Transcript Hazard Committee

Earthquakes
Presented you to by the
Hazard Committee
Madeline Galac
Nicole Barstrom
Where Do Earthquakes Occur?
• Earthquakes
normally
occur on plate
boundaries.
Types of Plate Boundaries
• Spreading Zone
- This is an area where two plates are moving apart from one
another
- One example is the Mid-Atlantic Ridge
• Transform Fault
- This is where two plates are sliding past each other
- One example is the San Andreas Fault on the coast of
California and Northwestern Mexico
• Subduction Zone
- This is where one plate moves on top of another causing one to
be subducted into the mantle where it melts.
- One example is the Western Coast of South America near Chile.
Earthquakes: Strong vs. Weak
Strong Earthquakes:
 Occur deeper in the
crust
 Are associated with
Subduction Zones
 Do not produce
Surface Waves




Weak Earthquakes:
Occur closer to the surface
of the Earth
Are associated with
Transform Faults and
Spreading Zones
Are also associated with
quakes not related to plate
tectonics
Produce surface waves
Direct Effects of Earthquakes
• Ground shaking
• Disruption of Utilities
• Damage to personal
items and buildings
• Water table adjustment
• Aftershocks
Indirect Effects of Earthquakes
• Ground failures
• Landslides
• Subsidence (drop in
elevation of land due to
removal of water)
• Liquefaction (reduction in
the strength of saturated
soils)
• Tsunamis (tidal waves)
• Flooding
• Seiches (movement of
inland bodies of water)
• Fires from electrical
difficulties
Earthquake Prediction
Although it is likely to predict where an
earthquake may occur, it is virtually
impossible to predict when and of what
magnitude.
However, there are some signs that some
scientists believe characterize earthquake
events as was seen in the Haicheng
Earthquake in 1975.
Possible Signs of an Earthquake
Changes in land
elevation and ground
water levels
Peculiar animal
behavior
Regional increase of
seismicity
(foreshocks)
Stick Slip Experiment
• This experiment showed
that earthquakes are nearly
impossible to predict as
far as specific details are
concerned.
• It showed, though, that if
an area that is prone to
seismic activity has
received a few small
quakes in the recent past
without a big event, that
there should be a big
quake in the near future.