EARTHQUAKES!
• Focus
• Epicenter
• Point at which the
earthquake
originates
• Point on earth’s
surface above the
focus
WHAT IS AN EARTHQUAKE?
• Earthquake
• Where do earthquakes
occur?
• The shaking of Earth’s
crust due to the release
of built-up pressure
and stress
• Usually at plate
boundaries but also at
small faults
Earthquakes Waves
• P waves
• S waves
• Primary; compressional;
travel through solid,
liquid and gas; FASTEST!
• Secondary; shear; only
travel through solids; 2nd
fastest
• L waves
• Surface waves; very slow
Measuring Earthquakes
• Seismograph
• Seismometer
• Record sheet that
the seismometer
produces
• Measures
earthquake waves
Locating Earthquakes Epicenters
• Need information
from at least 3
seismograph
stations
Strength of Earthquakes
• Magnitude
• Richter Scale
• Strength of the
Earthquakes
• Measure the
magnitude of
earthquakes……r
anges from 1-10
Earthquake Hazards
• Liquid
• Liquefaction
characteristics
• Aftershocks
• tsunamis
• Tremors after the
main earthquake
has passed; just as
dangerous!
• Undersea
earthquakes that
spark large, rogue
waves
The Shadow Zone
• Shadow Zone
• Moho
• Area that receives no
earthquake waves do
to Earth’s liquid layer
(outer core)
• Bending of
Earthquakes waves
and they slow when
they pass through the
liquid astehenosphere