Major Earthquake Hazards and critical issues

1. Earthquake Hazards: Effect and
its Mitigation
Dr. J. N. Jha
Professor and Head (Civil Engineering)
Guru Nanak Dev Engineering College, Ludhiana

2. Tectonic hazards: earthquakes
 About 500,000 quakes occur every year: About 100 are
potentially dangerous
(Magnitude> 6 on Richter Scale )
 On an average 2 major quakes occur annually
(Magnitude> 8 on Richter Scale )
 Very large quakes occur perhaps once in a decade:
Releases nearly all the Earth’s seismic energy
 90% of the seismic energy released between 1900 &
1975 was by 10 great quakes only.
 Energy released during the 2001 Bhuj (India) earthquake
is about 400 times (or more) that released by the 1945
Atom Bomb dropped on Hiroshima!!

3. Tectonic hazards: earthquakes
 Over 40 countries are under threat from major
destructive quakes
 The biggest losses occur where major quakes
coincide with concentrations of people and
structures
 Kobe earthquake in the year 1999 resulted in
economic losses of US$ 200 bn
 Gujarat earthquake in the year 2001 may have
affected over 100,000 people

4. List of Major Historic Earthquakes
Year Location Deaths Magnitude
1556 China 5,30,000 8.0
1906 San Francisco 700 7.9
1960 S. Chile 2,230 9.5
1964 Alaska 131 9.2
1976 China 7,00,000 7.8
1985 Mexico City 9,500 8.1
1989 California 62 7.1
1995 Kobe 5,472 6.9
2001 Gujarat, India 16480 6.9
2004 Sumatra, Indonesia 2,30,210 9.3
2005 Pakistan 75000 7.6
2010 Haiti 46,000- 316,000 7.0
2011 Japan 15760 9.0

6. Some Past Earthquakes in India

7. 9.6
9.4
9.2
9
8.8
8.6
8.4
8.2
8
7.8
Great (M > 8) Earthquakes Since 1900
1900 1920 1940 1960 1980 2000 2020
Magnitude
Year
Chile1906
List of major historic earthquakes

8. Where do earthquakes occur?
Source: wikipedia

13. Tectonic hazards: Critical issues
 Seismic risk maps are not available for most of the
regions
 All earthquakes do not occur along plate
boundaries
 Precise prediction of earthquake (date and location
of earthquake ) not possible even today.
 Vulnerability to earthquakes has increased
dramatically
 More damages due to earthquake is occurring
because of increasing urbanization

14. Factors determining the destructiveness of a
 Size of quake
 Distance from epicenter
 Depth of quake
 Duration of shaking
 The local geology
 Meteorological
conditions
 Construction
practice
 Building code
enforcement
quake?
Earthquake damage in downtown Port-au-Prince
(Source: wikimedia)

15. 15
Major Earthquake Hazards
 Ground Motion: Shaking of structures results in damage or
total collapse
 Liquefaction: Happens in loose saturated cohesionless soils in
which the firm soil is converted into a fluid state which has
no shear strength and thus structures found on these soils fail
due to loss of bearing capacity of the ground
 Landslides: Vibrations during earthquake trigger large slope
failures
 Fire, Dust and Pollution : Indirect effect of earthquakes (large
scale damage triggered by EQ to gas pipe line and power
lines)
 Tsunamis: large waves created by the instantaneous
displacement of the sea floor during submarine earthquakes

16. Earthquake Destruction: Ground Shaking
Frequency of shaking differs for different seismic waves.
High frequency body waves shake low buildings more.
Low frequency surface waves shake high buildings more.
Intensity of shaking also depends on type of subsurface material.
Unconsolidated materials amplify shaking more than rocks do.
Buildings respond differently to shaking depending on the
construction styles and materials
-Wood is more more flexible, holds up well
-Earthen materials, unreinforced concrete are very vulnerable to
shaking.

17. Different Types of Waves
Arrival of Seismic waves at site

19. 19
Earthquake Destruction: Ground Shaking
Collapse of Buildings
Image of Bachau in Kutch region of Gujarat after earthquake

20. 20
Earthquake Destruction: Ground Shaking
Building design: Buildings that are not designed for earthquake loads suffer more
Image of a collapsed building in Ahmedabad during Bhuj earthquake

21. 21
Earthquake Destruction: Ground Shaking
Causes failure of lifelines
Source: google images

22. 22
Earthquake Destruction: Landslides
La Conchita, California- landslide and debris flow in1995 Source: wikipedia

23. Alaska Earthquake 1964: Major landslide

25. 25
Annual Landslide Costs
Global: US$ 10-20 Billion
0 1 2 3 4
Norway
New Zealand
Sweden
Canada
Spain
Ex USSR
China
India
USA
Italy
Japan
Country
Annual Landslide Cost (1990 US$ Billion)
Source: wikipedia

26. 26
Earthquake Destruction: Liquefaction
Buildings founded on saturated cohesionless soils are
vulnerable – Nigata, JAPAN 1964
Source: http://www.ce.washington.edu

29. 29
Earthquake Destruction: Liquefaction
Flow failures of structures are caused by loss of strength of underlying soil
Nishinomia Bridge 1995 Kobe earthquake, Japan

30. Earthquake Destruction: Liquefaction
Sand Boil: Ground water rushing to the surface due to liquefaction
Sand boils in Gujarat earthquake

31. Earthquake Destruction: Liquefaction
Source: wikipedia
Sand boils that erupted during the 2011 Canterbury earthquake, New Zealand.

32. Earthquake Destruction: Liquefaction
Lateral Spreading: Liquefaction related phenomenon
Source: wikipedia
Fissures caused by lateral spreading during Haiti earthquake

33. Earthquake Destruction: Liquefaction
Lateral spreading in the soil beneath embankment causes the embankment to be pulled apart,
producing the large crack down the center of the road.
Cracked Highway, Alaska earthquake,
1964
Source: google images

34. Earthquake Destruction: Liquefaction
Liquefied soil exerts higher pressure on retaining walls,which can
cause them to tilt or slide.
Source: google images

35. Earthquake Destruction: Liquefaction
Increased water pressure causes collapse of dams
Source: wikipedia

36. 36
Earthquake Destruction: Liquefaction
τ = c + σn tanø
τ = c’+ (σn –u)tanø’
During an earthquake,
static pore pressure `u’ may
increase by an amount udyn
τ = c’+ [(σn – (u + udyn)]tanø’
Let us consider a situation
when u + udyn= σn, then τ = c’
In cohesionless soil, c’= 0,
hence τ = 0

37. Earthquake Destruction: Fire
Earthquakes sometimes cause
fire due to broken gas lines,
contributing to the loss of life
and economy.
The destruction of lifelines and
utilities make impossible for
firefighters to reach fires started and
make the situation worse
eg. 1989 Loma Prieta
1906 San Francisco
2011 Japan
Source: International Business Times

38. 38
Earthquake Destruction: Fire
Northridge, 1994
Source: wikimedia

51. What is a tsunami?
 soo-NAH-mee or Harbor Wave is a Japanese word: tsu means harbor & nami means wave
 Definition: a ‘gravity wave’
in the sea (or other body of
water) produced by sudden
displacement of the seafloor
and the water column above
it
 Damaging tsunami waves
propagate much further than
damaging earthquake waves
 Tsunami can cause
simultaneous catastrophic
losses on opposite sides of
ocean basins

52. Earthquake Destruction: Tsunami
Tsunami Movement: ~600 mph in deep water
~250 mph in medium depth water
~35 mph in shallow water
Source: USGS public domain

53. 53
 At least 1500 (possibly
~3000) active volcanoes
 Around 50 erupt annually
 Over 82,000 people killed in
20th century
 Two eruptions killed over
20,000
 500 million people
threatened
 Perhaps 150 volcanoes
monitored
Earthquake Destruction: Volcanoes
Etna (Sicily)
Source: wikipedia

54. Earthquake Destruction: Volcanoes

55. Geo-morphological Changes
•Geo-morphological changes are often caused by an earthquake:
e.g., movements--either vertical or horizontal--along geological
fault traces; the raising, lowering, and tilting of the ground
surface with related effects on the flow of groundwater;
•An earthquake produces a permanent displacement across the
fault.
•Once a fault has been produced, it is a weakness within the rock,
and is the likely location for future earthquakes.
•After many earthquakes, the total displacement on a large fault
may build up to many kilometers, and the length of the fault may
propagate for hundreds of kilometers.

56. Mitigation Options
•Avoiding the hazard
•Building Earthquake resistant structures
•Ground Improvement
56

57. Mitigation Options: Avoiding hazard
Where the potential for failure is beyond the acceptable level and not
preventable by practical means, the locations of seismic threat can be
avoided and the structures should be relocated sufficiently far away
from the threat.
57

58. Mitigation Options: Earthquake Resistant Structures
Seismic demand should be less than the Computed capacity
‘Seismic demand’ is the effect of the earthquake on the structure.
‘Computed capacity’ is the structure’s ability to resist that effect
without failure.
Methods to increase capacity/ Decrease demand:
•Special Construction materials
•Special Foundation Techniques
•Special Construction Techniques
58

59. Building Earthquake resistant structures
Affect of Architectural Features on Building during EQ
Behaviour of Brick Masonary Houses during EQ
Effect of Earth Quake on RC Building

60. Affect of Architectural Features on Bld during EQ
 Size of the
Building
• Horizontal Movement is very large in tall building(Ht /Base)
• Damaging effects are many in long buildings
• Horizontal seismic force becomes excessive in case of building with large plan area (force
to be carried by column/wall)

61. Horizontal layout of the building
• Bld.With simple geometry in plan performs well during EQ
• Bld.With U,V,H & +shape sustains significant damage
• L-Shaped Building- Can be converted in simple plan into 2 rectangular block using
separation joint at the junction
• column/wall carries equally distributed load in case of simple plan

62. Vertical layout of buildings
• EQ force travels through the shortest path along
the height of the building
(Developed at different floor level of the bld.)
• Any discontinuity in this load transfer path results
in poor performance of the bld
• Bld. With vertical set backs causes a sudden jump
in earthquake force at the level of discontinuity
• Bld. With fewer column/wall in a particular storey
or with unusually tall storey tend to damage or
collapse
Contd………

63. Vertical layout of buildings
• Building with open ground story tends to damage during EQ
(2001 –Bhuj EQ-Ahmedabad)
• Unequal height of the column along the slope caused ill
effects like twisting and damage is more in shorter column
• Building with hanging and floating column have
discontinuities in load transfer path
• Building with RCC Walls that stops at an upper level gets
severely damaged

64. Affect of Architectural Features on Bld during EQ
 Suggestions
• Architectural features detrimental to EQ response of building should be avoided.
If not, they must be minimised
• In case irregular features included in building, higher level of engineering efforts is
required in structural design
• Decision made at the planning stage on building configuration are very important
• Building with simple architectural feature will always behave better during EQ

65. Behaviour of Brick Masonary Houses during EQ
 Behaviour of Wall
• All walls if joined properly to the adjacent wall ensures
good seismic performance
• Walls loaded in weak direction take advantage of the
good lateral resistance offered in their strong direction
• Walls need to be tied to the roof and foundation to
reserve their overall integrity

66. Simple Structural Configuration required for Masonary
Building
 Box Action in Masonary Bld.
• Separate block can oscillate independently and even
hammer each other (If too close during EQ)
• Adequate gap required betn such blocks
• Gap not necessary if horizontal projections in Bld are small
• An integrally connected inclined stair case slab acts like a
cross brace betn floors
• It transfers large horizontal forces at the roof and the lower
level (Area of Potential Damage)

67. Horizontal and Vertical Band necessary in Masonary
Building
Contd………

68. Effect of Earth Quake on RC Building
 Strength Hierarchy
• Building to remain safe during EQ :--
--Column should be stronger than Beam
--Foundation should be stronger than Column
--Connection between beams & Column and Columns & Foundation should not fail

69. Reinforcement and Seismic Design

70. Reinforcement and Seismic Design

71. Reinforcement and Seismic Design

72. Reinforcement and
Seismic Design

73. Reinforcement and Seismic Design

74. How do Beam Column Joins in RC bld Resist EQ
 EQ behaviour of Joints
 Three stage procedure for providing
horizontal ties in the joints

75. Soft Storey
Beam and
column in
the open
ground
storey are
required to
be
designed
for 2.5
times the
forces
obtained
from bare
frame
analysis

76. Special Construction Materials
These materials absorb a part of seismic energy and thereby reduces the
effect of earthquake on structure.
These materials are strategically used to modify the force–deformation
response of structural components and/or enhance their energy
dissipation potential.
Some of the special materials:
Rubber, lead, copper, brass, aluminum, stainless steel, fibre-reinforced
plastics and shape-memory alloys
76

77. Mitigation Options: Special Construction Techniques
Special construction techniques are adapted to reduce the seismic
demand on the superstructure by sharing the earthquake loads
through non-conventional structural elements.
Some of these Techniques Include:
•Base Isolation Systems
•Energy Dissipation Systems
•Active Control Systems
77

78. Base Isolation Systems
In base-isolated systems, the superstructure is isolated
from the foundation by certain devices, which reduce the
ground motion transmitted to the structure. These devices
help decouple the superstructure from damaging
earthquake components and absorb seismic energy by
adding significant damping .
78

79. Passive Energy Dissipation Systems
Various Energy Dissipating Devices (EDD) are used to dissipate
the seismic energy. These devices are like ‘add-ons’ to
conventional fixed-base system, to share the seismic demand
along with primary structural members.
79

80. Active Control Systems
They control the seismic response through appropriate adjustments within
the structure, as the seismic excitation changes. In other words, active
control systems introduce elements of dynamism and adaptability into the
structure, thereby augmenting the capability to resist exceptional
earthquake loads.
A majority of these techniques
involve adjusting lateral strength,
stiffness and dynamic properties of
the structure during the earthquake
to reduce the structural response
80

81. Mitigation Options: Ground Improvement
Earthquake damage is greater in poorer soil areas, and significant life and
property losses are often associated with soil-related failures.
Buildings and lifelines located in earthquake-prone regions, especially
structures founded upon loose saturated sands, reclaimed or otherwise
created lands, and deep deposits of soft clays, are vulnerable to a variety of
earthquake-induced ground damage such as liquefaction, landslides,
settlement, and ground cracking.
Recent experiences show that engineering techniques for ground
improvement can mitigate earthquake related damage and reduce losses.
81

82. Mitigation Options: Ground Improvement
Fundamental approaches of Ground Improvement to mitigate earthquake
damages are either to increase capacity of soil or to decrease the
earthquake demand on the soil using several techniques.
Increasing Capacity Decreasing Demand
Soil Densification
Providing drains for rapid
dissipation of pore pressures
Grouting
Soil Reinforcement
82

83. Ground Improvement: Soil Densification
Soil densification techniques:
•Compaction
•Vibro-replacement (Vibroflotation & Stone Columns)
•Blasting
•Grouting
•Compaction Piles
83

84. Field Compaction
Different types of rollers (clockwise
from right):
 Smooth-wheel roller
 Vibratory roller
• Pneumatic rubber tired roller
 Sheepsfoot roller
84

85. Dynamic Compaction
- pounding the ground by a heavy weight
Suitable for granular soils and landfilles
Pounder (Tamper)
Crater created by the impact
(to be backfilled)
Source: http://www.geoforum.com
85

86. Dynamic Compaction
Pounder (Tamper)
Mass = 5-30 tonne
Drop = 10-30 m
86
Source: http://www.geoforum.com

87. Dynamic Compaction
87
Source: http://www.geoforum.com

88. Ground Densification: Vibro-Compaction
Vibro-Compaction also knows as VibroFlotation is used to
densify clean, cohesionless soils. The action of the
vibrator, usually accompanied by water jetting, reduces
the inter-granular forces between the soil particles,
allowing them to move into a denser configuration,
typically achieving a relative density of 70 to 85 percent.
Compaction is achieved above and below the water table.
88
Source: http://www.geoforum.com

89. vibrator makes a hole
in the weak ground
hole backfilled ..and compacted Densely compacted stone
column
Vibroflotation
89
Source: http://www.geoforum.com

90. Vibroflotation
90
Source: http://www.geoforum.com

91. Ground Densification: Vibro-Compaction
91

92. Ground Densification: Blasting
• Generally used to improve density of silty sands-sandy gravels
(non-cohesive soils)
• Makes use of dynamic/undrained loading conditions to cause
liquefaction-induced settlement
• Sudden dynamic loading breaks cohesion and any cementation
• Shockwave temporarily liquefies soil layer
• Settlement occurs as excess pore water pressure approaches zero.
• Typical vertical strain between 2% and 10%
92

93. Ground Densification: Blasting
Aftermath of blasting
For densifying granular soils
93

94. Soil Densification: Grouting
Grouting is is a technique whereby a slow-flowing water/sand/cement mix is
injected under pressure into a granular soil.
The grout forms a bulb that displaces and hence densifies, the surrounding
soil.
Compaction grouting is a good option if the foundation of an existing
building requires improvement, since it is possible to inject the grout from the
side or at an inclined angle to reach beneath the building.
Jet grouting involves the injection of low viscosity liquid grout into the pore
spaces of granular soils. This creates hardened soils to replace loose
liquefiable soils.
94

95. Soil Densification: Compaction Grouting
Compaction Grouting
uses displacement to
improve ground
conditions.
A highly viscous
aggregate grout is
pumped in stages,
forming grout bulbs,
which displace and
densify the surrounding
soils.
Used for loose soils,
liquefiable Soils and
collapsible Soils
95

96. Soil Densification: Cement Grouting
Cement Grouting, also known as
Slurry Grouting, is the intrusion
of microfine cement slurry (fine
portland cement mixed with a
dispersant and larger quantities
of water) into fine sand and
finely cracked rock under
pressure
96

97. Jet Grouting
Grout is pumped through the rod and exits the horizontal nozzle(s) at high
velocity [approximately 200m/sec]. This energy breaks down the soil matrix
and replaces it with a mixture of grout slurry and in-situ soil (soilcrete). Jet
grouting is most effective in cohesionless soils.
97

98. Jet Grouting
98

99. Ground Densification: Deep soil mixing
Source: http://www.geoforum.com
Deep Mixing Method is the mechanical blending of the in situ soil with
cementitious materials using a hollow stem auger and paddle
arrangement. These materials could be Cement or Fly ash or Ground Blast
Furnace Slag or Lime or Additives or Combination of these. Soil mixing has
the ability to strengthen soft and wet cohesive soils in a very short time
period to permit many types of construction projects.
99

100. Ground Improvement: Vertical Drains
The installation of prefabricated
vertical drains provides shortened
drainage paths for the water to exit
the soil. Drainage remediation
methods mitigate liquefaction
hazards by enhancing the rate of
excess pore pressure dissipation.
The most common methods of
drainage remediation are through
the use of gravel, sand or wick
drains. Drains are suitable for silts
or clays.
100
Source: http://www.geoforum.com

101. Ground Improvement: Vertical Drains
Primary consolidation
settlement will already be
achieved during the
construction period by using
vertical drains
101

102. Earthquake drains
102

103. Earthquake Drains
SM
Earthquake Drains are prefabricated in the field to project specifications. The drain is fitted with a sacrificial
endplate. The completed drains are fed into the installation mandrel and driven to treatment depth. When the
mandrel is withdrawn, the endplate anchors in the soil leaving the drain in-place. 103

104. Earthquake Drains
• Dissipates excess pore pressures as they generate during a
seismic event
• Can be used to retrofit existing structures
• approximately one third the cost of traditional stone
columns
• installation times approximately one third to one half of
that for stone columns.
104

105. Earthquake drains
FINS: Transmit vibratory
motion to the soil for
densification
STEEL CASING: Protects
drain from driving stresses
PREFABRICATED
DRAIN
Figure 2.1: Cross section of casing and prefabricated drain
105

106. Earthquake drains
106

107. Earthquake drains
107
Source: google images

108. Geosynthetic Reinforced Soil Retaining walls
Seismic wave action in GRS
Wall
Geosynthetics allow for the movement of the
earth to pass through the reinforced soil mass
similar to a wave passing through a body of
water.
Once the wave passes, the water returns to its
original state. As the wave of ground
movement passes through the soil mass, the
geosyntetic reinforcement flexes with the
movement of the earth but returns to its
prequake position
108

109. Performance of GRS walls during earthquakes
Kobe , Japan - MW6.9
The wall was completed in 1992 for a total length was about 300 m. It was deformed and moved only slightly
during the devastating earthquake that occurred in Japan, while more than half of the wooden houses in front
of the wall collapsed totally. This type of geogrid-reinforced soil retaining wall was broadly employed to
reconstruct the damaged conventi onal type retaining walls after the earthquake since it performed so well.
109

110. Mechanically stabilized earth wall within a few meters of the primary fault
rupture. Although subjected to differential settlement, it suffered only minor
Turkey Earthquake of August 17, 1999
damage.
110

111. Koyna Bridge Abutment: GRS technique Employed
Rehabilitation of Koyna Bridge abutment in
Maharashtra, India, located on SH 78 in
seismic Zone-IV was done using geosynthetic
reinforced wall technique encapsulating the
cracked return wall.
The project was completed in the year1996 and
its performance in seismic Zone-IV, which is
vulnerable to frequent earthquake, is very
satisfactory in spite of repeated after shocks,
including recent ones
111

112. Forecasting Earthquakes: Earlier Methods
Strange Animal Behavior
Stress in the rocks causes tiny hairline fractures. Cracking of the rocks emits
high pitched sounds and minute vibrations imperceptible to humans but
noticeable by many animals.
Unusual Weather Conditions and Clouds
A few scientists claim to have observed clouds associated with a seismic
event, sometimes more than 50 days in advance of the earthquake.
Foreshocks
Foreshocks are minor tremors of the earth that precede a larger earthquake
originating at approximately the same location. Unusual increase in the
frequency of these foreshocks are sign for an earthquake.
Changes in water level
porosity increases or decreases with changes in strain, causing fluctuations in
ground water level
112

113. Forecasting Earthquakes: Recent Developments
Changes in Seismic Velocities
Earthquakes are often accompanied by temporal changes in seismic wave
velocities in the region
Radon Emission
Emission of radon gas as a quake precursor is recently being explored by the
geophysicists for developing a worldwide seismic early warning system
The Van Method
The method is based on the detection of "seismic electric signals" (SES) via a
telemetric network of conductive metal rods inserted in the ground.
Researchers have claimed to be able to predict earthquakes of magnitude
larger than 5 using this method.
Geodetic Measurements
Laser geodimeter measures changes in distance across the fault between
points. Changes in distances may indicate a precursor to an upcoming
earthquake. 113

114. Prediction of Earthquakes
Seismic hazard map of the San
Francisco Bay Area, showing the
probability of a major
earthquake occurring by 2032
114
Source: USGS public domain

115. First Successful Prediction
Earthquake prediction has taken a scientific turn in late 1970s.
The first successful prediction was made in China in winter 1975 for the city of Haicheng
(population about 1 million).
Scientists observed changes in land elevation and ground water levels in that region over
a period of time. A regional increase in foreshocks had triggered a low-level alert.
Based on the reports from scientists, Chinese officials had ordered the evacuation of the
city. On February 4, 1975, earthquake of magnitude 7.3 struck the region. Only very
small fraction (2,041 people) died in this event. The number of fatalities and injuries
would have exceeded 150,000 if no earthquake prediction and evacuation had been
made.
115

116. Acknowledgements
• The author wishes to acknowledge all the various sources used
during the preparation of this presentation which aided and
enhanced the quality either in the form of information, graph
data, figure, photo, or table.
Any Question ………..?
Thanks for your attention