Earthquakes!
Earthquake
 describes
both sudden slip on a fault, and
the resulting ground shaking and radiated
seismic energy caused by the slip.
Seismogram
showing
Shaking from an
Earthquake.
Earthquakes happen at Plate
Boundaries and Faults
Focus vs. Epicenter


Focus: The location
where the
earthquake begins.
At fault line
underground.
Epicenter: The point
on the Earth's surface
located directly
above the focus of
an earthquake
Earthquake Sequence
 Foreshock:
Small shaking before major
shaking.
 Earthquake: Primary Wave, Secondary
Wave (also Surface waves such as
Rayleigh and Love Waves: cause the
most damage).
 Aftershocks: Smaller shaking after main
quake.
Primary Wave (PWave/Compressional Wave)




Primary Wave (Pwave): Fastest wave.
First to arrive and be
felt.
Waves are parallel to
direction of
movement.
Feels like an
explosion.
Move through solids,
liquids, gasses.
Secondary Wave (S-Wave)



S-Wave: Slower than
P-Wave. Arrives and
felt second.
Wave are
perpendicular to
direction of
movement. (Shear).
Can only move
through solids.
Seismograms: Shows P and S
Waves
Which is P-Wave? Which is S-Wave?
P-Wave and S-Wave shadow
Zones
Moho: Boundary
Between crust and
Mantle.
Finding the Epicenter: Triangulate
Position with at least 3
Seismometers
Richter Scale




Used to measure
earthquakes.
Logarithmic Scale.
Each whole number
is 10 times more
intense.
Ex. A Magnitude 3 is
100 times more
intense than
Magnitude 1.
 Occurs
when thrust fault under ocean
displaces ocean water upward.
Tsunami
Liquefaction
Loosely packed,
water logged sediments
can act like a fluid from
intense shaking during
an earthquake.
Earthquake Damage: Haiti
2010
Earthquake Safe Structures