structural dynamics

1. NAME : ANUPAM GOWDA MN
M.TECH 1ST YEAR
STRUCTURAL DYNAMICS
TOPIC: SEISMIC WAVES

2. SEISMIC WAVES:
Seismic waves are vibrations that travel through the Earth's crust.
They can be caused by natural events such as earthquakes or human
activities such as explosions.
Seismology is the study of the passage of elastic waves through the earth.
Earthquake seismology is the best tool to study the interior of the earth.
When an earthquake or explosion occurs, part of the energy released is as
elastic waves that are transmitted through the earth.
The waves are then detected and recorded by seismographs, which
measure, amplify and record the motion of the ground.
The information is then used to determine earthquake locations, the
subsurface structures and etc.

3. There are two main types of seismic waves: body waves and surface
waves.
Body waves travel through the Earth's interior and can be further
divided into two types:
P-waves
S-waves

4. Body Waves
1. P-waves
• These are the 1st waves to hit the seismographs
when an earth quake strikes.
• P-waves also known as primary waves or
compressional waves, are the fastest seismic
waves and can travel through solids, liquids, and
gases.
• Moves in the direction of wave propagation.
• Speed of propoghation1.5 – 13 km/s.
• They move in a back-and-forth motion, like a
slinky, and can cause buildings to vibrate up and
down.

5. • P-Waves
• P-waves, also known as primary waves, are a type of seismic wave
that travel through the Earth's interior. They are longitudinal waves,
meaning that they compress and expand the material they pass through
in the same direction as the wave is traveling. P-waves are the fastest
type of seismic wave, with speeds ranging from 5 to 8 km/s in the
Earth's crust.
• P-waves can travel through both solid and liquid materials, which
makes them useful for studying the Earth's interior. When they
encounter a boundary between different materials, they can be
refracted or reflected, providing valuable information about the
composition and structure of the Earth's layers.

6. There are two types of P waves:
Compressional and Dilatational.
• Compressional P waves cause particles to move back and forth in the
same direction that the wave is traveling.
• Dilatational P waves cause particles to move perpendicular to the
direction of the wave. These waves are important in understanding the
structure of the Earth's interior.

8. Surface Waves (Contd.,)
2. S-waves
• S-waves, also known as secondary waves or
shear waves, are slower than P-waves and can
only travel through solids.
• Motion is perpendicular to direction of wave
propagation
• Used in successful mapping of earth interiors,
• They move in a side-to-side motion, like a rope
being shaken, and can cause buildings to shake
from side to side.

9. Type of S Waves
• S waves, also known as secondary waves or shear waves, are one of the
two main types of seismic waves. They travel 1.7 times slower than P
waves and can only propagate through solid materials. Unlike P waves, S
waves move particles perpendicular to the direction of wave propagation,
causing rocks to shake side-to-side or up-and-down. This motion makes
them responsible for the damage caused by earthquakes.
• There are two types of S waves: horizontal S waves and vertical S waves.
Horizontal S waves move particles horizontally, while vertical S waves
move particles vertically. The amplitude of horizontal S waves is usually
larger than that of vertical S waves, making them more destructive.

10. Rayleigh Waves
• Rayleigh waves are a type of seismic
wave that travels along the surface of the
Earth.
• They are named after Lord Rayleigh, who
first studied them in detail.
• Rayleigh waves cause the ground to move
in an elliptical motion, with the largest
amplitude perpendicular to the direction
of travel.
• They have a slower velocity than other
types of seismic waves, but they can still
cause significant damage to buildings and
other structures.

11. Love Waves
• Love waves, on the other hand, are
another type of seismic wave that travel
along the surface of the Earth.
• They are named after Augustus Edward
Hough Love, who first described them
mathematically.
• Love waves cause the ground to move in
a horizontal motion, similar to the motion
of a snake.
• They have a faster velocity than Rayleigh
waves, but they also have a smaller
amplitude.

14. THANK YOU