eathquack causes

1. Topic :EARTH QUAKE
Submitted to : Mr zeeshan
Submitted by : alina Arshad
Roll no : 13

2. Earth quake
• Also known as QUAKE or TREMOR or TEMBLOR

3. EARTHQUAKE

4. Terminologies
Focus or Hypocenter:
Point from where energy is first released
Epicenter:
Point on ground directly above the focus is known as
Epicenter.

5. Classification of earthquakes on the basis of depth of focus:
Shallow focus Earthquake: If Focus Depth = 0 -70 Km.
Intermediate focus Earthquake: If Focus Depth = 70 -300 Km.
Deep focus Earthquake: If Focus Depth = 300 -700 Km.

6. Genetic classification of earthquakes
Causes of earthquakes
Types of earthquakes

7. Types of earthquakes
1 ……..Tectonic Earthquakes
2 .…….Non Tectonic Earthquakes
i ………Volcanic Earthquakes
ii ………Impact Earthquakes

8. Tectonic Earthquakes
Includes all earthquakes resulting from deformation of rocks during mountain
building.
Majority of earthquakes are of tectonic earthquakes because these results due
to flow of accumulated energy (over long period of time).
These are important
Scientifically---- to study the internal structure of the Earth
Socially----------- due to their tremendous effects on human beings.
Tectonic Earthquakes are caused by
!.............. Elastic Rebound
!.............. Sudden shearing during Plastic flow
!.............. Folding

10.
Elastic Rebound
The Earthquake cycle progress from a
fault i.e. not under stresses.
Stresses develop due to plate tectonic
movement. As stresses accumulate in
rocks in both sides of fault the rock is
pressed tightly, together and slowly
distorted until its elastic limit is reached.
Then rock is rupture suddenly and
released its stored up energy as it snaps
back into position approximately its
unstrained conditions.

12. •Folding:
When folding takes place, the sudden tensional cracking and
crushing results, due to which stored up energy releases, in the
form of waves. Since such cracks are usually small, i.e. why the
earthquake caused is minor in size.

13. •Sudden Shearing during plastic flow:
Only lithosphere has the strength and the brittle behavior to
fracture in an Earthquake.
Deep within the earth rocks are thought to be plastic. When
elastic limit is exceeded rocks do not always break, rather
they flow. Non elastic movement in which rocks do not part
(faulted) is called plastic flow.
So during plastic flow rocks may take on a permanent
change of shape in addition to its elastic deformation without
parting anywhere, releasing stored up energy in the form of
waves.

15. •Non Tectonic Earthquakes
•Volcanic Earthquakes
It has long been known that Earthquakes are accompanied the
eruption of volcanoes. The movement of magma and gases
within earth especially the spasmodic movement is another
means of shocks.
Shocks may occur before volcanic activity.
A greater number of shocks follow an eruption due to
readjustment within magma and surrounding rocks.
Shocks due to volcanic activity are less sever and destructive
and are upto magnitude of 6.

16. During volcanic activity the shocks can be caused in various ways,
e.g.
•High pressure eruption from a smaller vent.
•Falling of volcanic lava on earth
•Stopping of flow of magma during activity.
•Stoping in magma chamber.
•Crystallization in magma.
•Tensional cracking during cooling of lava.

17. •Impact Earthquakes
This cause of earthquake is on the surface of the earth and is not
due to any inside reason. Earthquakes are lesser in size but some
times are of medium sized. Rare these are lager in size, however
depends upon the size of impacting material.

18. Impact earthquakes are caused in different ways:
•Surface Explosion up to magnitude 5.
•Meteorite Falling smaller magnitude sometimes medium sized.
•Cave ins
•Land slides