measurement of earthquakes

Do Now
Seismic Waves cary, the energy off and
earthquake from the focus. Through
earth’s Interior and across the surface.
Seismic Waves
Seismic waves carry the energy of an earthquake
P waves
compress and
expand the
P waves move
the fastest!
S waves vibrate
from side to side
as well as up and
S-waves move at
about ½ the speed
of P waves!
Surface waves
produce the most
severe ground
movements &
damage even
though they move
the slowest!.
How is the Size of Earthquakes
• A seismograph is the the tool used to
measure the strength of an earthquakes
How is the Size of Earthquakes
• The seismograph prints out a seismogram
that scientists read to determine the
strength of the quake.
How is the Size of Earthquakes
• The data from the seismogram is
translated into a 1-10 rating. Each step in
the scale represents a tenfold increase in
the size of the quake!
How are Earthquakes Measured?
• Earthquakes are measured based on
three different scales.
• The first measures the actual size of the
• The second measures the effects or
damage of the quake.
• The third measures the total energy of the
Mercalli Scale
• Developed in early twentieth century
• Measures the strength of ground motion
• It is not precise as the ground motion can
cause different amount of damage at
different locations
Richter Scale
• Developed in 1930s
• Gives the rating of the size of seismic
• Provides accurate movement for small,
nearby earthquakes
• Does not work well for large or distant
Moment Magnitude Scale
• Used today, as it is the most precise
• Used to rate earthquakes of all sizes, near
or far