Earthquakes Flashcards
Earthquakes are…
the release of energy stored as elastic deformation of rocks
propagated by seismic waves
a measurement of size based on the maximum amplitude of seismograph waves.
Magnitude
Magnitude is described using different scales. Which is the most accurate?
Richter Scale (Best near epicenter) Moment magnitude scale—most accurate.
Earthquakes are caused by…
magma movement, volcanic eruptions, landslides,
meteorite impacts, and nuclear detonations
The Hypocenter (Focus)
the location where fault slip occurs.
the land surface directly above the hypocenter. Maps
often portray the location of these things.
Epicenter
On a normal fault…
the hanging wall moves down relative to the footwall. It most often results from extension (pull-apart or stretching).
In a reverse fault…
the hanging wall moves up relative to the footwall. It usually results from compression (squeezing or shortening).
A thrust fault is…
A special kind of reverse fault (lower slope angle)
strike-slip fault
one block slides laterally past the other block. There is no vertical motion across the fault.
Shallow—divergent and transform boundaries; Intermediate and deep—convergent boundaries
Mid-ocean ridges (divergent)
Earthquakes are rare below 660 km as the mantle becomes too ductile.
the Wadati-Benioff zone (earthquakes that trace the path of the subducting crust)
P-waves
travel by compressing and expanding the material parallel to the wave-travel direction. The fastest seismic waves and they travel through solids, liquids, and gases.
travel by moving material back and forth, perpendicular to the wave-travel direction. These are slower and travel only through solids.
S-Waves
What are the two body waves?
S-waves and P-waves
What are the two surface waves?
L-waves, R-waves
the slowest and most destructive waves
L-waves (Which are a type of S-wave)
These waves cause the ground to ripple up and down like water. Type of P-wave
R-Waves
An instrument that measures ground movement
Seismometer
Cause the ground to go up and down. First to arrive
P-waves
Cause the ground to shake back and forth. Second to arrive.
S-Waves
Cause extensive damage. Much stronger than the first waves that arrive
S-waves
These waves follow quickly behind the S-waves
L-waves
These are the last waves to arrive. These
waves usually last longer than the other kinds and usually cause extensive damage.
R-waves
Liquefaction…
causes soil to lose strength. Land, and the structures on it, will slump and flow.
Can we predict earthquakes?
Yes AND No. They CAN be predicted long term, NOT short term.
Tsunami (harbor wave) results from…
displacement of the sea floor by an earthquake, submarine landslide, or volcanic explosion that displaces the entire volume of overlying water
