7 eg- ce- earthquakes.ppsx

7/25/2019 7 EG- CE- EARTHQUAKEs.ppsx

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Dr. Abdelrahman Abueladas

Lecture 7

Faculty of EngineeringCivil Engineering

Engineering Geology

CE

Dr. Abdelrahman Abueladas Civil Engineering Class Engineering Geology Lecture 7

Earthquake


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Turkey, 1999

Earthquake

arthquake

2Dr. Abdelrahman AbueladasCivil Engineering Class


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What is an Earthquake? An earthquake is the vibration, sometimes violent, o the

Earth!s sur ace that ollo"s a release o energy in the Earth!scrust.

Caused by volcanic activity, meteorite im#acts, undersealandslides , e$#losions o nuclear bombs or most commonly, bymovement o the Earth across a ault

Fault % racture in the Earth across "hich the t"o sides moverelative to each other

Stresses build u# until enough to cause roc&s to racture andshi t, sending o "aves o

seismic energy, elt as earth'ua&e

(


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Faults are com#le$ )ones o brea&age "ith irregularsur aces, many miles "ide and long

*tress builds u# until rupture occurs at "ea& #oint

and #ro#agatesalong ault sur ace

+oint "here ru#ture

irst occurs ishypocenter or ocus +oint directly above

hy#ocenter on sur aceis epicenter

-


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*eismic "aves radiate rom the focus #oint o theinitial movement or sli# on the ault. /he epicenter is the geogra#hic #oint on the earth!s sur ace above

the ocus.

Earthquake the sha&ing or vibration o the groundoccurs "hen roc& suddenly brea&s along a ault



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Types of Seismic waves1 !o"y waves#

$rimary waves %$ 1 /he astest traveling "aves.2 Com#ressional "ave travel.

( +article motion is #arallel to the#ro#agation direction o the"ave ront.

Secon"ary Waves %S *hear "aves.2 *lo"er than + "aves.( +article motion is #er#endicular to the

#ro#agation direction o the"ave ront.

- * "aves do not travel in luids.

' Surface waves#+ro#agate near the earth sur ace.



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Compressional Wave (P-Wave) Animation

1 !o"y waves#(& $rimary waves %$ 1 /he astest traveling "aves.2 Com#ressional "ave travel.

( +article motion is #arallel to the #ro#agation direction o the"ave ront.Dr. Abdelrahman Abueladas Civil Engineering Class Engineering Geology Lecture 7

7


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Shear Wave (S-Wave) Animation

((& Secon"ary Waves %S *hear "aves.2 *lo"er than + "aves.( +article motion is #er#endicular to the #ro#agation directiono the "ave ront.

- * "aves do not travel in luids.Dr. Abdelrahman Abueladas Civil Engineering Class Engineering Geology Lecture 7

3


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a) Rayleigh Wave (R-Wave) Animation

' Surface waves#+ro#agate near the earth sur ace



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b) Love Wave (L-Wave) Animation

+article motion is hori)ontal and #er#endicular to the direction o#ro#agation 5transverse .

Am#litude decreases "ith de#th. 6aterial returns to its original sha#e a ter "ave #asses.



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Focus

Mantle

SeismographCore S P

S u r f a c e w a v e s



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Focus

Mantle

SeismographCore S P

S u r f a c e w a v e s

Seismic waves travel through Earth and over itssurface.



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)evelopment of Seismology *eismology% study o earth'ua&es Earliest earth'ua&e device% China, 1(2 8.C. 9nstruments to detect earth'ua&e "aves% seismometers 9nstruments to record earth'ua&e "aves% seismographs Ca#ture movement o Earth in three com#onents% north

south* east west an" vertical

:ne #art stays as stationary as#ossible "hile Earth vibrates%heavy mass i$ed by inertia in

rame that moves "ith the Earth,and di erences bet"een#osition o the rame and themass are recorded digitally

Dr. Abdelrahman Abueladas Civil Engineering Class Engineering Geology Lecture 71(


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Waves# +mplitu"e % dis#lacement Wavelength % distance bet"een successive

"aves

$erio" % time bet"een "aves 5; 1< re'uency Frequency % number o "aves in one second

5her), =)

)evelopment of Seismology

Dr. Abdelrahman Abueladas Civil Engineering Class Engineering Geology Lecture 71-


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Spring

Mass

Seismograph



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Spring

Mass

The mass is looselycoupled to Earth.



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Recordingpen

Earthmoves up



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Recordingpen

Earthmoves up

Upward movement of the Earth causesdownward relative movement of the mass andvice versa.



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Earth

moves down



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Earthmoves down

The pen traces thedifferences in motion.



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Earthmoves left

Earthmoves right

Earthmoves sideto side

Mass

!inge



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Minutes

Surface waves

"

P S

#" $" %" &" '"

Seismogram



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Minutes

Surface waves

The waves travel at different speeds and arrive atthe seismograph at different times.

"

P S

#" $" %" &" '"



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Seismograph

FocusSeismograph

Seismograph

Epicenter

Dr. Abdelrahman Abueladas Civil Engineering Class Engineering Geology Lecture 72-


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Seismograph

FocusSeismograph

Seismograph

Epicenter

Seismic waves arrive at distantseismographic stations at differenttimes.



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(istance traveled from earth)ua*e epicenter +*m,

T i m e e

l a p s e

d a

f t e r s t a r t o

f e a r t

h ) u a

* e

+ m i n ,

%-minuteinterval at#'"" *m

$""" &""" """ /""" #" """

$'

$"

Seismogram0

##-minuteinterval at/ "" *m/-minute

interval at' "" *m

#'

#"

'

"

Seismogram1

SeismogramC

S wave

P wave



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T i m e e

l a p s e

d a

f t e r s t a r t o

f e a r t

h ) u a

* e

+ m i n ,


$""" &""" """ /""" #" """

$'

$"

Seismogram0


interval at' "" *m

#'

#"

'

"

Seismogram1

SeismogramC

S wave

P wave

1ecause P waves travel faster than S waves theinterval 2etween their travel-time curves

increases with distance.



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T i m e e

l a p s e

d a

f t e r s t a r t o

f e a r t

h ) u a

* e

+ m i n ,


$""" &""" """ /""" #" """

$'

$"

Seismogram0


interval at' "" *m

#'

#"

'

"

Seismogram1

SeismogramC

S wave

P wave

1ecause P waves travelfaster than S waves theinterval 2etween theirtravel-time curves

increases with distance.

1y matching the o2servedinterval to the curves wecan determine the distancefrom the station to the

epicenter.



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#'"" *m#'"" *m0011

' "" *m' "" *m

/ "" *m/ "" *m

CC

3f we then draws a circle around eachseismographic station 4


3f we then draws a circle around each


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#'"" *m#'"" *m0011

EpicenterEpicenter

' "" *m' "" *m

/ "" *m/ "" *m

CC

3f we then draws a circle around eachseismographic station 4

the point at which the circles intersect is the earth)ua*e5s

epicenter .Dr. Abdelrahman Abueladas Civil Engineering Class Engineering Geology Lecture 7(


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0mplitude6$% mm

Richtermagnitude

0mplitude+mm,

3 n t e r v a

l 2 e

t w e e n

S a n

d P w a v e s

+ s ,

( i s t a n c e

+ * m

,

P S

S-wave interval 6 $& secondsP-wave

Dr. Abdelrahman Abueladas Civil Engineering Class Engineering Geology Lecture 7(1


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0mplitude6$% mm

Richtermagnitude

0mplitude+mm,

3 n t e r v a

l 2 e

t w e e n

S a n

d P w a v e s

+ s ,

( i s t a n c e

+ * m

,

P S


0 seismologistmeasures theamplitude ofthe largest

seismicwave4



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0mplitude6$% mm

Richtermagnitude

0mplitude+mm,

3 n t e r v a

l 2 e

t w e e n

S a n

d P w a v e s

+ s ,

( i s t a n c e

+ * m

,

P S


0 seismologistmeasures theamplitude of thelargest seismic

wave4

4and the timeinterval 2etween

the P- and S-wavesto determine thedistance from theepicenter.

Dr. Abdelrahman Abueladas Civil Engineering Class Engineering Geology Lecture 7((


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0mplitude6$% mm

Richtermagnitude

0mplitude+mm,

3 n t e r v a

l 2 e

t w e e n

S a n

d P w a v e s

+ s ,

( i s t a n c e

+ * m

,

P S


0 seismologistmeasures theamplitude of thelargest seismic

wave4

4and the timeinterval 2etween

the P- and S-wavesto determine thedistance from theepicenter.

1y connecting thepoints the seismologist determines theRichter magnitude.

Dr. Abdelrahman Abueladas Civil Engineering Class Engineering Geology Lecture 7(-


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,agnitu"e >is actually a measurement o theground dis#lacement 5or #article dis#lacementobtained rom a seismogram. /he grounddis#lacement is the same as the am#litude o theseismic "ave and hence the larger the "avemotion, the greater the magnitude.?

-ichter magnitu"e >/he magnitude o any shoc&is ta&en as the logarithm o the ma$imum traceam#litude, e$#ressed in microns, "ith "hich thestandard short-period torsion seismometer "ouldregister that shoc& at an e#icentral distance o1 &m>



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Intensity scale -- a scale forestimate earthquake shaking

based on the destructiveeffects and damage.

Mercalli scale . Invented by

Giuseppe Mercalli in 190 !this scale uses theobservations of the people"ho e#perienced the

earthquake to estimate itsintensity.

Giuseppe Mercalli (FromWalker, 1982)



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ARTHQUAK INT NSITY vs. MAGNITUD

Earth'ua&e intensity measures the e ect on #eo#le and buildings@sed to assess historical and archaeological records



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Seismographicstations

Fault



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First motion +pulltoward epicenter,


-Dr. Abdelrahman AbueladasCivil Engineering Class


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First motion+push awayfrom epicenter,

First motion+push awayfrom epicenter,

Dr. Abdelrahman Abueladas Civil Engineering Class Engineering Geology Lecture 7-1


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Dr. Abdelrahman Abueladas Civil Engineering Class Engineering Geology Lecture 7-2


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Tsunami generation

Thrust fault

S h a l l o w

w a t e r

Tsunami formation/sunami is a a#anese "ord "ith the English translation,>harbor "ave.>

Dr. Abdelrahman Abueladas Civil Engineering Class Engineering Geology Lecture 7-(


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Tsunami generation

Thrust fault

S h a l l o w

w a t e r

0n earth)ua*e producesa surge of water that movesoutward as a tsunami.

0 tsunami is only a fewcentimeters high in the deepocean 2ut can increase tomany meters high close toshore.


--

Tsunami pr !u"e! #$


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Tsunami pr !u e! #$earthquake !isp%a"ement &

"ean &% r.

(mportant points#(n "eep ocean* tsunami has small amplitu"e an"travels with spee" of .et airliner/When approaching lan"* spee" slows an" amplitu"eincreases "ramatically/


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Tsunami wave propagation characteristics note that as water depth becomes shallower, waves slow down, become shorter wavelength,

and have larger amplitude

NOAA


-

Computer simulation of tsunami radiation


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Computer simulation of tsunami radiation.

!awaii

& hr &$ min

7orth

0merica

7orth

0mericaEpicenter

Main tsunami "ave reaches $a"aiian Islands about %.& hours after theearthquake.

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#a% Seismi" Ha'ar! Assessment (r )ram *GSHA(+


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-3http://www.seismo.ethz.ch/gshap/

/he Global *eismic =a)ard Assessment +rogram 5G*=A+ "as launched in 1442 by the 9nternationalLithos#here +rogram 59L+ "ith the su##ort o the 9nternational Council o *cienti ic @nions 59C*@ , andendorsed as a demonstration #rogram in the rame"or& o the @nited Bations 9nternational Decade orBatural Disaster eduction 5@B


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Liquefaction is defined as 'the transformation of a granularmaterial from a solid state into a liquefied state as aconsequence of increased pore-"ater pressure'

Figure 1 - (ketch of a packet of "ater-saturated sand grains illustrating the process ofliquefaction. (hear deformations )indicated by large arro"s* induced by earthquakeshaking distort the granular structure causing loosely packed groups to collapse asindicated by the curved arro" (Youd, 1992).


Liquefaction

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Liquefaction


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Li'ue action is one o the most im#ortant and com#le$to#ics in geotechnical earth'ua&e engineering.

Li'ue action occurs "hen saturated soils lose theirstrength and a##ear to lo" as luids "hen sha&en byearth'ua&e "aves 5 Seed and Idriss, 1982; Kramer,

1996 ./he strength o the soil shrin&s to the #oint "here it isunable to hold structures or remain stable.

/he damage caused by li'ue action include slo#eailures, bridge and building oundation ailures, andlotation o buried structures.

Liquefaction

0

+here are several factors that may affect the liquefaction


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here are several factors that may affect the liquefactionsusceptibility of soil deposits such as,

1- epth and thickness of the strata.

- elative density! grain si/e.- ge of sediments.%- 2resence of overlying non-liquefiable layers.&- +he previous seismic history (Seed, 1979; Seed and driss, 1982; !"ermeier and #ond,1999).

+here are three conditions must e#ist for liquefaction tooccur,

)1* (oil susceptible to liquefaction.) * (hallo" ground"ater table.) * (trong ground shaking.

01

/he ty#es o sediments most susce#tible to


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yli'ue action are saturated silt and san" de#osits. 9 the silt and sand sediments are overlain by a

nonli'ue iable stratum such as clay, the li'ue actionsusce#tibility "ill be very high.6ost commonly, li'ue action initiates at de#thsbet"een ' and 0 m belo" the ground sur ace, but itcan also initiate at de#ths u# to 2 m or even more (Seedand Idriss, 1982) .

Li'ue action usually occurs at the same location

"hen the soil and ground "ater conditions haveremained unchanged.

/he li'ue action distance is #ro#ortional "ith theearth'ua&e magnitude.

02

,etho"s of the +nalyses


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, y

*everal ield tests are usually used or the evaluation oli'ue action resistance o sandy soils, including%1 /he standard #enetration test 5*+/ .2 /he cone #enetration test 5C+/ .( /he 8ec&er #enetration test 58+/ .- *hear "ave velocity measurement 5 s .

0(

/he #oint based susce#tibilityusing combined scheme based on


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using combined scheme based ona##lying a +GA o .(g integratedin the study area.5Abueladas, 2 1-

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Relation bet een Risk and Hazard


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3arthquake scientists and engineers make an important conceptualdistinction bet"een ha/ard and risk.

Hazard is the property of an earthquake that causes loss of life ordamage

Risk is the probability of loss of life! in4ury! or damage

Relation bet een Risk and Hazard

Risk ! Hazard " #ulnerability " $"posure $a/ard is the frequency of a level of shaking )liquefaction!

landslide! fault rupture* 5ulnerability measures the likelihood that something like a

building "ill be damaged 3#posure is the number of people! buildings! structures that are

e#posed to the ha/ard. +his is called an inventory. %eologists and seismologists define t&e eart&quake &azard $ngineers 'builders( masons( etc.) reduce t&e risk by decreasing t&e

*ulnerability of structures to ground motion 00

7 eg- ce- earthquakes.ppsx

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