Test 3 Flashcards
fault scarp
faults intersect the surface and produce a “step”
normal fault
hanging wall slips down
reverse fault
hanging wall slips up
thrust fault
low angle reverse fault
strike-slip fault
walls slip horizontally
elastic-rebound theory
earthquakes occur because stresses build up, causing rock to bend elastically until either a new fault forms or a pre-existing fault slips, the bent rocks then straighten and vibrate
focus
location where seismic waves first begin to be generated
shallow-focus earthquake
top 60 km of earth
intermediate-focus
60-300 km
deep-focus
down to 660 km
body waves
pass through the interior of the Earth
surface waves
travel along the Earth’s surface
compressional waves
particles move back and forth parallel to the direction the wave propagates
shear waves
particles move back and forth perpendicular to the direction the wave propagates
P-waves
primary compressional body waves
S-waves
secondary shear body waves
R-waves
Rayleigh surface waves that cause the ground to undulate up and down
L-waves
Love surface waves that cause the ground to shimmy back and forth
Earthquake intensity
the degree of ground shaking
Earthquake magnitude
a # that represents the amount of energy released from the seismic source
Moment magnitude
based on the amplitude of several different waves
dimensions of the slipped area
displacement that occurred
Why do earthquakes occur in the Waditi-Benioff zone
shear between sinking lithosphere plate and surrounding asthenosphere
pull exerted by deeper part of the plate
Earthquakes at continental rifts
normal faults
shallow earthquakes
Earthquakes at collision zones
movement along thrust faults
Intraplate earthquakes
stress applied to the boundary of a plate can cause the interior to break suddenly at weak, pre-existing fault zones
The Severity of shaking depends on
magnitude of the quake
distance from the source
nature of the substrate at the location
wavelength of the earthquake waves
sediment liquefaction
happens in wet sand when shaking causes grains to settle together
pressure in the water filling the pores increases
water pushes the grains apart turning the sand into a slurry incapable of supporting weight
geologic structures
features produced by deformation
displacement
a change in location
rotation
change in orientation
distortion
a change in shape
Why do rocks deform brittle or ductile?
temp(warmer = more ductile) pressure(more = more ductile) deformation rate(slow=more ductile) composition
joints
natural cracks
vein
mineral filled crack
dip-slip fault
displacement is parallel to a line going down the slipe of the fault surface
obliqua-slip fault
sliding occurs diagonally on the fault plane
fold
curve in the shape of a rock layer
limb
sides of the fold
hinge
a line along which the curvature of the fold is the greatest