Earthquakes and Earth's Interior

Question 1

What is an earthquake?

Answer 1

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

Question 2

What are faults?

Answer 2

fractures in Earth’s crust

Question 3

What are seismic waves?

Answer 3

energy from eq that radiates outward of hypocenter/focus

Question 4

epicenter vs hypocenter

Answer 4

epicenter is directly above the hypocenter (abajo)

Question 5

what are the 3 types of seismic waves?

what do they travel through?

Answer 5

P, S , Surface

P&S waves:interior
Surface waves travel along surface

Question 6

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

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

Answer 6

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

speed

Question 7

Seismographs

Answer 7

instruments that detect and record seismic waves

Question 8

seismograms

what are they used to determine

Answer 8

recordings by seismographs

time and location of EQs

Question 9

amplitude

Answer 9

wave height

Question 10

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

Answer 10

surface

Question 11

Which waves leave at the same instant?

Answer 11

pS

Question 12

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?

Answer 12

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

Question 13

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

what kind of graph are you using

Answer 13

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

Question 14

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

Answer 14

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

Question 15

how do you locate an epicenter?

Answer 15

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

Question 16

how do you use a compass to draw circles?

Answer 16

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

Question 17

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

Answer 17

radius=P-S interval

Question 18

how much eq energy originates in narrow zones

Answer 18

95%

Question 19

what is the zone of greatest seismic activity

what’s another zone

Answer 19

circum Pacific belt

alpine-himilayan belt

Question 20

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

Answer 20

pacific

Question 21

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

Answer 21

deep

Question 22

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

Answer 22

shallow

Question 23

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

Answer 23

mid atlantic ridge

Question 24

What is the thickness of the crust?

Answer 24

5-70 km

Question 25

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

Answer 25

mantle | more thaan 82%

Question 26

# ` what kind of rocks make up the mantle

Answer 26

ultramafic

Question 27

how thick is the mantle

Answer 27

2900 km

Question 28

what does rigid mean

Answer 28

stronger/not flexible

Question 29

mantle layers and its characteristics? | upper and lower

Answer 29

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

Question 30

to what depth does the asthenosphere lie

Answer 30

350 km

Question 31

core comp and thickness and state of matter

Answer 31

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

Question 32

what indicates greater rigidity

Answer 32

faster p and S waves (higher velocity)

Question 33

What can't S waves travel through? why?

Answer 33

liquids (outer core) not rigid

Question 34

what can't P waves pass through?

Answer 34

they can pass through ALL layers

Question 35

Why do S waves magically appear in the inner core?

Answer 35

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

Question 36

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

Answer 36

increase

Question 37

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

Answer 37

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

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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

Question 40

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

Answer 40

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

Question 41

temp increases with

Answer 41

depth

Question 42

geothermal gradient

Answer 42

rate of temp increase

Question 43

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

Answer 43

changing

Question 44

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

Answer 44

greater

Question 45

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

Answer 45

the temp stops increasing

Question 46

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

Answer 46

hasnt solid

Question 47

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

Answer 47

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