Introduction to
ENGINEERING
SEISMOLOGY
Gregory MacRae
Many slides from Durgesh C. Rai
Department of Civil Engineering,
Indian Institute of Technology Kanpur, Kanpur 208016
Rai
BACKGROUND
4 Loss ($$$)
• Damage
• Death
• Downtime
3 Response
Site Surface
Rock
Fault
2b
R
2a Ground Motions
Magnitude M
2
1 Faulting
MacRae, 2009
BACKGROUND
4. Loss Related Decisions
- People
- Government
- Business
- Planners
3 Controlling
Response
- Engineers
(Planning, Preparation, Response, Recovery)
Site Surface
Rock
Fault
2b
R
2a Ground Motions
- Seismologists
Magnitude M
3
1 Rupture
- Geologists
MacRae, 2009
BACKGROUND
4. Loss Related Decisions
POLICY
- People
ENGINEERING
- Government
- Business
- Planners
3 Controlling
Response
- Engineers
(Planning, Preparation, Response, Recovery)
Site Surface
Rock
Fault
2b
R
2a Ground Motions
- Seismologists
Magnitude M
4
1 Rupture
- Geologists
SCIENCE
MacRae, 2009
Defining an
Earthquake…
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Mythology
The Myths…
derrickdent.blogspot.com
hikataewa.co.nz
“The Earth is held up by 4 elephants that stand on the back of a turtle.
The turtle is balanced in turn on a cobra. When any of these animals
moves, the Earth will tremble and shake.” - India
6
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Science
An earthquake is a sudden, rapid shaking of the Earth
caused by the release of strain energy stored in rocks.
7
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Why and where
Earthquakes occur…
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The Inside Story
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Layers of the Earth
Layered (like hard-boiled egg)
Crust is like the shell
~ 65 km on continents
~ 10 km on ocean floors
Mantle is like the white
Plastic, semi-solid consistency
Continues to 2,900 km depth
Crust
Mantle
Outer
Core
Inner
Core
Core is like the yolk
Liquid outer core:
Continues to 5,100 km depth
Solid metallic core:
Fe & Ni
Continues to the Earth’s center
10
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Local Convective Currents
In the Mantle
~260 km of semi-molten
mantle rises due to heat
Sinks when temperature drops
Similar to movement you observe
when you boil water in a clear
glass pot
Crust is fractured
Convective movement acts as
drag force on crustal plates
: Causes separation
where mantle is rising
: Causes collision
where mantle is sinking
11
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The Circulations…
Since 4 billion years
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PANGEA theory…
The Super-continent
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The Rift…
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Continental Drift Theory
Crust broke about 4 billion years ago
Since then…
Plates are in slow,
but constant motion
(~2-15 cm/year)
Rate is similar to growth of
fingernails!
But, this is fast enough for rocks
The theory says that they traveled
around the Earth 11 times in last 4
billion years!
15
Continents 200 million years ago
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Some years later…
Continental Drift…
Today
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Continental Drift…
6400 km journey
>2900 km wide collision
2000 km shortening
~300 km compression in the
making of Himalayas itself
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Tectonic Activity…
Tethys
Ocean
19
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Tectonic Activity…
Tethys
Ocean …
reduced
20
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Tectonic Activity…
Tethys
Ocean …
removed
21
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Tectonic Activity…
22
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Remains of
the Tethys Sea
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Tectonic Activity…
• Today…
24
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The Rings of Fire…
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Spreading of Ocean Basins…
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The
Ocean
Ridge
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Subduction
of
Ocean
Basins…
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Earth Processes at Work
29
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Global Seismicity
30
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The Plates…
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Seismic Setting
Eurasian Plate
North American Plate
Pacific
Plate
IndoAustralian
Plate
African
Plate
South
American
Plate
Antarctic Plate
32
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33
The TSUNAMIS…
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How
Earthquakes occur…
Eurasian Plate
 The
mighty
Himalaya
stretching east to west over
2900 km of length is a result
Indian
Plate
of continental
convergence
and collision between Indian
Arabian
Sea and Eurasian plates.
One of the most
seismically
active regions
of the world
 It is one of the most
seismically
active
intercontinental regions of the
world.
Indian Ocean
Bay of
Bengal
What is an Earthquake?…
• Brittle Material
Force F
Maximum
Force
F
Rupture
F
Final elongation
is small
0
Elongation of Bar
36
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Elastic Rebound Theory…
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Elastic Rebound theory
• Elastic Strain Build-Up and Brittle Rupture
Stage A
Stage B
Slip
38
Stage C
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Elastic Rebound Theory…
EQ
Elastic Stress
Cumulative Slip
EQ
39
EQ
C
Slip
B
A
A
C
Time (years)
Strength
Energy
Build-Up
A
B
C
Energy
Release
Time (years)
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Elastic
Rebound
Theory…
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The Slip…
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Orange Grove…
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Historic Seismicity of Valparaiso
43
Bolt (1993)
Multiple fractures…
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The horizontal slip…
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The
vertical
slip…
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Types of Inter-Plate Boundaries
Convergent Boundary
Transform Boundary
47
Divergent Boundary
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The ACTUAL Slip…
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Types of Faulting
Dip Slip Faults
49
Strike Slip Faults
Thrust
(Reverse)
Left
Normal
Right
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Reservoir-Triggered
Earthquakes…
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Indian-Subcontinent
Earthquake scenario…
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Seismological Map
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Seismic Hazard map
53
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Seismic Hazard map
54
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Geographical Layout &
Tectonic Plate Boundaries
Eurasian Plate
Himalayas
Gangetic
Plains
Narmada
Plains
Mahanadi
Plains
Deccan Shield
Godavari
Plains
Arabian Sea
Indo-Australian
Plate
Bay of Bengal
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Some Past Earthquakes
2005 Kashmir
1935 Quetta
1905 Kangra
1897 Assam
1950 Assam
2011 Sikkim
2001 Bhuj
1934 Bihar-Nepal
Magnitude
2004 Sumatra
56
<5
5<6
6<7
7<8
>8
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Indian Seismic Zone Map
57
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Basic Terminology in
Earthquake Engineering
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Elastic Rebound Theory
Stress Build-up
Sudden Release
Slip
Fault Line
Fault Line
59
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Focus (Hypocenter)
• Point where motion first starts
Area/volume
ruptured
Focus
60
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Epicenter
• Projection of focus on ground
90
61
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Focal Depth
• Depth of focus below ground
< 70 km
Shallow Focus EQs
70 to 300 km
Intermediate Focus EQs
> 300 km
Deep Focus EQs

Epicenter
90
Focus
62
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Epicentral Distance
• Distance of epicenter
from point of interest on the Earth
Epicenter
o
Epicentral
Distance
Epicenter
Station
Focus
63
Station
1o = 112 km
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HYPOcentral Distance
• Direct distance from Focus
to Station of interest
Epicentral Distance
Epicenter
Fault
Rupture
Focal
Depth
Focus
64
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Foreshocks/Aftershocks
• Events of shaking before/after the main EQ event
Size
Main Shock
Time
Foreshocks
65
Aftershocks
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Faults
• Planes along which slip takes place
Dip Slip Faults
Strike Slip Faults
Left
Lateral
Normal
Reverse
66
Right
Lateral
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When
Earthquakes occur…
67
“We cannot predict the likely time accurately…”
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Earthquake fFrequency can be measured ..
No. Earthquakes, N, with M > m
100000
Data
10000
Fit
1000
Richter relationship
100
10
1
4
5
6
7
8
9
Magnitude, m
68
Average Number of Earthquakes Worldwide each Year
Seismic
Instruments
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Schematic of Early Seismograph
• Horizontal shaking
Magnet
String
Pendulum Bob
Support
Pen
Rotating Drum
Chart Paper
Direction of
Ground Shaking Recorded
70
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Schematic of Early Seismograph…
• Vertical shaking
Spring
Support
Rotating Drum
Pen
Direction of Vertical
Earthquake Shaking
Magnet
Pendulum Mass
71
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Inertial Seismometre
• Spring–mass system
Mass m
Sensor
Spring k
• Tune m, c and k ::
z( t )  ut 
u t 
t 
u
72
Damping c
Displacementmeter
Velocitymeter
Accelerometer
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Instruments
• Measure only translations
• Nomenclature
– Seismometre
• Sensor
– Seismograph
• Sensor + Recording Device + Time Device
 Records Displacement versus Time
– Seismoscope
• Instrument
 Records Peak Displacement
– Seismogram
• Graph or Record
 Obtained from a Seismograph
73
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Instruments…
• Classification
– Seismographs
• Low Amplitude Vibrations (long distance events)
• Displacement
 Ranger SS-1
– Strong Motion Instruments
• High Amplitude Vibrations (near-field strong events)
• Acceleration
• Examples
– Digital
• Digital Strong Motion Accelerograph (DSA-1, -3)
• Solid State Accelerograph (SSA-1, -2)
– Analog
• Strong Motion Accelerograph (SMA-1, SMA-2, SMA-3)
74
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Instruments…
• Strong Motion Instrument Arrays in India
Kangra Array
Uttar Pradesh Array
Shillong Array
75
!!
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Basics on
Seismic Waves
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Seismic Waves
• Arrival at a site
Structure
Surface Waves
Soil
Body Waves
Fault
Rupture
77
EQ
Geologic Strata
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Seismic Waves…
• Body Waves
P-Waves
Push and pull
Extension
S-Waves
78
Compression
Direction of
Energy Transmission
Up and down
Side to side
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Seismic Waves…
• Surface Waves
Love Waves
Sideways in horizontal plane
Direction of
Energy Transmission
Rayleigh Waves
79
Elliptic in vertical plane
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Body
Waves…
80
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Seismic
Waves
…
81
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Typical Shaking at a Site
Priestley et al
82
Locating the Epicenter
• Different arrival times
P
S
P-waves : 1.5-8 km/sec
S-waves : 60-70% of P-waves (1-5 km/sec)
• Speeds may vary
83
– Ratio between average speeds of P and S waves
is quite constant!
– Time-delay between arrival of P-and S-waves
is used to estimate location of epicenter
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Locating the Epicenter…
• Estimates
– Arrival times of P and S waves
– Wave velocities in the region
Epicenter
Station
Focal Distance d
Focus
VP  VS
d
d
 t 

VS VP
t
d  1
1

V
V
S
P
Approximate Distance (km) = t  8 km/s!
84
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Epicenter ...
85
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Triangulation…
86
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Locating the Epicenter…
• Can only “estimate” location
Station 3
Station 1
Station 2
87
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Time elapsed after start of EQ
(sec)
Locating the Epicenter…
88
A
B
C
Arrival of
S-Wave
Arrival of
P-Wave
Distance from Earthquake (km)
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Earthquake
Magnitude
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Earthquake Magnitude
• Quantitative measure of
physical shaking generated by the EQ
 Size of the Earthquake
• Ways of measuring
– Motion
– Energy
90
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Earthquake Magnitude…
• Charles Richter (1935)
– used amplitude of body waves on seismograms to
measure amount of energy released in an EQ
10 sec
Amplitude
91
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Richter Magnitude (ML)
• Definition
– Log10 (Max. Amplitude in microns)
– Wood-Anderson Seismograph
– 100 km from Epicenter
10mm
Time
100 km
Epicenter
Station
• Measurement depends on
92
– EQ size
– Epicentral distance
– Instrument type
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RICHter Magnitude…
93
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RICHter Magnitude…
• Scale is logarithmic
• No upper or lower limits
– Can even be negative
– Largest EQ recorded is 8.9!
• Correction for distance
– so that it has a unique value for a given event
94
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RICHter Magnitude…
• Weakness
– Does not depend on duration of shaking
– Saturates with length of fault
– Saturates with energy
Station
?
• 2001 Bhuj EQ
95
– Magnitude 6.9 (ML) versus 7.7 (MW)
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Many Magnitude Scales
• ML : Local Magnitude
– To describe local earthquakes within 500 km distance
• Mb : Body or P-wave Magnitude
– Determined using P-wave amplitude
• MS : Surface-wave Magnitude
– Determined using Rayleigh wave amplitude of time period >20s
– Commonly reported magnitude superseding ML
• Mw : Moment Magnitude
96
– Determined using rupture area, slip, and rock strength
– More accurate measurement of energy released
– Preferred by scientists
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Many Magnitude Scales…
• Saturation of Magnitude Scales
Mw
MS
Magnitude
ML
Mb
4
97
6
8
10
Moment Magnitude Mw
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Seismic Energy
• Amount of energy radiated by an EQ
• Energy released
– About 30 times, if ML goes up by 1
Log10E
= 11.8 + 1.5M, where E (ergs)
• M4.0 EQ
= Small nuclear weapon of 1000 ton yield!
98
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Seismic Energy
1E+27
Chile 1960 (M9.5)
1E+26
Alaska 1964 (M9.2)
1E+25
Annual Global Seismicity
Energy (Ergs)
1E+24
1E+23
Annual Stable
Continental Seismicity
1E+22
1E+21
1 megaton nuclear bomb
Hiroshima
1E+20
1E+19
Tornado
1E+18
1E+17
1E+16
4
5
6
7
8
9
10
Moment Magnitude
99
Bolt, 1993
Global Occurrence of EQs
Effects
Estimated
Number
per Year
1.0-3.0
Generally not felt but recorded
3 000 000
3.1-4.0
Often felt, but only minor damage
50 000
4.1-6.0
Slight damage to building
15 000
6.1-6.9
Can be destructive where people live in
120
7.0-7.9
Major earthquake; causes major damages
20
8.0 or greater
Great earthquake;
Total destruction of nearby communities
1
Magnitude
100
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Magnitude versus Intensity
100 Watt
Bulb
Magnitude
Near
Bright
(100 lumens)
Normal
(50 lumens)
Dull
(20 lumens)
101
Intensity
Far
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Magnitude versus Intensity…
• Wattage
– is akin to EQ Magnitude
• Brightness
– is akin to EQ Intensity
102
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Earthquake
Intensity
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Earthquake intensity
• Qualitative measure of strength of shaking
manifested at a given place during the EQ
 Influence of the Earthquake
– Before seismographs, Italian seismologist G. Mercalli
and other European scientists classified earthquakes
by the damage they produced qualitatively
– Intensity Scale is a Roman numeral I-XII point scale
to rate
104
• Building damage
• Ground movements
• Human impact due to an earthquake
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Many Intensity scales
• 1883 : Rossi-Forel Scale
I-X
– De-Rossi and Forel
• 1902 : Mercalli Scale
I-XII
– Mercalli
• 1931 : Modified Mercalli Scale
I-XII

1897
Great
Assam
EQ
– Wood and Neumann
• 1956 : Modified Mercalli Scale
I-XII
(1956 Version)
– Richter
• 1964 : MSK Scale
I-XII
– Medvedev, Sponheuer, Karnik
105
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Many Intensity Scales…
• Newer Scales
– Not widely used yet
• 1998 European Macroseismic Scale
I-XII
 First proposed in 1981; modified in 1992, 1998
• Japan Meteorological Agency Scale
1-7
 Used in Japan and Taiwan
Arabic
Numerals!!!
106
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Shortened Mercalli Scale
•I
• II
• III
• IV
•V
• VI
• VII
107
Only instrument detect it
People lying down feel it
People on upper floors of building feel it,
but may not know that it is earthquake
People indoors will probably feel it ,
but those outside may not.
Nearly everyone feels it
and wakes up even if sleeping.
Everyone feels the quake
and it’s hard to walk.
It is hard to stand.
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Shortened mercalli scale…
• VIII
• IX
•X
• XI
• XII
108
People will not be able to drive cars.
Poorly built buildings may fall.
Chimneys may fall.
Most foundations are damaged.
The ground cracks.
Most buildings are destroyed.
Water is thrown out of rivers and lakes.
Rails are bent. Bridges and underground
pipelines are put out of service.
Most things are leveled.
Large objects may be thrown into the air.
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isoseismals
• 2001 Bhuj Earthquake
Meizoseismal
region
X
IX
VIII
VII
109
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What are types of
Earthquake
Ground Motions
110
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Types of EQ Ground Motions
• Low Amplitude Vibrations
– Long distance events
– Usually displacements
– Earth Scientists
Amplitude
Teleseismic Earthquake Recording
0
111
200
Surface Waves
S
PP
P
400
600
800
1000
1200 Time (s)
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Types of EQ Ground Motions…
• Strong Ground Motions
– Near-field ground motions
– Usually accelerations
– Engineers
0.3
PGA=0.32g
Accn. (g)
0.2
0.1
0
-0.1
-0.2
-0.3
0
112
10
20
30
40
50
Time (se conds)
60
70
80
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Characteristics
• Peak Ground Parameters
– Acceleration (PGA)
– Velocity (PGV)
– Displacement (PGD)
113
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characteristics…
• Maximum Recorded PGA and PGV
114
(Martinez-Pereira, 1999)
characteristics…
• Parameters…
– Duration of Significant Shaking
– Frequency Content
1985 Mexico Earthquake (SCT 1A; N90E)
0.5g
1940 Imperial Valley Earthquake (El Centro; S00E)
1971 San Fernando Earthquake (Pacoima Dam; N76W)
0
10
20
30
40
50
60
Time (sec)
1991 Uttarkashi Earthquake (Uttarkashi, N75E)
115
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characteristics…
• Influence of
– Magnitude of EQ
– Source mechanism
Fault
• Type of faulting
Fault
– Distance from source
– Soil/rock medium along travel path
– Local soil site, geology, topology, etc.,.
116
Attenuation
with Distance
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Typical Shaking at a Site
117
A schematic of Prof. Sekiya’s wire diagram
illustrating the 3-D motion
http://nisee.berkeley.edu/lessons/a_figure1.jpg
characteristics…
• Examples
118
From Dynamics of Structures
by A K Chopra, Prentice Hall
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Directivity Effects
119
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• Sites in direction of fault propagation experience short, and
intense shaking, while those in opposite direction have a
lower intensity and longer duration of shaking. (Bolt 1993)
Hazard Maps
120
• Sites in direction of fault propagation experience short, and
intense shaking, while those in opposite direction have a
lower intensity and longer duration of shaking. (Bolt 1993)
Hazard Maps
121
Far-Field versus
Near-Field Motions
122
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Near Field Strong Ground Motions
• Near-Field geometry
Direction of Propagation of Rupture
Fault Parallel
Motion
Epicenter
123
Fault Normal
Motion
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Far Field versus Near Field Motions
• Comparison
– Far Field
• Only disturbance reflected in ground motions
– Near Field
• Fault movements reflected in ground motions
124
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Far Field
versus
Near Field Motions…
• Ground motions
125
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Far Field
versus
Near Field Motions…
• Structural behaviour…
Near Field
126
Characteristic
Far Field
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How to address Near-Field Effect
• In general…
– Strictly follow the advanced seismic codes for design,
detailing and construction practices
• For all special structures
– Tall, long and important structures
– Perform collapse-load time history analyses
• Use a variety of recorded near-field ground motions
• Ensure no “whip-lash effect” on structures due to
large velocity and acceleration pulses
127
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Attenuation
Relations
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I versus PGA
• Peak Ground Accelerations (PGA)
0.3
PGA=0.32g
Accn. (g)
0.2
0.1
0
-0.1
-0.2
-0.3
0
MMI
PGA (g)
129
V
10
20
VI
0.03-0.04 0.06-0.07
30
40
50
Time (se conds)
60
70
80
VII
VIII
IX
X
0.10-0.15
0.25-0.30
0.50-0.55
>0.60
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Effect of distance
• Reduction with distance
1979 Imperial Valley
130
M~6.6 Earthquakes
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Soil Effects
131
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2b
2a
1
See Dr. Layer!
http://gmiller.ce.washington.edu/DrLayer/
http://iisee.kenken.go.jp/net/yokoi/methodology/StrongMotion.htm
132
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134
From Bruce Bolt
Hazard Maps
Niigata, 1964
http://www.ce.washington.edu/~liquefaction/html/what/what1.html
135
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Hazard Maps
136
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137
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Most design is based
on the accelerations in
these maps. The
horizontal accelerations
for Ahmedabad (Zone
II) are 0.16g horizontal
for a maximum
considered level of
shaking. They are one
half of this for design.
The accelerations need
to be modified for any
local site conditions
http://www.isr.gujarat.gov.in/maps.shtm
138
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I versus PGA…
Data 1
Guttenberg and Richter (1956)
log PGA = 0.333 I - 0.500
G-R (1956)
1.0
N (1954)
Neumann (1954)
T-B (1975)
T-B (1977)
log PGA = 0.308 I - 0.041
N (1977)
M -O'B (1977)
log PGA = 0.300 I - 0.014
Trifunac and Brady (1977)
PGA (g)
Trifunac and Brady (1975)
0.10
log PGA = 0.350 I - 0.435
Neuman (1977)
log PGA = 0.380 I - 0.560
Murphy and O'Brien (1977)
log PGA = 0.250 I + 0.250
140
0.010
4
5
6
7
MMI
8
9
10
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More Legends
http://www.sjusd.org/leland/teachers/sgillis/seismic/Earthquake_legends_article.pdf
Different cultures around the world have attempted to explain earthquakes in different
ways. Here are some legends about what makes the ground shake!
India: The Earth is held up by four elephants that stand on the back of a turtle. The
turtle is balanced on top of a cobra. When any of these animals move, the Earth
trembles and shakes.
Assam (Between Bangladesh and China): There is a race of people living inside the
Earth. From time to time, they shake the ground to find out if anyone is still living on
the surface. When children feel a quake, they should shout "Alive, Alive!" so the people
inside the Earth will know they are there and stop shaking.
Mexico: El Diablo, the devil, makes giant rips in the Earth from the inside. He and his
devilish friends use the cracks when they want to come and stir up trouble on Earth.
Siberia: The Earth rests on a sled driven by a god named Tuli. The dogs who pull the
sled have fleas. When they stop to scratch, the Earth shakes.
Japan: A great catfish, or namazu, lies curled up under the sea, with the islands of
Japan resting on his back. A demigod, or daimyojin, holds a heavy stone over his head
to keep him from moving. Once in a while, though, the daimyojin is distracted, the
namazu moves, and the Earth trembles.
Mozambique: The Earth is a living creature, and it has the same kinds of problems
people have. Sometimes, it gets sick with fever and chills and we can feel its shaking.
More Legends
http://www.sjusd.org/leland/teachers/sgillis/seismic/Earthquake_legends_article.pdf
Greece: According to Aristotle, and also to William Shakespeare in a play called Henry IV, strong, wild
winds are trapped and held in caverns under the ground. They struggle to escape, and earthquakes are the
result of their struggle.
Belgium: When people on Earth are very, very sinful, God sends an angry angel to strike the air that
surrounds our planet. The blows produce a musical tone that is felt on the Earth as a series of shocks.
American Indian: Once a Chickasaw chief was in love with a Choctaw princess. He was young and
handsome, but he had a twisted foot, so his people called him Reelfoot. When the princess' father refused to
give Reel foot his daughter's hand, the chief and his friends kidnapped her and began to celebrate their
marriage. The Great Spirit was angry and stomped his foot. The shock caused the Mississippi River to
overflow its banks and drown the entire wedding party. (Reel foot Lake, on the Tennessee side of the
Mississippi River, was formed as a result of the New Madrid earthquake of 1812.)
West Africa: The Earth is a flat disk, held up on one side by an enormous mountain and on the other by a
giant. The giant's wife holds up the sky. The Earth trembles when he stops to hug her.
India: Seven serpents share the task of guarding the seven sections of the lowest heaven. The seven of them
also take turns holding up the Earth. When one finishes its turn and another moves into place, people on the
Earth may feel a jolt.
Latvia: A god named Drebkuhls carries the Earth in his arms as he walks through the heavens. When he's
having a bad day, he might handle his burden a little roughly. Then the Earth will feel the shaking.
Colombia: When the Earth was first made, it rested firmly on three large beams of wood. But one day the
god Chibchacum decided that it would be fun to see the plain of Bogotá underwater. He flooded the land, and
for his punishment he is forced to carry the world on his shoulders. Sometimes he's angry and stomps,
shaking the Earth.
MSK Intensity Scale (1964 Version)
• Russian Scientists
– Medvedev, Sponheuer and Karnik
• Types of Structures (Buildings)
– Structure A
Buildings in field stone, rural structures,
adobe houses, clay houses
– Structure B
Ordinary brick buildings, buildings of large block
and prefabricated type, half timbered structures,
buildings in natural hewn stone
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– Structure C
Reinforced concrete buildings, well-built wooden
structures
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MSK Intensity scale (1964 version)…
• Definition of quantity
– Single, few
– Many
– Most
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: ~ 5%
: ~ 50%
: ~ 75%
MSK Intensity scale (1964 version)…
• Classification of damage to buildings
– Grade 1 : Sight damage
• Fine cracks in plaster, fall of small pieces of plaster
– Grade 2 : Moderate damage
• Small cracks in walls, fall of fairly large piece of
plaster, pantiles slip off, cracks in chimneys, parts
of chimneys fall down
– Grade 3 : Heavy damage
• Large cracks in walls, fall of chimneys
– Grade 4 : Destruction
• Gaps in walls, parts of buildings may collapse,
separate parts of the building lose their cohesion,
inner walls collapse
– Grade 5 : Total damage
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• Total collapse of buildings
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MSK Intensity scale (1964 version)…
• Arrangement of the Scale
– Introductory letters are used in paragraphs
throughout the scale as follows:
(a) Persons and surroundings
(b) Structures of all kinds
(c) Nature
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MSK Intensity scale (1964 version)…
MSK Intensity Scale
I. Not noticeable
(a) The intensity of vibrations is below the limit of sensibility; the
tremor is detected and records by seismographs only.
II. Scarcely noticeable (very slight)
(a) Vibration is felt only by individual people at rest in houses,
especially on upper floors of buildings.
III. Weak, partially observed only
(a) The earthquake is felt indoors by a few people, outdoors only in
favourable circumstances. The vibration is like that due to the
passing of a light truck. Attentive observers notice a slight
swinging of hanging objects.
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MSK Intensity scale (1964 version)…
IV. Largely observed
(a) The earthquake is felt indoors by a few people outdoors by
few people. Here and there people awake, but no one is
frightened. The vibration is like that due to the passing of a
heavily loaded truck. Windows, doors, and dishes rattle. Floors
and walls creak. Furniture begins to shake. Hanging objects
swing slightly. Liquids in open vessels are slightly disturbed.
In standing motor cars the shock is noticeable.
(b)
(c)
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MSK Intensity scale (1964 version)…
V. Awakening
(a) The earthquake is felt in doors by all, outdoors by many.
Many sleeping people awake. A few run outdoors. Animals
become uneasy. Buildings tremble throughout. Hanging
objects swing. Pictures knock against walls or swing out of
place. Occasionally pendulum clocks stop. Unstable objects
may be overturned or shifted. Doors and windows are thrust
open and slam back again. Liquids spill in small amounts
from well-filled open containers. The sensation of vibration is
like that due to a heavy object falling inside the building.
(b)
(c) Slight waves on standing water; sometimes change in flow of
springs.
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MSK Intensity scale (1964 version)…
VI. Frightening
(a) Felt by most indoors and outdoors. Many people in buildings
are frightened and run outdoors. A few persons lose their
balance. Domestic animals run out of their stalls. In many
instances, dishes and glassware may break, books fall down,
pictures move, and unstable objects overturn. Heavy furniture
may possibly move and small steeple bells may ring.
(b) Damage of Grade 1 is sustained in single buildings of Type B
and in many of Type A. Damage in some buildings of Type A
is of Grade 2.
(c) Cracks up to widths of 1cm possible in wet ground; in
mountains occasional landslips; change in flow of springs and
in level of well-water.
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MSK Intensity scale (1964 version)…
VII. Damage to buildings
(a) Most people are frightened and run outdoors. Many find it
difficult to stand. The vibration is noticed by persons driving
motorcars. Large bells ring.
(b) In many buildings of Type C, damage of Grade 1 is caused; in
buildings of Type B, damage is of Grade 2. Most buildings of
Type A suffers damage of Grade 3, some of Grade 4. In single
instances, landslips of roadway on steep slopes; cracks in roads;
seams of pipelines damages; cracks in stone walls.
(c) Waves are formed on water, and is made turbid by mud stirred
up. Water levels in wells change, and the flow of springs
changes. Sometimes dry springs have their flow restored and
existing springs stop flowing. In isolated instances, parts of
sandy or gravelly banks slip off.
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MSK Intensity scale (1964 version)…
VIII. Destruction of buildings
(a) Fright and panic; also persons driving motor cars are
disturbed. Here and there branches of trees break off. Even
heavy furniture moves and partly overturns. Hanging lamps
are damaged in part.
(b) Most buildings of Type C suffer damage of Grade 2, and few
of Grade 3. Most buildings of Type B suffer damage of Grade 3.
Most buildings of Type A suffer damage of Grade 4. Many
buildings of Type C suffer damage of Grade 4. Occasional
breaking of pipe seams. Memorial and monuments move and
twist. Tombstones overturn. Stone walls collapse.
(c) Small landslips in hollows and on banked roads on steep
slopes; cracks in ground upto widths of several centimeters.
Water in lakes become turbid. New reservoirs come into
existence. Dry wells refill and existing wells become dry. In
many cases, change in flow and level of water is observed.
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MSK Intensity scale (1964 version)…
IX. General damage to buildings
(a) General panic; considerable damage to furniture. Animals run
to and fro in confusion, and cry.
(b) Many buildings of Type C suffer damage of Grade 3, and a
few of Grade 4. Many buildings of Type B show a damage of
Grade 2 and a few of Grade 5. Many buildings of Type A suffer
damage of Grade 5. Monuments and columns fall.
Considerable damage to reservoirs; underground pipes partly
broken. In individual cases, railway lines are bent and roadway
damaged.
(c) On flat and overflow of water, sand and mud is often observed.
Ground cracks to widths of up to 10 cm, on slopes and river
banks more than 10 cm. Furthermore, a large number of slight
cracks in ground; falls of rock, many land slides and earth
flows; large waves in water. Dry wells renew their flow and
existing wells dry up.
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MSK Intensity scale (1964 version)…
X. General destruction of buildings
(a)
(b) Many buildings of Type C suffer damage of Grade 4, and a
few of Grade 5. Many buildings of Type B show damage of
Grade 5. Most of Type A have destruction of grade 5. Critical
damage to dykes and dams. Severe damage to bridges. Railway
lines are bent slightly. Underground pipes are bent or broken.
Road paving and asphalt show waves.
(c) In ground, cracks up to widths of several centimeters,
sometimes up to 1 meter. Parallel to water courses occur broad
fissures. Loose ground slides from steep slopes. From river
banks and steep coasts, considerable landslides are possible. In
coastal areas, displacement of sand and mud; change of water
level in wells; water from canals, lakes, rivers, etc., thrown on
land. New lakes occur.
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MSK Intensity scale (1964 version)…
XI. Destruction
(a)
(b) Severe damage even to well-built buildings, bridges, water
dams and railway lines. Highways become useless.
Underground pipes destroyed.
(c) Ground considerably distorted by broad cracks and fissures,
as well as movement in horizontal and vertical directions.
Numerous landslips and falls of rocks. The intensity of the
earthquake requires to be investigated specifically.
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MSK Intensity scale (1964 version)…
XII. Landscape changes
(a)
(b) Practically all structures above and below ground are greatly
damaged or destroyed.
(c) The surface of the ground is radically changed. Considerable
ground cracks with extensive vertical horizontal movements
are observed. Falls of rock and slumping of river banks over
wide areas, lakes are dammed; waterfalls appear, and rivers are
deflected. The intensity of the earthquake requires to be
investigated specially.
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