Earthquakes Flashcards

1
Q

what causes earthquakes?

A

all sorts of causes, fault slip is most common cause

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2
Q

hypocenter vs epicenter

A

hypo: focus
place where fault slip first occurs. earthquake waves expand outward from hypocenter
epicenter: land surface right above the hypo

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3
Q

active vs inactive faults

A

active: ongoing stresses produce motion
inactive: motion occurred in geologic past
not all faults reach surface

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4
Q

where does energy creating earthquakes originate from?

A

rocks break to form new fault
preexisting fault is reactivated
fault remains zone of weakness

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5
Q

friction

A

fault motion stopped by friction
due to bumps along the fault

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6
Q

stick slip

A

faults weaker than surrounding crust
stick: STATIC friction prevents motion
slip: friction briefly overwhelmed by motion

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7
Q

foreschocks

A

precede major earthquakes
smaller tremors indicate crack development in rocks
may warn

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8
Q

displacement

A

greatest near hypocenter
diminishes with distance
faults can offset rocks by 100s of kms over time

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9
Q

p-waves

A

body wave
waves travel by compressing and expanding material
material moves parallel to wave direction
FASTEST
travel through everything

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10
Q

S-waves

A

body wave
waves travel by moving material back and forth
material moves perpendicular to wave travel direction
SLOWER THAN P-WAVES
only travel through solids, not liquids or gases

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11
Q

Love waves

A

surface wave
s-wave that intersects land surface
move ground like writhing snake

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12
Q

Rayleigh waves (r-wave)

A

surface wave
p-wave that intersects land surface
cause ground to ripple up and down like water

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13
Q

seismometer

A

measure wave arrivals and magnitude of motion
magnet and electric coil
record data digitally

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14
Q

seismogram

A

data recording earthquake wave behavior
arrival times determine distance to epicenter

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15
Q

what is the order at which earthquake waves arrive at station?

A

first p-waves
S-waves
surface waves last
time delay between p and s waves used to establish distance to epicenter
point of intersection of stations is the epicenter

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16
Q

mercalli intensity scale

A

amount of shaking damage
1 = low
12 = high

17
Q

SEE SCREENSHOT FOR HOW MOMENT MAGNITUDE SCALE WORKS

18
Q

Plate tectonic boundaries

A

shallow: divergent and transform boundaries
intermediate and deep: convergent boundaries

19
Q

wadati Benioff zone

A

seismically active area in the Earth’s crust where earthquakes occur when two tectonic plates converge and one is subducted beneath the other
intermediate (downgoing slab is cold and brittle)
deep (mineral phase changes create earthquakes)

20
Q

earthquakes at divergent plate boundary

A

normal faults and strike-slip faults are developed

21
Q

transform plate boundary

A

plates slide past each other
occur at shallow crustal levels
transforms link segments of the MOR
on continents = MAJOR DISASTERS

22
Q

san andreas is very active strike-slip fault

23
Q

continental rifts

A

stretching creates normal faults
generate shallow earthquakes similar to MOR

24
Q

collision zones

A

continental crust
orogenic crustal compression
continental lithosphere compresses along thrust faults
orogenic uplift creates landslide hazards

25
which waves cause the most damage?
s waves (stronger motion than p-waves) p-waves: up and down motion s-waves: back and forth motion l-waves: cause ground to writhe like a snake r-waves: ripples, also cause a lot of damage
26
severity of earthquake depends on:
magnitude distance from focus nature of subsurface material TRANSMITTAL OF WAVES QUICKLY = LESS DAMAGE
27
extra damage
landslides and avalanches (steep slopes fail due to shaking) fire disease outbreaks
28
liquefaction
waves liquefy H2O filled sediments groundwater forces grains apart, reducing friction flow as a slurry sand becomes quicksand, and clay, quicklay causes soil to lose strength and land slumps
29
tsunami
result from vertical displacement of sea floor faulting displaces entire volume of overlying water
30
tsunami detection
detectors placed on deep sea floor sense pressure increases from changes in sea thickness
31
earthquake prediction
can be predicted in long term, not in short term (hours or weeks) requires examining evidence of past earthquakes earthquakes do have precursors can't stop them but can be prepared for them