4.1
the difference between p and s waves
p waves compress and expand the ground like an accordion. s waves vibrate from side to side or up and down
The types of stress that occur at each plate boundary
tension, compression, shearing
How the risk of an earthquake is determined
largely depends on how close a given location is to a plate boundary
focus
the area beneath Earth's surface where rock that was under stress begins to break or move
shearing
the stress force that pushes a mass of rock in two opposite directions
The matter p and s waves can travel through
p waves - solids and liquids
s waves - solids
the makeup of a normal fault and a reverse fault and in which direction the footwall and hanging wall move
normal fault - tension, hanging wall moves down
reverse fault - compression, hanging wall moves up
Where earthquakes most often occur
in the Ring Of Fire
epicenter
the point on the surface directly above the focus
normal fault
the fault cuts through rock at an angle, so one block of rock sits over the fault, while the other block lies under the fault
The type of wave that reaches a given location first
p wave
The type of stress that produces reverse faults
comrpession
EXTENDED RESPONSE: explain how a seismograph works
a seismograph works by a pen connected to the weight rests its point on a drum that can rotate. As the drum rotates, the pen in effect draws a straight line on paper wrapped tightly around the drum.
p wave
seismic waves that compress and expand the ground like and accordion
reverse fault
has the same structure as a normal fault, but the blocks move in the reverse direction
The type of wave that arrives second
s wave
How a strike-slip fault occurs
when rocks on either side of the fault slip past each other sideways, with little up or down motion
Vocab: tension
the stress force that pulls on the crust and thins rick in the middle
s wave
seismic waves that can vibrate from side to side or up and down
strike-slip fault
rocks on either side of the fault slip past each other sideways, with little up or down motion
The types of waves that move in an accordion fashion
How fault block mountains form
collision of two plates can cause compression and folding of the crust over a wide area
Vocab: compression
the stress force that squeezes rock until it folds or breaks
surface wave
move more slowly than p and s waves but can produce severe ground movements
plateau
a large area of flat land elevated high above sea level