Transcript ES 6-2 Notes

Chapter 6 Earthquakes
1) What Causes earthquakes?
2) What scales are used to measure
earthquakes?
3) How do we find the epicenter of an
earthquake?
4) How do geologists monitor faults?
What causes Earthquakes?
• An earthquake is the
shaking and trembling
of rock beneath
Earth’s surface.
Earthquakes are caused by…
• Plate movement causes
stress to build up in the
crust until the rock
breaks causing an
earthquake.
Focus vs. Epicenter
• The focus is the
area beneath
Earth’s surface
where rock that is
under stress
breaks.
• The epicenter is
the point on the
surface directly
above the focus.
Seismic Waves
• Seismic Waves
carry the energy
from an
earthquake away
from the focus
and across the
surface..
Types of Seismic Waves
• There are three
main types of
seismic waves.
• P-waves
• S-waves
• Surface Waves
P-Waves
• P-Waves or
Primary waves,
are the fastest
waves and move
by compressing
the ground like an
accordion.
S-Waves
• Also known as
Secondary Waves.
• Not as fast as
primary waves and
cannot move
through liquid.
• Move side to side
and back and forth.
Surface Waves
• Slowest and most
destructive
waves.
• Form when Pwaves or SWaves reach the
surface.
• Move like waves
on the ocean.
Seismograph
• An instrument
that measures
and records
seismic waves
How we measure Earthquakes.
• Earthquakes give
off seismic waves
(vibrations that
carry the energy
from an earthquake
through the earth
and across the
surface).
The scales we use are:
• Richter Scale
• This scale measures
the size of an
earthquake based
on the size of the
seismic waves as
measured on a
seismograph.
Which earthquake is bigger?
The scales we use:
• Mercalli Scale:
• The Mercalli scale
rates earthquakes
based on the level
of damage they
cause.
• Rank from 1 least
damage to 12, total
destruction.
What would you rate this
earthquake?
What would you rate this
earthquake?
The Moment Magnitude Scale
• The moment magnitude
scale estimates the
total energy released by
an Earthquake.
• This is done by looking
at seismographs as well
as movement along the
fault
Finding the Epicenter
Finding the epicenter
Finding the Epicenter