Transcript earthquakes - SchoolRack

Bell Ringer
Monday 11/30/09
Where do most volcanoes tend
to form?
a. convergent plate boundaries
b. divergent plate boundaries
c. hot spots
d. all of the above
EARTHQUAKES
• Earthquakes – vibrations
of the Earth’s crust
• Elastic Rebound Theory –
theory that rocks that are
strained past a certain point
will fracture and spring back
to their original shape
• Seismic Waves – energy
released as vibrations when
rocks fracture; these
vibrations travel through the
Earth
• Aftershocks – a tremor
that follows and is smaller
than a major earthquake
• Focus – the area along a fault
where slippage first occurs
(see Figure 2-p 739- copy it
into your notes)
• Epicenter – the point on
Earth’s surface directly
above the focus
• Earthquakes that cause the most
damage usually have a shallow
focus (a depth in the Earth of
less than 70 km)
• Earthquakes with a deep focus
cause less damage because much
of their energy has been used up
before the seismic wave reaches
the surface
• 3 Major Earthquake
Zones
• Pacific Ring of Fire
• Mid-ocean ridges
• Eurasian-Melanesian
belt
• Fault Zone – group of
interconnected faults
(example – San Andreas
Fault in CA)
• Seismograph – instrument used to
detect seismic waves
• 3 types of waves
• P waves – primary waves
•Fastest waves
•Move through solid and liquid
material
• S waves – secondary waves
•Move through solid material only
• L waves – long waves
•Slowest waves
•Also called surface waves
•Occur when P waves and
S waves reach the surface
•Destructive to Earth’s
surface
• Locating the epicenter of an
Earthquake
• Use a time-distance graph to
plot arrival times of P waves,
S waves and L waves
• Need three locations to
determine the epicenter of
earthquake
• Richter scale – used to
express the magnitude of an
earthquake
• Magnitude – is a measure of
the energy released by an
earthquake
• Largest recorded earthquake
measured 9.6 on the Richter
scale
• Microquakes – have
magnitudes of less than 2.5
on the Richter scale
• Earthquake Dangers
• Building collapse
• Landslides
• Fires
• Falling objects
• Flying glass
• Explosions from broken gas and
electric lines
• Flooding from broken dams
• To withstand an earthquake,
buildings should:
• Have strong walls
• Be built on soil or rock that
is firm
• Tsunami – a giant ocean wave
caused by an earthquake with an
epicenter on the ocean floor
• An earthquake may also trigger
underwater landslides – which
may cause a series of tsunamis
• Earthquake safety
• Before an earthquake, be prepared
•make a plan
•have emergency supplies
–Canned food & bottled water
–Flashlight, portable radio, &
batteries
•Learn how to turn off the gas,
water, and electricity in your
home.
• During an earthquake, stay calm
• Get under a desk or table or stand
in a doorway
• Stay away from windows and
heavy furniture
• If in a car, stop in a place away
from tall buildings, tunnels,
power lines, and bridges; stay in
the car until the tremors stop
• After an earthquake, be cautious
• Check for fire and fire hazards
• Wear shoes when walking in
broken glass
• Avoid downed powerlines and
objects touched by downed wires
• Earthquake warnings & predictions
• Strange animal behavior
• Seismic gaps – a place where the
fault is locked and unable to move;
likely place for future earthquake
• Scientists detect:
•Slight ground tilting
•A decrease in local P waves
Giant Earthquake Hits Shelby
County!!
• Write a brief newspaper article
detailing the events that occurred
before, during, and after an
earthquake. Be as creative as you can
be. However, your article must
include a picture and the scientific
words that we have been studying in
class.