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EARTHQUAKES!
Part 3
Quick review:
Where do most earthquakes occur?
90% happen on the ring of Fire
Which plate does the ring surround?
The Pacific Plate
Where did the four that we studied occur?
Chile, California, Alaska and Japan
Which was the largest of all time?
Valdivia – 1960
How big was it?
9.2 to 9.6 on the Richter Scale
What two things did the Valdivia quake cause?
Tsunamis up to 82 feet tall
And
It caused volcano to blow!
How do we measure earthquakes?
We use the Richter magnitude scales
and the Mercalli intensity scale.
What is the difference?
The Richter scale measures how much
energy is released in an earthquake
The Mercalli intensity scale measures
how much damage was done
Scientists use the Richter scale to compare earthquakes
while studying plate tectonics
Insurance companies use the Mercalli scale to help them
decide how much your damaged house is worth.
What is the scale for the Richter scale?
1-10 - each number is 10x larger than the last
What is the scale for the Mercalli scale?
1-12 and is measured by the damage done
Can a quake have more than one number?
On the Richter scale – no
On the Mercalli scale – yes – it depends upon
where you are.
What is a focus?
It is the exact spot where an earthquake
occurred – usually deep below ground
What is the epicenter?
It is the spot directly above the focus – on land
How big was it?
9.2 to 9.6 on the Richter Scale
What two things did the Valdivia quake cause?
Tsunamis up to 82 feet tall
And
It caused volcano to blow!
The focus of an earthquake the actual
spot where the quake started
it is usually deep under ground
When the plates
get stuck they
build up pressure
until one of them
snaps.
The exact spot
that the rock
snapped is the
focus.
The spot on the
ground above the
focus is called
the epicenter.
The shaking that
we feel is called a
seismic wave.
Seismic waves
travel through
earth.
So what
exactly is
a seismic
wave?
Seismic
Seismic waves
waves are
are
energy
energy that travels
on
on waves
waves like
like sound
sound
and
and light.
There are two different types
of seismic waves:
Body waves travel through the interior of
the earth. The two types of body waves
are P-waves and S-waves
Surface waves – these travel through the
rock that we are standing on – the crust
P-Waves
(primary waves)
P-waves can travel through
anything including liquid!
They are almost twice as fast as
any other wave.
P-waves travel in a push motion
S-Waves
(secondary waves)
S-waves can only travel through
solid objects – like earth’s crust
and core.
They move in a snakelike motion
Surface waves
Surface waves move in both directions at once!
They are responsible for most of the damage
that earthquakes do – mostly because the
surface waves run through the rock that we
build on top of.