Chapter 9 Flashcards
What is an earthquake?
When rock stress builds up so much to the point where the rocks either bend, compress, or stretch. They cause vibrations in the ground.
What moves the tectonic plates?
Convection currents in the mantle
Where do most earthquakes occur?
Along fault lines
What type of plate boundary is associated with deep earthquakes?
Convergent plate boundaries
What type of plate boundary is associated with shallow earthquakes?
Divergent plate boundaries
What does the Richter Scale measure?
Magnitude of an earthquake (ranges from 1 and keeps going higher, but the highest magnitude yet was a 9.5)
What does the Modified Mercalli Scale measure?
Intensity of an earthquake (ranges I - XII)
What is the elastic rebound theory?
The elastic rebound theory is when there is a buildup of potential energy in a fault, and once that energy is released, it triggers an earthquake. This causes the rocks to deform, but after the earthquake, the rocks return back to their original shape.
In normal and reverse faults, where is the hangwall located?
Above the fault
In normal and reverse faults, where is the footwall located?
Below the fault
Where does the hangwall move in a normal fault?
It slips downward
Where does the hangwall move in a reverse fault?
It slides up
What is an example of a strike-slip fault?
The San Andreas fault
What are the two types of strike-slip faults? (maybe not on the test)
Left-lateral strike-slip fault and right-lateral strike-slip fault
What is the focus of an earthquake?
The focus is the starting point of the earthquake, where a rock breaks underground which releases energy that results in an earthquake.
What are seismic waves?
Sound waves that are released by an earthquake that travels through the Earth.
What is the epicenter of an earthquake?
The point on the surface of the Earth directly above the focus. This area experiences the most violent seismic waves and faces the most damage because this is where the seismic waves reach first.
How are seismic waves measured?
Using a seismograph
What are the two types of seismic waves?
Body waves and surface waves
What are the two types of body waves?
P-waves (slang for primary waves) and s-waves (slang for secondary waves)
What are the two types of surface waves?
Love waves and Rayleigh waves
Which seismic waves travels the fastest?
Primary waves
Which states of matter can p-waves travel through?
Solids, liquids, and gases
How do p-waves move?
In a push and pull accordion-like motion. They compress then expand in a horizontal motion.
Why are primary waves called primary waves?
Because they are the first waves to arrive at seismic graphing stations
What are p-waves also known as?
Seismic longitudinal waves
Which states of matter can s-waves travel through?
Solids
Where do s-waves travel?
They travel along the surface of the earth
Are p-waves or s-waves stronger?
S-waves are stronger but slower
How do s-waves move?
They move in an up and down vertical motion like a rollercoaster. They also do the most amount of damage due to their vertical movement.
Why are secondary waves called secondary waves?
Because they arrive at the seismic graphing station second.
Where do surface waves travel?
The surface
How do love waves move?
They move in a horizontal back-and-forth motion (like a snake)
How do Rayleigh waves move?
They move similarly to ocean waves. Kind of like the s-wave motion, but with an elliptical pattern.
Which of the two surface waves is the most destructive?
Love waves
Which seismic wave lasts the longest?
Rayleigh waves last the longest because they are spread out
What type of vibrations do surface waves cause and what does this result in?
They release low-frequency vibrations which causes low buildings to shake
Which seismic waves come directly from the focus?
Body waves (p-waves and s-waves)
Which seismic waves come from the epicenter?
Surface waves (love waves and rayleigh waves)
What type of vibrations do compressional and shear waves cause? (maybe not on the test)
They cause high-frequency vibrations which causes tall buildings to shake
How is the epicenter of an earthquake located?
They look at the interval between s-waves and p-waves. If there is a lot of time in between the two waves, you are farther away from the earthquake and vice versa. Using this information, you can calculate where the epicenter is.
How many seismographs are needed to locate the epicenter?
Three. This is a process called triangulation, which “…uses distance information determined from 3 seismic stations to uniquely locate the earthquake.”
What is a shadow zone?
A shadow zone is an area on earth where seismographs cannot detect any seismic waves. This might occur because the waves bend or simply stop.
What is magnitude?
“[a] measure of energy released by an earthquake”
Who invented the Richter Scale?
Charles Richter
What was the highest magnitude of an earthquake ever recorded?
9.5 (earthquake in Chile)
Do most earthquakes have a high or low magnitude?
Low
How much more energy has to be released for the magnitude of an earthquake to increase by 1.0?
32x
What is liquefaction ?
When shaking from an earthquake causes wet soil to turn into a liquid
What natural disaster occurs sometimes after an earthquake?
A tsunami
What are moorings?
Circular structures made of rubber and steel located under a building to absorb some of the impact of the earthquake so the building doesn’t collapse
What is the difference between a seismograph and a seismogram?
A seismograph is the machine itself while the seismogram is the paper where the lines are drawn.
What is a moho?
The boundary between the crust and the mantle
Where is the focus of an earthquake located?
The crust
What creates shadow zones?
When p-waves bend or s-waves stop
Why are shadow zones able to form?
Because seismic waves travel in all directions, so a bending or blockage of one causes a shadow zone
Between what degrees from the earthquake focus do shadow zones exist?
105 degrees-140 degrees (of no seismic waves)
Why do seismic waves bend or stop?
Each layer of the earth has a different density, and the density affects the wave
What is the relationship between the depth, density and pressure?
Density increases with depth as pressures increase.
