The document discusses earthquakes, including their causes, types, effects, and measurement. Earthquakes are caused by the sudden release of stress along faults within the earth's crust. They can be shallow, mid-focus, or deep, and cause both primary (P) waves and secondary (S) waves. The magnitude and intensity of quakes are measured using the Richter scale and Mercalli scale, respectively. Major quakes frequently occur at plate boundaries and have caused widespread damage throughout history.
2. Earthquakes
Types of Earthquakes
Anatomy of Earthquakes
Causes of Earthquakes
Waves of Earthquakes
Seismograph & Richter Scale
Distribution of Earthquakes
World Deadliest Earthquakes
Earthquakes in Pakistan
Effects of Earthquakes
Contents
3. It is the release of Internal Stress of Lithosphere
Shaking of Earth Crust
Earthquakes are also termed as Creep, Seismic Slip or it
may be Elastic Rebound depending upon the nature of
Movement
Earthquakes
4. With the sudden displacement and associated stress
release, the rocks snap back elastically to their previous
dimensions, this behavior is called Elastic Rebound.
Elastic Rebound
5. When movement along fault occur gradually and
smoothly it is called Creep
It is also called Seismic Slip
Seismic Slip
6. Generally there are following types of Earthquakes depending
upon their depth
a. Shallow Focus Earthquakes <70km
b. Mid Focus Earthquakes 70-300km
c. Deep Focus Earthquakes 300- upto 700km
On the basis of Magnitude Earthquakes can be classify as
a. Micro-Earthquakes
b. Macro-Earthquakes
Types of Earthquakes
7. Foreshocks
Epicenter
Hypocenter/Focus
After Shocks
Magnitude
a. Richter Scale
Intensity
a. Mercalli Intensity Scale
Anatomy of Earthquakes
8. Earthquakes are generally occurs due to the Plate
Movements or due to the Faults
90 percent of the world's earthquakes occur along plate
boundaries
The rocks are usually weaker and yield more readily to
stress
Causes of Earthquakes
11. Faults
Fault is a fracture or zone of fractures between two
blocks of rock
Faults allow the blocks to move relative to each other
This movement may occur rapidly, in the form of an
earthquake - or may occur slowly, in the form of creep
Faults may range in length from a few millimeters to
thousands of kilometers.
Normal Fault (Vertical Displacement due to Tension)
Fault Scrap (Steep, Straight Cliff like Feature)
Reverse and Overthrust Faults
12. There are 3 basic types of faults
1. Dip-Slip Fault
2. Strike-Slip Fault
3. Oblique-Slip Fault
Types of Faults
13.
14. 1. Dip-slip faults are inclined fractures where the blocks
have mostly shifted vertically. If the rock mass above an
inclined fault moves down, the fault is termed normal,
whereas if the rock above the fault moves up, the fault is
termed reverse.
A thrust fault is a reverse fault with a dip of 45 degrees or
less. Oblique-slip faults have significant components of
different slip styles.
2. Strike-slip faults are vertical (or nearly vertical) fractures
where the blocks have mostly moved horizontally. If the
block opposite an observer looking across the fault moves
to the right, the slip style is termed right lateral; if the block
moves to the left, the motion is termed left lateral.
15. Seismic energy travels through the crust in the form of
waves
The propagation velocity of seismic waves depends
upon the density and elasticity of the medium in which
seismic waves are penetrated
Seismic Waves are of two types
a) Body Waves
b) Surface Waves
Waves of Earthquakes
16. A body wave is a seismic wave that moves through the
interior of the earth
P and S waves are Body Waves
Each type of wave shakes the ground in different ways
Body Waves
17. P-Waves can travel through gases, solids and liquids
P-waves are produced by earthquakes and recorded
by seismometers
The name P-wave stands either for Primary Wave
P-Waves has the highest velocity and is therefore the
first to be recorded
It is a longitudinal wave and motion is parallel to
direction of propagation
P-Waves
18. Like P-Waves they are high frequency, short-wavelength
waves
But instead of being longitudinal they are transverse
On the surface of the Earth, S-Waves are responsible for
the sideways displacement
S-waves move like waves in a rope
S-Waves
19. Travel near the surface
Surface Waves are of following types
Rayleigh Waves
Love Waves
The combination of Rayleigh and Love Waves results in
ground heave and swaying buildings
Surface waves cause the most devastating damage to
buildings, bridges, and highways
Surface Waves
20. These instruments are used to measure the magnitude of
the Earthquake
The seismograph consists of a seismometer (the
detector) and a recording device
Richter Scale was developed by Charles F.Richter in
1935
It measures the magnitude of the earthquakes
Seismograph & Richter Scale
21. 90 percent of the world's earthquakes occur along plate
boundaries
47% of major earthquakes occur within 100 miles of a
convergent plate boundary
71% of major earthquakes occur within 200 miles of a
convergent plate boundary
Distribution of Earthquakes