What is an Earthquake? Video Lecture | Science Class 8

what is an earthquake
an earthquake takes place when two
blocks of the earth suddenly slip past
one another the surface where the slip
is called a fault place the location we
below the Earth's surface where the
earthquake starts is called the
hypocenter and the location directly
above it on the surface of the earth is
called the epicenter sometimes an
earthquake has four shocks these are
smaller earthquakes that happen in the
same place before a large earthquake
takes place the largest main earthquake
is called the main shock made shocks are
always followed by aftershocks that
occur in the same place and can continue
for weeks months and even years
what causes earthquakes and where do
they happen the earth has four major
layers the inner core outer core mantle
and crust the crust and the top of the
mantle make up a thin skin on the
surface of our planet but this skin is
not all in one piece it is made up of
many pieces covering the surface of the
earth
these pieces are called tectonic plates
and the edges of the plates are called
the plate boundaries these pieces keep
moving around slowly sliding past one
another and bumping into each other
these plate boundaries are made up of
many faults and most earthquakes around
the world occur on these faults
why does the earth shake when there is
an earthquake while the edges of the
Falls are stuck together and the rest of
the block is moving the energy that
would normally cause the blocks to slide
past one another is being accumulated
when the force of the moving blocks
finally overcomes the friction of the
jagged edges of the fault it breaks free
and all that stored of energy is
released the seismic waves shake the
earth as they move through it and when
the waves reach the Earth's surface they
shake the ground and anything on it like
a houses and us the energy radiates
outward from the faults in all
directions in the form of seismic waves
like ripples in a pond
how are earthquakes recorded earthquakes
are recorded by instruments called
seismic rocks the recording they make is
called a seismograph the seismograph has
a base that sets formally on the ground
and a heavy weight that hangs free when
an earthquake causes the ground to shake
the base of the seismogram shakes too
but the hanging weight does not instead
the spring that is hanging absorbs all
the movement the difference in position
between the shape and part of the
seismograph and
this part is what is recorded