Earthquakes are caused by the release of stored energy in the earth's interior. The point of origin is called the focus, and the point directly above on the surface is the epicenter. Energy from the focus propagates as seismic waves that cause tremors and destruction. The Richter scale is used to measure an earthquake's magnitude based on the intensity of shaking and damage. Primary and secondary body waves travel through the earth's interior at different speeds depending on the material's density, while surface waves cause surface destruction as they travel along the earth's surface.

3. Anilkumar S.S
Register No: 13983004
Social Science Option
KUCTE Nedumangadu

5. • The processes that take
place in the interior of the
earth causes in the storage
of energy in some portions
in the earth. Earthquakes
occur on those instances
when these energy is being
released. The point of origin
of the earthquakes is known
as focus and the point just
above the focus on the
surface of the earth is
known as epicenter.

7. The energy being
released from the
focus propagates as
waves. These cause
tremors on the
surface of the earth
and cause
destruction.
• The instrument used to
measure to magnitude of
the earthquake is called a
seismograph. The
intensity of the
earthquake is measured
based on the Richer
Scale

9. Richer Scale Effects
1 - 3 We don`t feel the tremors. But recorded in the seismograph
3 - 4 T remors felt
4 - 5 Small objects fall, doors and windows shake.
5 - 6 Damage to weak buildings
6 - 7 There is strong tremor over vast areas, weak buildings
collapse.
7 - 8 Comparatively strong earthquake, there is a lot of destruction
over large areas, strong buildings collapse, tsunamis caused.
8 - 9 Severe earthquake, causes destruction in more than 100
kilometre circumference, cause strong tsunamis (like the
2004 tsunami in the Indian Ocean)
9 and above Very intense earthquake, very rare.

10. Primary waves move very fast through solids, and very slowly
through liquids. These waves reach the epicenter from the focus
first. But secondary waves move only through solids. They do
not travel through liquids. These reach the epicenter following the
primary waves. These two waves travel to interior of the earth .
So they are known as body waves. Depending on the density of
the material they pass through, there is a difference in their speed.
Waves the material traversed is more dense, the speed is more and
where the density less, the speed is also less,. According to the
density, the direction of the waves change . Surface waves reach
the epicenter last. They through the surface of the earth and cause
destruction on the earth`s surface.