornell (1968) approach (2)


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seismic hazard 58

SEISMOTECTONIC PROBABILISMThe Cornell (1968) approach (2)

Working hypotheses of the

Cornell (1968) approach

The eq magnitude is exponentiallydistributed

The eq number in time forms aPoisson process

The seismicity is spatially uniforminside the seismic sources (faults,areas, etc.)

(from Algermissen & Perkins, 1976)



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seismic hazard 59

SEISMOTECTONIC PROBABILISM( ) pp ( )

a b

c

d e

Contributing information

a = geology, historical & instrumentalseismicity

b = historical & instrumentalseismicityc = instrumental seismicity for PGA

historical seismicity for intensityd = statisticse = statistics




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seismic hazard 60

SEISMOTECTONIC PROBABILISM( ) pp ( )

The actual stepsin PSHA computation

A) Definition of SZsB) Seismicity characterisation

Attenuation relationC) Probability of ground motion

exceedenceD) Probability of ground motion

exceedence in T yrs

Uniformely distributed seismicityGutenberg-Richter law

Poisson distribution


SOURCE-TO-


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seismic hazard 61

SITEDISTANCE

Arcs of circles with centers at thesite approximate in Seisrisk IIIthe area of the quadrilater.

Examples of different earthquake source geometries: a) short fault that can bemodelled as a point source; b) shallow fault that can be modelled as a linearsource; c) 3D source zone modelled as an area source

(from Kramer, 1996)


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seismic hazard 62

FR(R)

Variations of source-to-site distance for different source zone geometries. Theshape of the PDF can be visualized by considering the relative portions of thesource zone that would fall between each of a series of circles (or spheres for3D problems) with equal differences in radius

(from Kramer, 1996)

fL( l)dl = fR(r)dr

fR(r) = fL (l)dl

dr

fL( l) = l /Lf

l2 = r2 rmin2

fR(r) = r

Lf r2 rmin

2

(b)

Many single sources, see (a)

FM(M)


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seismic hazard 63

( )GUTENBERG - RICHTER

LAW

log nm =a bmnm = 0e

m

nm = 0e(mm0)

with m0 = threshold

magnitude= b ln10

0 =10a

FM(m) =P[Mm0] =nm0 nm

nm0

=1 e(mm0)

fM(m) = d

dmFM(m) =e

(mm0)

Gutenberg-Richter recurrence law: a) meaning ofa

andb

parameters; b) application of Gutenberg-Richter law to worldwide seismicity data

FM(M)


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seismic hazard 64

M( )BOUNDED GUTENBERG -

RICHTER LAW

Bounded Gutenberg-Richter recurrencelaws for mo=4 and mmax=6, 7, and 8constrained by constant seismicity rate

where =exp(m0) is the rate ofoccurrence of earthquakesexceeding m0

nm = exp m m0( )[ ] exp mmax m0( )[ ]

1 exp mmax m0( )[ ]

FM(m) =P[M


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seismic hazard 65

CHARACTERISTICEARTHQUAKE

Youngs & Coppersmithdeveloped ageneralizedmagnitude-frequency

PDF that combined anexponential magnitudedistribution at lowermagnitudes with auniform distribution in

the vicinity of thecharacteristicearthquake.

Comparison of recurrence laws from bounded Gutenberg-Richter and characteristic earthquakemodels (from Youngs & Coppersmith, 1985).Inconsistency of mean annual rate of exceedance asdetermined from seismicity data and geologic data (from Schwartz and Coppersmith, 1984).

SEISMIC HAZARD PGA with 10% exceedanceprobability over various exposure


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seismic hazard 66

CURVE The individual components of the Eq are

complicated that the integrals cannot beevaluated analitically: numerical integration is

requiredP[E] = P E| S[ ]fS(s)ds

P[Z>z] = iP(Z>z| m,r)f

r= o

r=

mo

mu

(m) if (r)drdm

z = ii=1

NS

iP(Z>z| m,r)fr= o

r=

mo

mu

(m) if (r)drdm

z = ik=1

NR

j=1

NM

i=1

NS

P(Z>z| mj ,rk)fMi (m j )fR i (rk)mr

z = ik=1

NR

j=1

NM

i=1

NS

P(Z>z| m j ,rk)P[M=m j ]P[R =rk]

P ZT >z[ ]=1 ezT

Magnitude and distance ranges are divided into segments

Poisson model

times for 14 areas in NorthAmerica

Mean annual rateof exceedence

Hazard curve

Exceedence

probability

d f b d


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seismic hazard 67

0.001

0.01

0.1

1

0.1 1

ponti del Veneto

e

xceedence

probability

in

50

yrs

PGA

Spresiano

BotteonPeron

Fener

Hazard curves for 4 bridges in Veneto


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seismic hazard 68

MAXIMUM MAGNITUDE

The circles represent actualearthquake data. The dataset iscomplete for small magnitudes, butbecomes erratic for the larger. Atabout M=5, there are no records,

simply because the historical recordis usually too short. In some casespaleoseismology can fill some of thegap.


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seismic hazard 69

THE KIJKO APPROACH (1)

The maximum magnitude mmax is the upper limit of magnitudefor a given seismogenic source

The generic formula for estimation of mmax


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seismic hazard 70

THE KIJKO APPROACH (2)

Three cases are possible: eq magnitudes are distributed according to the G-R relation; eq magnitude distribution deviates largely from the G-R relation;

no specific model for the eq magnitude distribution is assumed.

THE KIJKOAPPROACH


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seismic hazard 71

APPROACH(3)

E1(z )=

e

z

d

E1(z ) = z 2 +2.334733z +0.250621

z z2 +3.330657z +1.681534( )

THE KIJKO


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seismic hazard 72

APPROACH (4)

THE KIJKO


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seismic hazard 73

APPROACH (3)

THE EARTHQUAKE CYCLE (1)


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seismic hazard 74


Some regions repeatedlyexperience earthquakes andthis suggests that perhaps

earthquakes are part of a cycle.The effects of repeatedearthquakes were first notedlate in the nineteenth centuryby American geologist G. K.Gilbert, who observed a fresh

fault scarp following the 1872Owens Valley, Californiaearthquake



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seismic hazard 75


For an ideal elastic-reboundfault, the stress on the faultperiodically cycles between a

minimum and maximum valueand if the two blocks continue tomove at a constant rate, therecurrence time (the timebetween earthquakes) is also

uniform



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seismic hazard 76


Unfortunately, actual faultsare more complex: the

recurrence time is notperiodic and we have fewobservations of completeearthquake cycles. In fact,the Nankaido region of Japanshows that neither the time

nor the slip is uniform fromearthquake-to-earthquake


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seismic hazard 77

THE GSHAP PROJECT(1)

The Gl obal Sei smi c Hazar d Assessment Pr ogram ( GSHAP) wasl aunched i n 1992 by t he I nt er nat i onal Li t hospher e Pr ogr am ( I LP)wi t h t he suppor t of t he I nt er nat i onal Counci l of Sci ent i f i cUni ons ( I CSU) , and endor sed as a demonst r at i on pr ogr am i n t hef r amewor k of t he Uni t ed Nat i ons I nt er nat i onal Decade f orNat ur al Di sast er Reduct i on ( UN/ I DNDR) . The pr i mar y goal ofGSHAP was t o cr eat e a gl obal sei smi c hazar d map i n a har moni zed

and r egi onal l y coor di nat ed f ashi on, based on advanced met hodsi n pr obabi l i st i c sei smi c hazard assessment s ( PSHA) . The GSHAPst r at egy was t o est abl i sh Regi onal Cent r es whi ch wer er esponsi bl e f or t he coor di nat i on and r eal i zat i on of t he f ourbasi c el ement s of modern PSHA:

1. Ear t hquake cat al ogue 2. Ear t hquake sour ce char act er i zat i on

3. St r ong sei smi c gr ound mot i on 4. Comput at i on of sei smi c hazar d.


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seismic hazard 78

THE GSHAP PROJECT (2) Seismic hazard map

produced by GSHAP(Giardini et al., 1999)http://www.seismo.ethz.ch/GSHAP/index.html


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seismic hazard 79

THE ESC PROJECT (1)

The ESC-SESAME is the firstever unified model forProbabilistic Seismic HazardAssessment for Europe andthe Mediterranean. It wasdeveloped within theframework of several recentprojects on global andregional seismic hazard

assessment and allows forhomogeneous hazardcomputation throughout thewhole European-Mediterranean domain.


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seismic hazard 80

THE ESC PROJECT(3)


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seismic hazard 81

(3)

Seismic hazard map of theEuropean Mediterraneanregion (Jimenez et al., 2003)http://wija.ija.csic.es/gt/earthquakes/

Predictive relationships of the expected ground motion (mainlyPGA) are nearly always obtained empirically by least-squaresregression on a particular set of strong motion parameter data


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seismic hazard 82

Schematic illustration of conditional probability of exceeding a particularvalue of a ground motion parameter for a given magnitude and distance

regression on a particular set of strong motion parameter data.Despite attempts to remove questionable data and the use ofquality-based weighting schemes, some amount of scatter in thedata is inevitable. The scatter results from randomness in the

mechanics of rupture and from variability and heterogeneity of thesource, travel path, and site conditions. Scatter in the data can bequantified by confidence limits or by the standard deviation of thepredicted parameter. Reflecting the form of most predictiverelationships, the standard deviation of the logarithm of thepredicted parameter is usually computed.

ATTENUATION

3rd Generation Seismotectonic ProbabilismTh C ll (1968) h


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seismic hazard 83

INGREDIENTS OF PSHA

Seismogenic zonation for source geometry

Earthquake catalogue for seismicity characterisation (rates, Mmax,recurrence)

Attenuation relations

The Cornell (1968) approach


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seismic hazard 84

General framework: Kinematic model of Adria

The SZs are drawnon the basis

of the slip vector patternrepresenting

the kinematic model

of the Adria microplate

Seismogenic zonation of Italy


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seismic hazard 85

Seismogenic zonation of Italy

Legend:1. Seismic source zones related to the interaction

between Adria and Europe.2. Alps/Apennine transfer zones.3. Seismic source zones related to the sinking

of the Adria lithosphereand to the uplift of the asthenosphere.

4. Seismic source zones related to the deactivationof the thrust belt - foredeep systemand to the counterclockwise rotation of Adria.

5. Seismic source zones of the Calabrian Arc.6. Seismic source zones inside the foreland region

and along the flexural margins.7. Seismic source zones in active volcanic regions.

Identification: supported by geology,neotectonics, seismicity

Geometry: contro lled by kinematics, seismici tyBehaviour: controlled by kinematics, neotectonics ,

intensity maps, fps

(from Slejko et al., 1999)

WHERE IS THE EPICENTER?


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seismic hazard 86

Image from: http://nisee.berkeley.edu/kozak/Images of Historical EarthquakesThe Jan T. Kozak CollectionFresco of 1361 in St. Mary chapel (Karlstein Castle, Prague)

illustrating the damage caused to the Arnoldstein castleby the Villach (Austria) earthquake of January 25, 1348

1348 Villach

1511 Idrija - Gemona

Doubts remain on the epicentersof the two strogest events in theEastern Alps

THE CONTRIBUTION OF THE


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seismic hazard 87

INSTRUMENTAL SEISMOLOGY

Fault plane solution

Fault

Hypocentral probability

Map of the historical earthquakes (1000 1980)


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seismic hazard 88

Seismogenic zone 10

MAP OF THE PRESENT-DAY SEISMICITY (SINCE 1977)


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seismic hazard 89

Principalfaults


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seismic hazard 90

Principal faultsin Friuli - Venezia Giulia

Tectonic scheme for PSHA

Seismogenic fault

Neotectonic fault

Seismicity characterisation of the SZs


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seismic hazard 91

Seismicity rates and maximum magnitude for SZ 4; different time periods are plotted (see legend);arrows indicate the rates suggested from the completeness analysis, large open squares the selected ones.The line is the Gutenberg-Richter interpolation, on which the maximum magnitude (Mmax) is evaluated.

Uncertain seismicity characterisation for some SZs


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seismic hazard 92

0.1

1

10

3.7 4 4.3 4.6 4.9 5.2 5.5 5.8 6.1 6.4 6.7 7 7.3 7.6 7.9

ZS 63 1936-1980

1915-1980

1895-1980

1843-1980

1787-1980 1626-1980

1501-1980

1300-1980

1000-1980

Scelta

Numeronormalizzato

(100anni)

Magnitudo

7.0008, 0.18595

0.1

1

10

3.7 4 4.3 4.6 4.9 5.2 5.5 5.8 6.1 6.4 6.7 7 7.3 7.6 7.9

ZS 10 1936-1980

1915-1980

1895-1980

1871-1980

1836-1980

1826-1980 1699-1980

1596-1980

1000-1980

Scelte

Numeronormalizzato

(100anni)

Magnitudo

0.1

1

10

3.7 4 4.3 4.6 4.9 5.2 5.5 5.8 6.1 6.4 6.7 7 7.3 7.6 7.9

ZS 54 1936-1980

1915-1980

1895-1980

1843-1980

1787-1980

1686-1980

1626-1980

1501-1980

1465-1980

Scelta

Nu

meronormalizzato

(100anni)

Magnitudo

0.1

1

10

3.7 4 4.3 4.6 4.9 5.2 5.5 5.8 6.1 6.4 6.7 7 7.3 7.6 7.9

ZS 67 1936-1980

1915-1980

1895-1980

1843-1980

1787-1980

1626-1980

1501-1980

1300-1980

1000-1980

Scelta

Nu

meronormalizzato

(100anni)

Magnitudo

I am fine I am poor

I am crazy

I am moody

INFLUENCE OF HI TORIC L ND IN TRUMENT L EI MICITY TO H Z RD


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seismic hazard 93

0.4

0.5

0.6

0.7

0.8

0.9

1

3.1 3.4 3.7 4 4.3 4.6 4.9 5.2 5.5 5.8 6.1

%PGA

Threshold magnitude

0.1

1

10

100

3.1 3.4 3.7 4 4.3 4.6 4.9 5.2 5.5 5.8 6.1 6.4

Number(in10

0yrs)

Magnitude

Seismicity rates Contribution to hazard

INFLUENCE OF HISTORICAL AND INSTRUMENTAL SEISMICITY TO HAZARD


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seismic hazard 95

PGA with a 475-yr return period

Computed considering

seismogenic zones


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seismic hazard 96

Accelerazione orizzontale di piccocon periodo di r itorno 475 anni

calcolata solo con le

faglie sismogenetiche


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seismic hazard 97

Accelerazione orizzontale di piccocon periodo di r itorno 475 anni

calcolata sia con lefaglie sismogeneticheche con quelleneotettoniche

Seismogenic zonation for the Eastern Alps


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seismic hazard 98

SZs, faults,historical and instrumental eqs

g p

Valutazione della pericolosita' sismicaalla scala nazionale


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seismic hazard 99

ZonazioneSismotettonica

RevisioneCatalogo dei

Terremoti

StimaProbabilistica

moto del suolo

GNDT 1990-1995

PGA

CATALOGO &DATABASE

SORGENTIAREALI

MCS

1996


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seismic hazard 100

Gruppo Nazionale per la Difesa dai Terremoti

Seismic Hazard Map of Italy

475-yr return period PGAon an average soil

In color boxes(red=rock, blue=stiff soil, green=soft soil):

year, place, magnitude, max recorded PGA,and number of deaths for recent eqs

Proposal for the seismic zonation 2003

Consensus seismic hazard maps:b i d t f th t ti l i i ti


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seismic hazard 101

basic products for the present national seismic zonation


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seismic hazard 102

The most recent

seismic hazardmap of Italy inagreement with

Ord. 3274

Comparison between results obtained with the Gumbel and Cornell approaches


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seismic hazard 103

8

8

0.22 g = 8 MCS

0.13 g = 7 MCS

8

8

The smoothed seismicity approach vs. the Cornell approach


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seismic hazard 104

Average PGA with T=475from the smoothed seismicity appr.

Average PGA with T=475from the Cornell appr.

Difference(smoothed seismicity - Cornell)


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seismic hazard 105

1 2

3

1 - Cornell approach with SZs2 - Cornell approach with faults3 - characteristic time-dependent eq on faults

From the 3rd to the 4th generation PSHASeismic Hazard in Central Italy

475-yr return period PGA


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seismic hazard 106

GROUND-MOTION PARAMETERS

SINGLE QUANTITIESPeak Ground Acceleration (PGA); Peak Ground Velocity (PGV): better than PGA because it is associated

with kinetic energy, which is proportional to the square of velocity.

COMBINED QUANTITIES (correlated with the damage onset; Benjamin et al., 1988) Arias Intensity; Cumulative Absolute Velocity.

SOME OTHER COMBINED QUANTITIES Effective Peak Acceleration (EPA); Housner Intensity (SI).

Which is better for seismic design and which for zonation?

Spectral Quantities


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seismic hazard 107SI is the area of the velocity spectrum

Response Spectrum

PGA

Quantification of seismic hazard


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seismic hazard 108

10

20

30

40

50

10

20

30

40

50

0.1 1

Pseudovelocity(cm/s)

Period (s)

b

0.06

0.08

0.1

0.3

0.5

0.7

0.06

0.08

0.1

0.3

0.5

0.7

0.1 1

Ab

soluteacceleration(g

)

Period (s)

a

Grumento

Gemona

Similar PGA

Different SA and PSV at 1 s

Grumento is the most hazardous site in Italy

100Spectru m intens ity 0.1 - 0.5 s

Different SIscan characterize sites

ith different seismicit


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seismic hazard 109

0.1

1

10

100

0.01 0.1 1 10

Spectru m in tensi ty 0.2 - 2.0 s

period (s)

M=7 D=10km

M=7 D=100km

M=4 D=10km

M=4 D=100km

0.1

1

10

00

0.01 0.1 1 10period (s)

M=7 D=10km

M=7 D=100km

M=4 D=10km

M=4 D=100km

with different seismicity

Similar SI

Different SI

Response spectra for the main Italian towns


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seismic hazard 110

Specific main soil

MILAN


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seismic hazard 111

0

0.2

0.4

0.6

0.8

0.1 1

MILANVENICETRIESTEFLORENCEROME

NAPLESMESSINACATANIA1st cat.2nd cat.3rd cat.

spectrala

cceleration(g)

period (s)

Uniform hazardresponse spectrum

for the mainItalian townsand design spectraof the seismic codepre-2003

10

T=1.0s

eleration(g)

10

T=0.2s

eration(g)


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seismic hazard 112

0.001

0.01

0.1

1

10

1 10 100

T=1.0s SD

Acceleration(g)

Distance (km)

Ms=7.0

Ms=5.5

Ms=4.0

d0.001

0.01

0.1

1

10

1 10 100

T=0.2s SD

Distance (km)

Ms=7.0

Ms=5.5

Ms=4.0

Acceleration(g)

c

0.001

0.01

0.1

1

1 10 100Distance (km)

Ms=7.0

Ms=5.5

Ms=4.0

Acce

b0.001

0.01

0.1

1

1 10 100Distance (km)

Ms=7.0

Ms=5.5

Ms=4.0

Accele

aSpectralAttenuation

Relationssolid = Ambraseys et al(1996)

dashed = Sabetta & Pugliese(1996)

IMAGES OF SEISMIC HAZARD (1)


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seismic hazard 113


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IMAGES OF SEISMIC HAZARD (3)


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seismic hazard 115


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seismic hazard 116

Comparison amongdifferent parameters

Every point is anItalian municipality

DEAGGREGATION


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seismic hazard 117

z(mj ,rk) P[M= mj ]P[R = rk] ii=1

NS

P(Z>z| mj ,rk)

It allows the estimate of the mostlikely earthquake magnitude anddistance: the mean annual rate ofexceedence is expressed as a

function of magnitude anddistance


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seismic hazard 118

SITE EFFECTS

Influence of: lithology morphology

SITE CLASSIFICATIONAND


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seismic hazard 119

AMPLIFICATION

FACTORS

SITE CLASSIFICATIONAND


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seismic hazard 120

ATTENUATION

RELATIONSAttenuation relations for European eqs (Ambraseys et al., 1996)

SOIL TYPES IN NE ITALY


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seismic hazard 121

HAZARD MAPS FOR NE ITALY


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seismic hazard 122

HAZARD MAPS FOR NE ITALY

Soft soil

rock

Stiff soil

SOIL HAZARD MAPS FOR NE ITALY


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seismic hazard 123

SOIL HAZARD MAPS FOR NE ITALY

PGA with a 475-yrreturn period

median values

with aleatory uncertainty

SOIL HAZARD MAP FOR FRIULI - VENEZIAGIULIA


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seismic hazard 124

GIULIA

HAZARD MAP OF FRIULI - VENEZIA GIULIAIN INTENSITY


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seismic hazard 125

IN INTENSITY

THIS IS THE END OF SEISMIC


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HAZARD

1.1. Ingenieria Sismologica

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Transcript of 1.1. Ingenieria Sismologica