Earthquake
the shaking of
the Earth's
crust caused
by a sudden
release of
energy.
Elastic rebound theory
Strain in the rocks cause the
rocks to bend and stretch like a
rubber bands. When the strain
becomes too great the rocks
break and spring back
(rebound). As the rocks snap
back into position, they release
energy in the form of seismic
waves.
Elastic Rebound Theory
Epicenter vs Focus
Focus - the actual point
along the fault where
slippage occurs
Epicenter - is the location
on the earth's surface
directly above the focus.
Earthquake Waves
I. Body Waves - travel
through the body of the
earth.
II. Surface Waves
(L - waves)- Travel through
the surface of the earth
Body Waves
P - waves - primary or
compressional waves
S- waves - secondary or
shear waves
P - waves
A. Back and forth wave motion
alternately squeezes and
stretches.
B. They can travel through
any material ( solid rocks,
magma, ocean water, even
air).
S- waves
A. Side to side wave motion at
right angles to the direction
the wave is traveling
B. They can travel through
solids but not through
liquids.
Surface Waves
1. Produce when the P and
S - waves reach the
surface
2. Slow and rolling waves
Measuring and
detecting earthquakes
Seismographs - instrument
that detects and records
earthquake (seismic)
waves
Seismographs
A. Horizontal Motion
B. Vertical Motion
C. Heavy weight is attached to
a base anchored in bedrock
D. Seismogram - record
sheets on drums that move
very slowly 3287
Earthquake Magnitude
Magnitude - the strength, or
magnitude of the energy
produced by the earthquake
Earthquake Magnitude
Richter Scale - magnitude
number represents the
amount of energy release by
the earthquake itself.
Each number is 32 times
stronger than the one before
it.
Richter Scale
Magnitudes Effects
Less than 3.5 *Generally not felt, but
recorded.
3.5-5.4 *Often felt, but only minor
damage.
5.5-6.0 *Slight damage to
buildings.
Richter Scale
Magnitudes Effects
6.1-6.9 * Can be destructive in
areas where people live.
7.0-7.9 *Major earthquake.
Causes serious damage.
Richter Scale
Magnitudes Effects
8 or greater *Great earthquake.
Total destruction to
nearby communities.
Richter TNT Energy
Example
Magnitude Equivalent (approximate)
3.5 1,000 pounds
Large Quarry or Mine Blast
4.0 6 tons
4.5 32 tons
Average Tornado
5.0 199 tons
Richter TNT Energy
Example
5.5 500 tons
Little Skull Mtn., NV Quake, 1992
6.0 6,270 tons
Double Spring Flat, NV Quake, 1994
6.5 31,550 tons
Northridge, CA Quake, 1994
7.0 199,000 tons
Hyogo-Ken Nanbu, Japan Quake,
Richter TNT Energy
Example
7.5 1,000,000 tons
Landers, CA Quake, 1992
8.0 6,270,000 tons
San Francisco, CA Quake, 1906
8.5 31,550,000 tons
Anchorage, AK Quake, 1964
Richter TNT Energy
Example
9.0 199,999,000 tons
Chilean Quake, 1960
10.0 6.3 billion tons
(San-Andreas type fault circling Earth)
12.0 1 trillion tons
(Fault Earth in half through center,
OR Earth's daily receipt of solar
energy)
Earthquake Magnitude
Rossi- Forel Scale - Based
on description of what
happens during the
earthquake
Many things influence the
amount of damage done
by an earthquake.
Earthquake Magnitude
Seismic moment - a more
accurate method of
measuring total energy
involved.
Earthquake Magnitude
Modified Mercalli Intensity Scale
I. People do not feel any Earth movement.
II. A few people might notice movement if
they are at rest and/or on the upper
floors of tall buildings.
Modified Mercalli Intensity Scale
III. Many people indoors feel movement.
Hanging objects swing back and forth.
People outdoors might not realize that an
earthquake is occurring.
Modified Mercalli Intensity Scale
IV. Most people indoors feel movement.
Hanging objects swing. Dishes, windows,
and doors rattle. The earthquake feels
like a heavy truck hitting the walls. A few
people outdoors may feel movement.
Parked cars rock.
Modified Mercalli Intensity Scale
IV. Most people indoors feel movement.
Hanging objects swing. Dishes, windows,
and doors rattle. The earthquake feels
like a heavy truck hitting the walls. A few
people outdoors may feel movement.
Parked cars rock.
Modified Mercalli Intensity Scale
V. Almost everyone feels movement.
Sleeping people are awakened. Doors
swing open or close. Dishes are broken.
Pictures on the wall move. Small objects
move or are turned over. Trees might
shake. Liquids might spill out of open
containers.
Modified Mercalli Intensity Scale
VI. Everyone feels movement. People have
trouble walking. Objects fall from
shelves. Pictures fall off walls. Furniture
moves. Plaster in walls might crack.
Trees and bushes shake. Damage is slight
in poorly built buildings. No structural
damage.
Modified Mercalli Intensity Scale
VII. People have difficulty standing.
Drivers feel their cars shaking. Some
furniture breaks. Loose bricks fall from
buildings. Damage is slight to moderate
in well-built buildings; considerable in
poorly built buildings.
Modified Mercalli Intensity Scale
VIII. Drivers have trouble steering. Houses
that are not bolted down might shift on
their foundations. Tall structures such as
towers and chimneys might twist and fall.
Well-built buildings suffer slight damage.
Poorly built structures suffer severe
damage. Tree branches break. Hillsides
might crack if the ground is wet. Water
levels in wells might change.
Modified Mercalli Intensity Scale
IX. Well-built buildings suffer considerable
damage. Houses that are not bolted down
move off their foundations. Some
underground pipes are broken. The
ground cracks. Reservoirs suffer serious
damage.
Modified Mercalli Intensity Scale
X. Most buildings and their foundations
are destroyed. Some bridges are
destroyed. Dams are seriously damaged.
Large landslides occur. Water is thrown
on the banks of canals, rivers, lakes. The
ground cracks in large areas. Railroad
tracks are bent slightly.
Modified Mercalli Intensity Scale
XI. Most buildings collapse. Some bridges
are destroyed. Large cracks appear in the
ground. Underground pipelines are
destroyed. Railroad tracks are badly
bent.
Modified Mercalli Intensity Scale
XII. Almost everything is destroyed.
Objects are thrown into the air. The
ground moves in waves or ripples. Large
amounts of rock may move.
Finding the Epicenter
1. Must have three
seismograms from three
different stations.
2. Determine the lag time
between
s-wave and p-wave.(s-p
3304
interval)
Finding the Epicenter
3. Using time travel graphs
determine the distance
the seismogram is away
from the epicenter.
Finding the Epicenter
4. Three circles are drawn on
the map at a radius
determine by distance of
epicenter.
5. Where three circles meet is
the location of earthquake.
Earthquake Prediction
I. Earthquakes occur as periodic
events
II. Microquakes
III. Electrical resistance
IV. Amount of radioactive
radon in well water.
Earthquake Prediction
V.Seismic gap method-
mapping the focus of
earthquakes and finding where
the plates have not moved. This
location is the location where
the next big earthquake may
come from.
Earthquake Preparedness
Before the quake
1. Decide where the
family will meet.
2. Learn how to shut
of gas, electric and
water
Earthquake Preparedness
3. Have extra
cash, food and
water prepare
for diasters
Earthquake Preparedness
During Quake
Duck and
Cover
Under heavy
furniture or
door frame.
Earthquake Preparedness
After quake
1. Check for gas and water leaks
2. Check building for cracks
3. Check food and water
supplies
Earthquake Preparedness
4. BE PREPARE FOR
AFTERSHOCKS!!!!!!!!!!
3322-3342
Afro-American Scientist
June Bacon-Bercey
In1979 she became Chief Administrator
of television activities for National
Organization of Atmospheric Agency
(NOAA). June Bacon - Bercey of Silver
Spring, Maryland who is a scientist, an
international expert on weather and
aviation, a wife and a mother.