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GEO LAB > Earthquakes and Earth's Interior > Flashcards

Earthquakes and Earth's Interior Flashcards

1
Q

What is an earthquake?

A

ground shaking caused by sudden movement of rocks slipping past another along faults

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2
Q

What are faults?

A

fractures in Earth’s crust

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3
Q

What are seismic waves?

A

energy from eq that radiates outward of hypocenter/focus

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4
Q

epicenter vs hypocenter

A

epicenter is directly above the hypocenter (abajo)

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5
Q

what are the 3 types of seismic waves?

what do they travel through?

A

P, S , Surface

P&S waves:interior
Surface waves travel along surface

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6
Q

Which seismic wave has the greatest velocity? Middle? Last?

velocity aka
reach the seismograph stations first? Middle? Last?

A

P (reach seismograph station first)
S (Second)
Surface (Last)

speed

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7
Q

Seismographs

A

instruments that detect and record seismic waves

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8
Q

seismograms

what are they used to determine

A

recordings by seismographs

time and location of EQs

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9
Q

amplitude

A

wave height

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10
Q

Which waves have the greatest amplitude and therefore are the most dangerous

A

surface

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11
Q

Which waves leave at the same instant?

A

pS

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12
Q

What is the relationship btw the arrival times of the first P wave compared to the first surface wave as the distance btw the hypocenter and seismograph increases?

A

there will be greater difference btw arrival times; the s waves and surface waves might not show up until a while

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13
Q

How do you determine the distance btw a recording station and an epicenter?

what kind of graph are you using

A
  1. Determine the P-S wave interval (time elasped from 1st P wave to first S wave)
  2. On the y-axis, draw a line from 0 to whatever time interval
  3. Draw ticks on a piece of paper and slide it btw the 2 lines (P at bottom), make sure paper is straight
  4. once both ticks line up, record the distance from epicenter and time from epicenter to reach station

travel-time graph

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14
Q

using the travel-time graph, how can you find low long it took for the first P wave to reach the station?

A

knowing the interval btw the 1st P and S wave, use paper with line of that interval, then stop and record distance of P wave curve only! when ticks meet up with lines

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15
Q

how do you locate an epicenter?

A
  1. get seismograms from 3 dif stations
  2. calculate distance from station to epicenter
  3. use compass to draw 3 circles
  4. point where all 3 circles connect is the epicenter
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16
Q

how do you use a compass to draw circles?

A

use the scale at bottom
start from 0 and extend pencil to the number of miles/unit from the epicenter to that station
repeat for other stations’ circles

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17
Q

how can you check to make sure your circle is correct?

A

radius=P-S interval

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18
Q

how much eq energy originates in narrow zones

A

95%

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19
Q

what is the zone of greatest seismic activity

what’s another zone

A

circum Pacific belt

alpine-himilayan belt

20
Q

do most deep earthquakes occur along: the marigin of the atlantic or pacific basin

A

pacific

21
Q

do the eqs that occur along the western margin of the s.america get deeper or shallower inland

A

deep

22
Q

at what depth (shallow, intermediate, or deep) do eqs in the middle of the atlntic ocean occur?

A

shallow

23
Q

with what geological feature are the eqs in the mid atlantic associated

A

mid atlantic ridge

24
Q

What is the thickness of the crust?

A

5-70 km

25
Q

What is the layer of the earth that contains the most volume

%

A

mantle

more thaan 82%

26
Q

`

what kind of rocks make up the mantle

A

ultramafic

27
Q

how thick is the mantle

A

2900 km

28
Q

what does rigid mean

A

stronger/not flexible

29
Q

mantle layers and its characteristics?

upper and lower

A

lithosphere: rigid/strong
asthenosphere: weak, hot
^upper
lower: more rigid as depth increases

30
Q

to what depth does the asthenosphere lie

A

350 km

31
Q

core comp and thickness and state of matter

A

iron-nickel
inner: solid, 1216km
outer: liq 2270km

32
Q

what indicates greater rigidity

A

faster p and S waves (higher velocity)

33
Q

What can’t S waves travel through? why?

A

liquids (outer core) not rigid

34
Q

what can’t P waves pass through?

A

they can pass through ALL layers

35
Q

Why do S waves magically appear in the inner core?

A

when P waves are btw inner and outer core, some energy is converted to S waves

36
Q

does the velocity of p waves and s waves increase or decrease with increased depth in the lithosphere

A

increase

37
Q

Does the velocicty of P and S waves increase or decrease immediately below the lithosphere and why

A

decrease
lithosphere is more rigid than the asthenosphere, so velocity decreasess

38
Q

when looking at the velocities of the waves, what should you do? ASKKKKKKKK

A

follow the line, the line that hits it from left to right isn’t the first

39
Q

Do P waves increase or decrease in veleocity as they enter the outer core and why

A

decrease upon entering (mantle is rigid to liq outer core) then start to increase inside outer core

40
Q

How do S and P waves behave when entering the inner core

A

increase in velocity at border btw outer and inner, then increase slowly

41
Q

temp increases with

A

depth

42
Q

geothermal gradient

A

rate of temp increase

43
Q

does earth’s internal temp increase at a constant or changing rate with increasing depth?

A

changing

44
Q

is the rate of temp increase from the surface to 100 km greaater than or less than the rate of increase below 100 km

A

greater

45
Q

how do you know when a rock has reached its melting temp from a graph

A

the temp stops increasing

46
Q

does the melting curve for basalt indicate that the lithosphere above 100 km has or hasn’t reached the melting temp for basalt? is this layer soliid or magma

A

hasnt
solid

47
Q

does the graph you constructed support or refute the concept of a weak astehnosphere that can flow

A

supports bc the lithosphere is solid sisnce basalt and granite haven’t reached melt.point, but at some depth in the asthenosphere (160km) it does, so its magma

GEO LAB (12 decks)

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