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67 Cards in this Set

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  • Back
Seismic waves that travel through the Earth's interior:
Body waves
What happens as the seismic waves spread out away from the focus?
The vibrations start to get smaller and smaller.
A fracture along which movement occurs:
The amplitude or heigth of the largest seismic wave in an earthquake:
Where is the epicenter located?
Directly above the focus
What are the 2 types of body waves?
1) Primary (P) waves
2) Secondary (S) waves
What percent of earthquakes are shallow focus earthquakes?
Where are the most intense vibrations generated?
At the focus
Seismic waves that travel along Earth's surface:
Surface waves
A vibration of the Earth:
What do you need to locate an earthquake's epicenter?
At least 3 seismographs
The effect an earthquake has on people and property:
What was the magnitude of the 1989 World Series earthquake?
7.1 on the Richter Scale
How deep are shallow focus earthquakes?
0-100 kilometers deep
Point where the earthquake originates; where the actual break occurs:
Compressional waves that expand and contract and vibrate w/ a push-pull motion:
Primary (P) waves
What type of seismic waves are needed to locate an earthquake's epicenter?
Only body waves:
1) primary (P) waves
2) secondary (S) waves
What is used to measure an earthquake's intensity?
The Modified Mercalli Scale (Roman numerals I.- VII.)
What percentage of earthquakes are intermediate focus earthquakes?
The movement or vibrations that are produced as stress is released along a fault:
Seismic waves
A seismic sea wave caused by displacement of the ocean floor:
What are the 2 types of surface waves?
1) Rayleigh (R) waves
2) Love (L) waves
Instrument that records seismic waves:
Where will the maximum amount of damage and fatalities in an earthquake occur?
At the epicenter
The boundary between the North American and Pacific plates:
The San Andreas Fault
At what depths do deep focus earthquakes occur?
350+ kilometers
Waves that vibrate perpendicular to the direction of travel:
Secondary (S) waves
What is used to measure an earthquake's magnitude?
The Richter Scale (logarithmic scale)
"Ground zero" zone:
What type of seismic waves cause the most property damage during an earthquake?
Surface waves
Point on the Earth's surface that lies directly above the focus:
How deep are intermediate focus earthquakes?
100-350 kilometers
What type of foundation or ground is most stable during an earthquake?
Approximately how much more energy is released in a 6.5 Richter magnitude earthquake than in one with a magnitude 5.5?
30 times
The "snapping back" of rock to its near-original shape after an earthquake:
Elastic rebound theory
What percentage of earthquakes are deep focus earthquakes?
Of the seismic waves produced by an earthquake, which type travels fastest and has the highest velocity?
An earthquake’s source of energy is located at the _____________, but the location at the land surface above that point is called the ______________.
focus, epicenter
What is the most dangerous type of surface waves?
Love (L) waves
Where do most earthquakes occur?
At plate boundaries
Which seismic wave will reach seismographs first?
P waves
Effect of earthquake that occurs if there is wet, sandy ground; when the ground starts to shake, the sand grains lose contact w/ eachother and lose their stability:
Going up one whole unit on the Richter scale represents how much of an increase?
10-fold increase in AMPLITUDE

30-fold increase in ENERGY
The distance to an earthquake epicenter is determined by measuring what?
The time delay between the arrival of P and S waves.
Seismic waves that produce circular, rolling movements; similar to water waves:
Rayleigh (R) waves
What earthquake magnitude is needed to cause a tsunami?
Magnitude 8+ earthquake
What is the current rate of drifting for the San Andreas Fault?
2 inches per year
What is the smallest earthquake magnitude that can be felt by humans?
Magnitude of 2
What were the largest historical earthquakes to ever occur along the San Andreas Fault?
San Francisco earthquakes of 1857 and 1906
Studies show that over the past 1,400 to 1,500 years large earthquakes along the San Andreas Fault have occurred at what intervals?
About 150-year intervals
What were the most widely felt earthquakes in the recorded history of North America?
A series of earthquakes that occurred in 1811-1812 near Missouri.
What type of plate boundary is the San Andreas Fault
Transform plate boundary
What earthquake magnitude would not be felt except by a very few people under favorable conditions?
I. on the Modified Mercalli Scale
What was the intensity and magnitude of the 1906 San Francisco earthquake?
Magnitude of 8.3 on the Richter Scale

Intensity of XI. on the Modified Mercalli Scale
At what magnitudes are earthquakes considered to be potentially damaging?
Earthquakes with a Richter Scale of 5 or higher.
What is believed to be the total accumulated displacement from earthquakes and shifting along the San Andreas Fault since it came into being 15-20 million years ago?
At least 350 miles
The entire San Andreas Fault system is more than ____ long and extends to depths of at least ____ within the Earth.
800 miles, 10 miles
Seismic waves that vibrate with a swinging, side-by-side motion:
Love (L) waves
When one level of a multi-story building collapses and all other floors remain intact:
Which earthquake effect causes the most property damage, injuries, and fatalities?
Ground shaking
Sections of a fault where there have not been any earthquakes for a long period of time:
Seismic gaps
Some change that happens prior to an earthquake:
Who believes that animals are good precursors?
Why was the damage of the 1985 Mexico City earthquake so bad?
Because Mexico City was built over an ancient lakebed; the weak sediments caused liquifaction.
List 5 effects of earthquakes:
1) Ground shaking and rupture
2) Displacement of land surfaces
3) Fires
4) Slope failures (liquifaction/landslides)
5) Tsunami
Earthquake A has a magnitude of 8. Earthquake B has a magnitude of 5. How much less energy does Earthquake A release than Earthquake B?
27000 times
Earthquake A has a magnitude of 3. Earthquake B has a magnitude of 7. How much greater is the size of the vibration of Earthquake B than Earthquake A?
10000 times