Download Answer the following: Answer the following: Draw a

Answer the following:
Answer the following:
Draw a diagram that indicates the fault line, focus, seismic waves and
epicenter of an earthquake.
Draw a diagram that indicates the fault line, focus, seismic waves and
epicenter of an earthquake.
What are the three major earthquake zones?
What are the three major earthquake zones?
Name the three types of seismic waves and put them in order from
fastest to slowest.
Name the three types of seismic waves and put them in order from
fastest to slowest.
What are two methods for measuring an earthquake?
What are two methods for measuring an earthquake?
What is a tsunami? How does it occur?
What is a tsunami? How does it occur?
Name two things you should do under the heading “Earthquake
Safety”
Name two things you should do under the heading “Earthquake
Safety”
What research are the Chinese doing in relation to earthquake
prediction?
What research are the Chinese doing in relation to earthquake
prediction?
Earthquakes are defined as vibrations in
the Earth’s crust (lithospheric plates)
Elastic Rebound Theory:
rocks on each side of a fault are moving slowly. If the fault is locked, stress in the
rock increases. When a rock is stressed past a certain point, the rocks fracture,
separate at their weakest point, and then spring back to their original position.
Rocks along a fault release
energy in the form of vibration
called seismic waves
Aftershocks are a series of smaller
tremors which occur when the
surrounding rocks become stressed,
fracture, and then spring back
The area along a fault where slippage first occurs is called the focus
The surface of the earth directly above the focus is called the epicenter
When an earthquake occurs, seismic waves radiate outward in all directions, similar to
a rock dropped in water
Earthquakes can be at three depths:
Most earthquakes do not originate deep in the earth, because rocks act like plastic and
bend rather than fracture.
The Earth has THREE major earthquake zones:
At some plate boundaries there are groups of interconnected faults called fault zones.
Earthquakes do not ONLY occur at
plate boundaries…
This is due to deep fault zones created
long ago.
The San Andres Fault is
one of these fault zones.
Recording Earthquakes
Seismic waves can be detected and
recorded by using an instrument called
a seismograph
A seismograph records motion by tracing waveshaped lines on paper or by translating the
motion into electronic signals.
There are three types of seismic waves:
Primary waves
Move fast
Moves through solids and liquids
First to be recorded on
seismograph
Secondary waves
Move slow
Moves through solids only
Second to be recorded on
seismograph
When P and S waves reach the earth’s surface their energy is converted into slow
moving waves that travel across the surface
To locate an earthquake scientists analyze the difference between arrival times of the P
and S waves using the seismograph.
Primary waves travel 1.7 times faster than S waves.
The more time that passes between the P and S wave arrival, the further away the
earthquake is from the seismograph
Scientists can use a graph to calculate how far away the earthquake was.
Using the data from three separate seismograph stations
scientists can determine the epicenter of the earthquake.
Small Scale Investigation, page 105
Earthquake Measurement: two methods
Scientist use the Richter Scale to determine how
strong an earthquake is (MAGNITUDE)
Richter Earthquake Magnitudes Effects
Less than 3.5 Generally not felt, but recorded.
3.5-5.4 Often felt, but rarely causes damage.
Under 6.0 At most slight damage to well-designed
buildings. Can cause major damage to poorly
constructed buildings over small regions.
6.1-6.9 Can be destructive in areas up to about 100
kilometers across where people live.
7.0-7.9 Major earthquake. Can cause serious
damage over larger areas.
8 or greater Great earthquake. Can cause serious
damage in areas several hundred kilometers
across.
The Mercalli Scale
expresses the intensity
(or the amount of
damage) an
earthquake causes
Earthquake Damage
Most injuries from earthquakes are caused by the collapse of buildings/structures, falling
objects, landslides, fires, explosions, and flooding
Very few buildings and structures can withstand the ground vibrations caused by
earthquakes
Earthquake Damage
A major earthquake with an epicenter on the ocean floor is called a tsunami
A major drop or movement in the ocean floor causes the ocean water to move violently,
eventually this movement results in huge waves that crash into land formations
Earthquake Safety: a few basic rules
Before an earthquake occurs, be prepared
During an earthquake, stay calm
After an earthquake, be cautious
Earthquake Warnings and Predictions
One of the earliest means of predicting earthquakes was by observing animal behavior
Just before an earthquake animals appear nervous and restless
Chinese researchers are still investigating this phenomena
Earthquake Warnings and Predictions
Scientist have placed various instruments along known fault lines to record small
movements in the ground
Along some faults scientist have found places of immobile rock called seismic gaps
A lot of stress builds up at these sites and seismic gap areas are considered earthquake
hot spots
Earthquake Warnings and Predictions
Scientists can also detect a slight titling of the ground just before an earthquake
Scientist record cracks and strains in rocks as well as the magnetic and electrical
properties
All of these rock properties change slightly before an earthquake
There is no good way to predict an earthquake