Topic 02 Ground Motions Jrm Oct06

7/29/2019 Topic 02 Ground Motions Jrm Oct06

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Earthquake Effects 1

Earthquakes: Cause and Effect


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Fundamentals of Earthquake Engineering

Earthquakes: Cause and Effect

Why Earthquakes Occur

How Earthquakes are MeasuredEarthquake EffectsMitigation Strategy

Earthquake Time Histories

Revised 2/8/05


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Seismic Activity >M5 Since 1980

Ring of Fire

Mid-Atlantic Ridge

Alpide Belt

Alpide Belt


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Crustal Plate Boundaries

Plate Boundaries


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Plate Tectonics: Driving Mechanism


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Continental-Continental collision

(orogeny)


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Oceanic-Continental Collision

(subduction)


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San Andreas Fault System


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Seismicity of North America

1811 New Madrid

M > 8.01886 Charleston

M > 7.0

Pacific

Plate

North American

Plate


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Faults and Fault Rupture

Fault plane

Hypocenter

(focus)

Epicenter

Rupture surface


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Types of Faults

Strike Slip(Left Lateral)

Strike Slip(Right Lateral)

Normal Reverse (Thrust)


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New Fence

Time = 0 Years

Elastic Rebound Theory


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Old Fence

New Road

Time = 40 Years


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Old Fence

Time = 41 Years

New Road


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San Andreas Fault Offset - 1906 S.F. EQ M8.2

fault trace

2.6-m fence offset

from fault

Photo credit: USGS.


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Seismic Wave Forms

(Body Waves)

Compression Wave(P Wave)

Directiono

f

Propagation

Shear Wave

(S Wave)

Directionof

Propagatio

n


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Love Wave Rayleigh Wave

Seismic Wave Forms

(Surface Waves)

Directionof

Propagation

Directionof

Propagation


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Love WavesP Waves S Waves

Arrival of Seismic Waves


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Effects of Seismic Waves

Fault Rupture

Ground ShakingLandslides

LiquefactionTsunamis

Seiches

Surface Fault Rupture;


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Surface Fault Rupture;1999 Chi Chi Taiwan Earthquake (M7.7)


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If a saturated sand is subjected to groundvibrations, it tends to compact and decrease in volume.

If drainage is unable to occur, the tendency todecrease in volume results in an increase inpore pressure.

If the pore water pressure builds up to the point atwhich it is equal to the overburden pressure, the

effective stress becomes zero, the sand loses itsstrength completely, and liquefaction occurs.

Liquefaction

Seed and Idriss

Liquefaction Field of Sand Boils


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Liquefaction - Field of Sand Boils

Liquefaction damage - Niigata Japan


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Liquefaction damage - Niigata, Japan

1964

L l S di


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SandBoils

UnliquefiedSoil

LiquefiedSoil

mostly horizontal deformation of gently-sloping

ground (< 5%) resulting from soil liquefaction

one of most pervasive forms of ground damage;

especially troublesome for lifelines

Lateral Spreading

Liquefaction and Lateral Spreading


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Liquefaction and Lateral SpreadingNishinomiya Harbor Bridge - 1995 Kobe, Japan EQ

Liquefaction and Lateral Spreading


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Liquefaction and Lateral SpreadingNishinomiya Harbor Bridge - 1995 Kobe, Japan EQ

Lateral Spreading


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Lateral Spreading1999 Chi Chi EQ M7.7 (Taiwan)

Landslide on Coastal Bluff


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Landslide on Coastal Bluff

Loma Prieta Earthquake, California, 1989

Tsunami Damage: Seward Alaska, 1964


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Banda Aceh, Indonesia


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Cause of Tsunamis

Tsunamis are created by a suddenvertical movement of the sea floor.

These movements usually occur in

subduction zones.

Tsunamis move at great speeds, often 600

to 800 km/hr.

Cause of Tsunamis


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Cause of Tsunamis

Cause of Tsunamis


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Cause of Tsunamis


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Result of Ground Shaking;


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g;

1994 Northridge, California Earthquake


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Earthquake effect Strategy

Fault rupture AvoidTsunami/seiche Avoid

Landslide AvoidLiquefaction Avoid/resistGround shaking Resist

Mitigation Strategies

Measuring Earthquakes


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Measuring Earthquakes

INTENSITY

Subjective measure of human reaction and damage

Used where instruments are not availableVery useful in historical seismicity

MAGNITUDEMeasured with seismometersDirect measure of energy releasedPossible confusion due to different measures


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Modified Mercalli Intensity

Not felt except by a few under especiallyfavorable circumstances

Felt only by a few persons at rest, especially on

upper floors of buildings. Suspended objects may swing.

Felt quite noticeably indoors, especially onupper floors of buildings. Standing automobiles mayrock slightly. Vibration like passing truck.

I.

II.

III.



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During the day felt indoors by many, outdoors byfew. At night, some awakened. Dishes, windows,doors disturbed; walls make creaking sound. Sensation

like heavy truck striking building. Standing automobilesrocked noticeably. [0.015 to 0.02g]

Felt by nearly everyone, many awakened. Some

dishes and windows broken. Cracked plaster.Unstable objects overturned. Disturbance of trees, polesand other tall objects. [0.03 to 0.04g]

Felt by all. Many frightened and run outdoors.Some heavy furniture moved. Fallen plaster and

damaged chimneys. Damage slight. [0.06 to 0.07g]

IV.

V.

VI.



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Everybody runs outdoors. Damage negligible inbuildings of good design and construction, slight tomoderate in well built ordinary structures, considerable

to poorly built or badly designed structures. Noticedby persons driving cars. [0.10 to 0. 15g]

Damage slight in specially designed structures,considerable in ordinary construction, great inpoorly built structures. Fall of chimneys, stacks,

monuments. Sand and mud ejected in smallamounts. Changes in well water. Persons drivingcars disturbed. [0.25 to 0.30g]

VII.

VIII.



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Damage considerable in specially designedstructures, well designed frame structures thrownout of plumb, damage great in substantial buildings

with partial collapse. Buildings shifted off foundations.Ground cracked conspicuously. Underground pipesbroken. [0.50 to 0.55g]

Some well built wooden structures destroyed. Mostmasonry and frame structures destroyed withfoundations badly cracked. Rails bent. Landslides

considerable from river banks and steep slopes.Shifted sand and mud. Water splashed over banks.[More than 0.60g]

IX.

X.



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Few, if any (masonry) structures left standing.Bridges destroyed. Broad fissures in ground.

Underground pipelines completely out of service.Earth slumps and land slips in soft ground.Rails bent greatly.

Damage total. Waves seen on ground surface. Linesof sight and level distorted. Objects thrown into air.

XI.

XII.

Isoseismal Map for the Giles County, Virginia

E th k f M 31 1897


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Earthquake of May 31, 1897.


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Isoseismal Map

from New Madrid

Earthquake

Dec. 16, 1811

1886 Charleston EQ Felt OverE t US!


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Eastern US!

New York >600 mi.

Charleston

St. Louis > 650 mi.

Chicago > 700 mi.

1980 M5 2 Sharpsburg KY EQ


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1980 M5.2 Sharpsburg KY EQ

Sharpsburg KY, EQdamage was $20 million

Why not New Madrid Eqsin KY? (same Iapetan-agefaults present here)

Note pattern relative toOH River

Isoseismal Map for February 9, 1971

San Fernando CA Earthquake


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San Fernando CA Earthquake

Comparison of Isosiesmal Intensity for Four Earthquakes


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Instrumental Seismicity


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Instrumental Seismicity

ML = Log [Maximum Wave Amplitude (in mm/1000)]

Recorded Wood-Anderson Seismograph

100 km from Epicenter

Magnitude (Richter, 1935)

Richter Magnitude Also called Local Magnitude

M it d (i l)


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M = Log A +f(d,h) +CS + CR

A=Wave Amplitude of seismometer needle

F(d,h) accounts for focal distance and depth

CS, CR, are Station and Regional Corrections

Magnitude (in general)

Other Wave Based Magnitudes


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MS Surface-Wave Magnitude (Rayleigh Waves)

mb Body-Wave Magnitude (P Waves)

MB Body-Wave Magnitude (P and other Waves)

mbLg (Higher Order Love and Rayleigh Waves)

MJMA (J apanese, Long Period)

Other Wave Based Magnitudes

Moment Magnitude


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g

Seismic Moment= MO =AD

=Modulus of RigidityA=Fault Rupture Area

D=Fault Dislocation or Slip

Moment Magnitude =MW = (Log MO-16.05)/1.5

[Units=Force times Distance]

Moment Magnitude vs. Other Magnitude Scales(Magnitude Saturation)


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( g )

Approximate RelationshipBetween Magnitude and Intensity


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0

1

2

3

4

5

6

7

8

9

10

1 2 3 4 5 6 7 8 9 10 11 12

Intensity

Magnitude

Richter (Local)

MbLg

Between Magnitude and Intensity

167.0 0 += IM L

66.149.0 0 += ImbLg

Seismic Energy Release

L E 15M +118


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Log E = 1.5 MS+ 11.8

1E+12

1E+14

1E+16

1E+18

1E+20

1E+22

1E+24

1E+26

1E+28

0 2 4 6 8 10

Magnitude, Ms

Ene

rgy,

Ergs

..

311000

Seismic Energy Release


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1E+12

1E+14

1E+16

1E+18

1E+20

1E+22

1E+24

1E+26

1E+28

0 2 4 6 8 10

Magnitude, Ms

E

nergy,

Ergs

..

Nuclear Bomb

1964 Alaska Earthquake

1906 San Francisco Earthquake

1972 San Fernando Earthquake

Atomic Bomb

1978 Santa Barbara EQ

Ground Motion Accelerograms


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Sources: NONLIN (more than 100 records)

Internet (e.g. National Strong Motion Data Center) USGS CD ROM

Uses: Evaluation of Earthquake Characteristics Development of Response Spectra

Response History Analysis

Sample Ground Motion records


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Ground Motion Characteristics


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Ground Motion Characteristics

Acceleration, Velocity, Displacement

Effective Peak Acceleration & Velocity

Fourier Amplitude Spectra

Duration (Bracketed Duration)

Incremental Velocity (Killer Pulse)

Response Spectra

Other (See Naiemand Anderson)

400

600

Horizontal Acceleration (E-W), cm/sec2

Typical Earthquake Accelerogram Set


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-600

-400

-200

0

200

0 5 10 15 20 25 30 35 40 45

-600

-400

-200

0

200

400

600

0 5 10 15 20 25 30 35 40 45

-600

-400

-200

0200

400

600

0 5 10 15 20 25 30 35 40 45

Tim e (s ec)

Vertical Acceleration, cm/sec2

Horizontal Acceleration (N-S), cm/sec2

Time, Seconds Loma Prieta Earthquake

-463 cm/sec2

-500 cm/sec2

-391 cm/sec2

Definition of Bracketed Duration


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-600

-400

-200

0

200

400

600

0 5 10 15 20 25 30 35 40 45

Bracketed Duration

0.05g

Time, Seconds

Acceleration, cm/sec2

Definition of Incremental Velocity

600



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Time, Seconds

-400

-300

-200

-100

0

100

200

300

400

8 9 10 11 12

-600

-400

-200

0

200

400

600

0 5 10 15 20 25 30 35 40 45


Time, Seconds

Concept of Fourier Amplitude Spectra

)2()2i ()2()(2/2/ 2/ NN N

jfAjfbjf


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-600

-400

-200

0

200

400

600

0 5 10 15 20 25 30 35 40 45


N points at timestep dt

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30

Frequency (Hz)

N/2points at frequencydf


)2cos()2sin()2cos()(1

001 1

000 jj

j

j j

jjg jfAajfbjfaatv

== =++=++

22jjj baA +=Ndtdff /10 ==

=

j

j

ja

barctan

Ground Motion Frequency Content (1)

1.2

HORIZONTAL Acceleration (E W) cm/sec2


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-600

-400

-200

0

200

400600

0 10 20 30 40 50

-600

-400

-200

0

200

400

600

0 10 20 30 40 50

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 5 10 15 20 25 30

Frequency(Hz)

F

ourierAmplitude

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 5 10 15 20 25 30

Frequency (Hz)

Fou

rierAm

plitude

HORIZONTAL Acceleration (E-W), cm/sec2

VERTICAL Acceleration, cm/sec2

Time, Seconds

Development of an Elastic Displacement

Response Spectrum


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-0.40

-0.20

0.00

0.20

0.40

0.00 1.00 2.00 3.00 4.00 5.00 6.00

TIME, SECONDS

GROUND

ACC

,g

T=2.0 Seconds

T=0.6 Seconds

El Centro Earthquake Record

Maximum Displacement Response Spectrum

-4.00

-2.00

0.00

2.00

4.00

0.00 1.00 2.00 3.00 4.00 5.00 6.00DISPLACEMEN

T,

in.

-8.00

-4.00

0.00

4.00

8.00

0.00 1.00 2.00 3.00 4.00 5.00 6.00DISPLACEMENT

,In.

0

2

4

6

8

10

12

14

16

0 2 4 6 8 10

PERIOD, Seconds

DISPL

ACEMENT,

inches

Topic 02 Ground Motions Jrm Oct06

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