Earthquakes are caused by the movement of tectonic plates deep within the Earth. As the plates shift and grind against each other, stress builds until it is suddenly released in the form of seismic waves. When these waves reach the Earth's surface, it causes the ground to shake violently. This shaking can damage buildings and infrastructure. Well-designed earthquake resistant structures have symmetrical and regular shapes, are tied together through strong foundations and interconnecting walls, and avoid projections and architectural features to withstand seismic activity without collapsing.

3. Earthquake :Definition
 A tremor on the surface of the Earth, sometimes
severe and devastating, which results from shock
waves generated by the movement of rock masses deep
within the Earth, particularly near boundaries of
tectonic plates.

4. Earthquake: Causes
 Outer Layer of Earth: Made up of layers called
Lithospheric Plates or Tectonic Plates
 These Plates are moving (few mm every year) due to
the movement of the molten Magma inside the Earth.
 These movement causes changes on Earth’s Surface.

8. • Plate boundaries get
interlocked when they slide
past each other due to
friction.
• The rest of the plates keep
moving giving rise to
tension in the plates.
• When the force moving the
plates overcome the friction,
Energy is released causing
the earth to shake at that
Point (Focus).
• The energy gives rise to
Seismic Waves which shake
the earth as they move
outward through it.
• When they reach the earth’s
surface, they shake the
ground and anything on it.

10. 1. Shaking and Ground Rupture
• Ground rupture is a visible breaking
and displacement of the Earth's
surface along the trace of the fault.
• Ground rupture is a major risk for
large engineering structures such
as dams, bridges and nuclear power
stations .
• Careful mapping of existing faults are
required to identify the breakage of
the ground surface within the life of
the structure.

11. 2. Landslides
 Earthquakes, along with
severe storms, volcanic
activity, coastal wave
attack, and wildfires, can
produce slope instability
leading to landslides, a
major geological hazard.
Landslide During the 2001 El Salvador earthquake

12. 3.Soil Liquefaction
 Soil liquefaction occurs
when, because of the
shaking, water-
saturated granular mate
r-ial (such as sand)
temporarily loses its
strength and transforms
from a solid to a liquid.
 Soil liquefaction may cause
rigid structures, like
buildings and bridges, to
tilt or sink into the
liquefied deposits. Sinkage of Structures during the 1964
Alaska Earthquake

13. 4. Tsunami
 Tsunamis are long-
wavelength, long-period
sea waves produced by the
sudden or abrupt
movement of large
volumes of water
 Large waves produced by
an earthquake or a
submarine landslide can
overrun nearby coastal
areas in a matter of
minutes.

14. Greatest Challenge Faced By a Civil Engineer

15. Effect of Earthquake on Buildings
 When the ground moves, The
building is thrown backward and
the top of the building (usually
roof) experiences a force called
inertia force.
 More mass mean higher inertia
force, therefore lighter buildings
sustain earthquake better.
 The inertia force is transferred to
the ground via the columns.
 Columns tend to come back to their
original positions, so an internal
force is developed.
 So as a result floor slabs, walls,
columns and foundations are
affected due to the above forces.

16.  Earthquake causes shaking
in all directions (i. e. along
the horizontal as well as
vertical direction.)
 All structures are
designed to carry the
gravity loads (i. e its own
weight) downwards.
 The vertical acceleration
during shocks have little
effect.
 Horizontal Shaking is
much of a concern.

17. Basic Features OF Earthquake
resistant Structures
 A building should survive a rare, very severe
earthquake by sustaining significant damage but
without globally collapsing.
 It should remain operational for more frequent, but
less severe seismic events.

18. Concrete
 Not very Earthquake Resistant
 Extremely strong under Compression but very weak
under Tension
 Thus cracks are caused during Earthquake
 Concrete structures are reinforced with steel rods as
steel is strong under tension.
 Pre stressed concrete is also used.

20. Foundations
 Foundations for concrete and masonry structures
should be excavated to the same level throughout the
building and should be as far as possible.
 The superstructure should be thoroughly tied up
to the foundation using reinforcements to offer
maximum resistant against sliding at that level.
 Isolated base Foundations are much in use
nowadays.

22. Body
 The walls should be as light in weight as possible and
made up of light weight concrete.
 Stronger walls should be designed with reinforced rather
than plain concrete.
 Continuity of cross walls should be maintained as far as
possible in such a way that different parts of the building
behave as integrals of the same structure.
 In masonry walls, keys (bricks and stones) should be
inserted in a proper style during each course so that the
danger of sliding apart the horizontal joints is minimized.
 Strongest mortars preferably cement sand mortars should
be used for masonry works in seismic regions.

23. The Roof
 Flat RCC roofs give better resistance to earthquake
shocks as compared to sloping roofs.
 Even in flat roofs when slates and corrugated sheets
are used care should be taken that no lateral stresses
are developed.
 Projections above or beyond the roof surface such as
chimneys, should be avoided or kept to a minimum.

24. Choice of site
 Mostly concerned with the Stability of the ground.
 Stability of slopes: Hill slopes are likely to slide during
shock. Stable Slopes should be chosen.
 Loose sand Or sensitive clays: During shocks they
would lead to large unequal settlement and damage to the
building. If the loose cohesionless soils are saturated with
water, they loose their shear resistance altogether during
shaking and become liquefied.
 Soil particles undergo a lot of compaction during seismic
shock thereby causing sinkage.
 Structures built on loose soil or sediments will have to
withstand a greater risk as compared to those on solid bed
rocks(already compacted) on the same region.

25. Sinkage of Structures

26. General Plan of building
 Symmetry: The whole
building as a whole or its
various blocks should be
kept symmetrical about
both axes. Asymmetry
leads to torsion during
shocks. (Fig
Alongside)Symmetry is
also required in placing
and sizing of doors and
windows.

27. • Regularity: Simple Rectangular shapes behave better
during shocks than shapes with projections. It is desirable
to restrict the length of the block to three times its
width as torsional effect is more pronounced in
narrow rectangular blocks.
• Separation of blocks: Large buildings are separated into
several Blocks s o as to obtain symmetry as well as
regularity.
• Simplicity: Large cornices, vertical or horizontal
cantilever projections etc. are considered dangerous from
seismic point of view. When Ornamentation is insisted it
should be reinforced with steel, which should be
properly embedded to the main structure.

28.  Enclosed area: A small
building enclosure with
properly interconnected
walls are more resistant
to earthquakes.
For larger panels or thinner
walls, Framing elements
should be introduced.

29. General Conclusion
 All parts of the same building – the foundations,
superstructure and the roof should be firmly tied
together so that the entire structure acts as a unit
during a shock.
 As far as possible uniform height should be given to
the structure.
 Architectural fancies like domes, cantilevers, arches
should be avoided as far as possible. When deemed
absolutely essential they should be designed with extra
care.