To study about the earthquake waves

1. SEISMIC WAVES
Saseetharan.d

2. Seismic waves
 Seismic waves are the waves of energy caused by the sudden
breaking of rock within the earth or an explosion. They are the
energy that travels through the earth and is recorded on
seismographs.
 There are several different kinds of seismic waves, and they all
move in different ways. The two main types of waves are body
waves and surface waves.

3. Faulting
Seismic waves

4. Types of Seismic Wave
 Body waves
 Primary waves (P-waves)
 Secondary waves (S-waves)
 Surface waves
 Love waves
 Rayleigh waves
 Particle motion of surface waves

5. Body Waves
P Waves (compression wave)
The first kind of body wave is the P wave or primary wave. This is the fastest kind of
seismic wave. The P wave can move through solid rock and fluids, like water or the liquid
layers of the earth. It pushes and pulls the rock it moves through just like sound waves push
and pull the air.





 3
/
4
2 



p
v

6. Body Waves
S wave (transverse wave)
The second type of body wave is the S wave or secondary wave, which is the second wave
you feel in an earthquake. An S wave is slower than a P wave and can only move through
solid rock. This wave moves rock up and down, or side-to-side.



s
v

7. Body Waves
Deformation of material
samples for determining
elastic moduli
Bulk modulus
 = P / (V/ V) 
Shear modulus
or „rigidity“
 = (F/A) / (L/L) 
Young´s or „stretch“
modulus E = (F/A)/ (L/L)
and Poisson ratio
 = (W/W) / (L/L) 
3

s
p
v
v





 3
/
4
2 



p
v



s
v

8. Surface Waves
Love Waves
The first kind of surface wave is called a Love wave, named after A.E.H. Love, a
British mathematician who worked out the mathematical model for this kind of wave
in 1911. It's the fastest surface wave and moves the ground from side-to-side.

9. Surface Waves
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.

10. January 26, 2001 Gujarat, India Earthquake (Mw7.7)
vertical
Rayleigh Waves
radial
Love Waves transverse
Recorded in Japan at a distance of 57o (6300 km)

11. Wave Period and Wavelength
Space
Time
wavelength 300 km
period 50 s
frequency = 1/period= 0.02 Hz
Velocity = Wavelength / Period
Velocity 6 km/s
x
t
wavelength
period

12. Period Wavelength
Body waves 0.01 to 50 sec 50 m to 500 km
Surface waves 10 to 350 sec 30 to 1000 km
Free Oscillations 350 to 3600 sec 1000 to 10000 km
Static Displacements
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