Earthquakes

Question 1

What causes earthquakes (2)

Answer 1

1. Hypocenter

2. Epicenter

Question 2

Hypocenter

Answer 2

the place where fault slip occurs

Question 3

Epicenter

Answer 3

land surface right above the hypocenter

Question 4

Displacement

Answer 4

the amount of movement across a fault
also called “offset”
cumulative over time

Question 5

Fault trace

Answer 5

where the fault reaches the ground surface

not all faults reach the surface

Question 6

Elastic strain

Answer 6

ability of rock to bend without breaking

Question 7

Fault

Answer 7

built up elastic strain is released in a cracking event

Question 8

Asperities

Answer 8

bumps across a surface leading to increased friction

Question 9

Stick

Answer 9

friction prevents movement

Question 10

Slip

Answer 10

friction is briefly overwhelmed by motion

Question 11

InSAR

Answer 11

Interferometric Synthetic Aperture Radar
compares ground elevation changes over time.
display distortion as color bands

Question 12

Major earthquakes may have the following (2)

Answer 12

1. foreshocks

2. aftershocks

Question 13

Body waves (2)

Answer 13

P and S waves

Question 14

P-waves

Answer 14

Primary waves
Travel in earth interior
compress and extend material (slinky)
Travel in solid, liquid, gas

Question 15

S-waves

Answer 15

Secondary waves
travel in earth interior
back and forth movement
travel in solid only

Question 16

Types of seismic waves (2)

Answer 16

1. L-waves

2. R-waves

Question 17

L-waves

Answer 17

Love’s waves (surface waves)
most destructive
surface waves
back and forth movement (snake)

Question 18

R-waves

Answer 18

Reilay waves (surface waves)
move up and down
die out with depth

Question 19

Seismographs

Answer 19

instuments that detect ground motion
measure wave motion and magnitude
vertical motion
horizontal motion

Question 20

Seismogram

Answer 20

data recoding on the piece of paper

P first, S second, surface last

Question 21

Finding the epicenter (3)

Answer 21

• need 3 or more stations to triangulate
• P and S waves come in
• P waves come in first, S-second
• difference between the two show you epicenter distance

Question 22

Earthquake size depends on (2)

Answer 22

1. Magnitude

2. Intensity

Question 23

Magnitude

Answer 23

maximum amplitude of seismograph motion

Question 24

Ricter scale

Answer 24

good when close to epicenter

Question 25

Moment scale

Answer 25

most accurate measure

Question 26

M3 vs M7 earthquakes

Answer 26

earthquakes are logarithmic
M3: 100,000 per year
M7: 32 per year

Question 27

intermediate and deep earthquakes

Answer 27

intermediate: 20-300km
Deep: 300-660 Km

Question 28

San Andreas

Answer 28

Stike-slip Transform fault

hundreds of earthquakes per year

Question 29

Order of wave arrival (4)

Answer 29

1. P-waves
2. S-waves
3. L-waves - Snake
4. R-waves - up/down

Question 30

Wind waves:

Answer 30

influence upper 100m 
wavelength: 10s-100s (meters)*
related to windspeed
10s Km per hour
break in shallow water

Question 31

Tsunami waves:

Answer 31

entire water depth
wavelength: 10s - 100s Km*
uneffected by wind speed
100s Km per hour
arrived as raised plateau