Earthquake is one of the most destruct able natural disaster hence there is a need to learn about it.

1. Submitted by:
Himanshu Rajput(13363)
Mechanical Engineering Department
NIT Hamirpur

3. • An Earthquake is the result of a sudden release of
energy in the Earth’s crust that creates seismic
waves(vibrations).
• Earth’s crust is in constant motion because of
tectonic forces.
• Earth’s crust can store elastic energy.
• When forces exceed the elastic limits and structural
strength of the rocks, the rocks will break and/or
move producing vibrations that travel outward in all
directions.

4. The actual place underground where
the rocks break producing vibrations is
called the Focus.
 The place on the surface directly above
the focus is called the Epicenter.

6. PLATE TECTONICS
T h e c o n v e c t i v e f l o w s o f m a n t l e m a t e r i a l
c a u s e t h e c r u s t a n d s o m e p o r t i o n o f t h e
m a n t l e , t o s l i d e o n t h e h o t m o l t e n o u t e r
c o r e . T h i s s l i d i n g o f e a r t h ’s m a s s t a k e s
p l a c e i n p i e c e s c a l l e d t e c t o n i c p l a t e s .
T h e s u r f a c e o f t h e e a r t h c o n s i s t s o f
s e v e n m a j o r t e c t o n i c p l a t e s a n d m a n y
s m a l l e r o n e s . T h e s e p l a t e s m o v e i n
d i f f e r e n t d i r e c t i o n s a n d a t d i f f e r e n t
s p e e d s f r o m t h o s e o f t h e n e i g h b o u r i n g
o n e s .
T h e m o v e m e n t o f t e c t o n i c i s v e r y s l o w
b u t i n s o m e p l a c e s i t i s a s m u c h a s
a b o u t 5 c m p e r y e a r.

7. Earthquakes often occur when tectonic plate
collide.
What happens when plates collide? It depends how
the plates are moving when they meet:
When two plates collide head-on, they
push each other up and form mountains. That's how
the Himalayas and other great mountain ranges
(including the Rockies, long ago) were created.

9. FAULTS
 A f a u l t i s a f r a c t u r e w i t h i n s o m e
p a r t i c u l a r r o c k y m a s s i n s i d e t h e
e a r t h ' s c r u s t . T h e d e p t h a n d l e n g t h o f
f a u l t s v a r y g r e a t l y.
 F a u l t s m a y r a n g e i n l e n g t h f r o m f e w
m e t e r s t o m a n y k i l o m e t e r s a n d a r e
d r a w n o n a g e o l o g i c a l m a p a s
c o n t i n u o u s o r b r o k e n l i n e s .
E a r t h q u a k e s a r e c a u s e d b y a c t i v e
f a u l t s , t h a t i s , f a u l t s a l o n g w h i c h t h e
t w o s i d e s o f t h e f r a c t u r e m o v e w i t h
r e s p e c t t o e a c h o t h e r. S o , a n
e a r t h q u a k e i s c a u s e d b y t h e s u d d e n

11. Faults Are Classified According
to the Kind of Motion That
Occurs on them:
1. Strike slip fault
2. Dip slip fault

12. Shear Force:
A system of forces that operates against a body from different
sides. Makes a strike-slip fault. It is of two types:
STRIKE-SLIP FAULT

13. Strike-Slip Fault

14. Compression Force:
Forcepushing somethingtogether. Makes a reverse fault.
Dip-Slip Fault

15. Normal Fault Structures

16. Reverse Fault Structures

17. Originate atthe focusand travel outward inall
directions
 Foreshocks: small earthquakes thatcome
before a major earthquake.
 Aftershocks: Are adjustmentsin thecrust
after inearthquake.
o Smaller thanmainearthquake, but can
cause as much or more damage. They can
continuefor weeksto months. Not
every earthquake produces aftershocks.

18. Types of seismic waves:
1. Body waves -- travel through interior
2. Surface waves -- travel on surface of earth
Specific Body Waves
Primary or "P" Waves: Primary waves Highest velocity
Causes compression and expansion in direction of wave travel.
Secondary or "S" Waves: Secondary or shear waves
Slower than P waves but faster than surface waves.
Causes shearing of rock perpendicular to direction of wave propagation
Cannot travel through liquids
Surface Waves or "Love" (“L”) Waves
Cause vertical & horizontal shaking
Travel exclusively along surface of earth

20. Rayleigh Waves
The other kind of surface wave is the Rayleigh
wave, named for John William Strutt, Lord
Rayleigh, who mathematically predicted the
existence of this kind of wave in 1885. A
Rayleigh wave rolls along the ground just like a
wave rolls across a lake or an ocean. Because it
rolls, it moves the ground up and down, and
side-to-side in the same direction that the wave
is moving. Most of the shaking felt from an
earthquake is due to the Rayleigh wave, which
can be much larger than the other waves.

22. MEASUREMENT OF EARTHQUAKE
Earthquake waves are recorded by a seismograph
and the recording of waves on paper is called
seismogram.

23. MAGNITUDE OF AN EARTHQUAKE
Magnitude -- measure of energy released during earthquake.
There are several different ways to measure magnitude.
Most common magnitude measure is Richter Magnitude,
named for the renowned seismologist, Charles Richter.
RICHTER MAGNITUDE
Measure amplitude of largest wave on seismograph record.
Take into account distance between seismograph &
epicenter.

24.  Logarithmic numerical (NOT a physical)
scale.
 Increasing one whole unit on Richter
Scale represents 10 times greater
magnitude.
 Going up one whole unit on
Richter Scale represents about a 30 times
greater release of energy.

26. INTENSITY OF EARTHQUAKE
Intensity refers to the amount of damage
done in an earthquake.
Mercalli scale is used to express damage.
MODIFIED MERCALLI INTENSITY SCALE:
An estimate of the intensity based on
damage.
• A 12 point scale using roman numerals.
• Very dependent upon the quality of

28. The Secondary effects of
earthquakes include the
following:
Shaking and ground rupture
Landslides
Fires
Tsunami
Floods
Human impacts
Radiation Leakage
Soil liquefaction

29.  Intensity of Earthquakes forces
 Lack of strength and integrity in buildings
 Resonance and semi-resonance
 Lack of ductility and lack of detailing
MAIN CAUSES OF DAMAGE

30. RESONANCE= frequency content of the
ground motion is close to building's natural
frequency ,tends to increase or amplify
building response .Building suffers the
greatest damage from ground motion at a
frequency close or equal to its own natural
frequency

31. Landslide after
earthquake

32. The tsunami of the 2004 Indian Ocean

34. Ash cloud of Pinatubo during 1991 eruption

35. The objective of earthquake engineering is to foreseethe impact of
earthquakes on buildings and other structures and to design such
structures to minimize the risk of damage. Existing structures can be
modified by seismic retrofitting to improve their resistance to
earthquakes. Earthquake insurance can provide building owners
with financial protection against losses resulting from earthquakes.
Emergencymanagement strategies can be employed by a
government or organization to mitigate risks and preparefor
consequences.

37. The above slides gave us various aspects
related to earthquake. Now after these
slides we know what is earthquake and way
to measure its magnitude by Richter scale.
The various seismic waveforms and
Rayleigh waves. The slides also showed the
after effects of earthquake like landslides,
tsunami etc. and the destruction caused by
earthquake. In the end it was the
importance of Earthquake engineering.
Summary

38. THANK YOU