Geology 101 Quiz 14

Question 1

earthquakes occur when

Answer 1

stresses build up inside the earth to point where they exceed the strength of the surrounding rock, or exceed the force of friction holding two sides of a fault in place

Question 2

red colored dots (the deepest earthquakes) on an earthquake map are associated with

Answer 2

subduction zones

Question 3

red dots on the left side of a plate boundary mean which plate is being subducted?

Answer 3

the right side plate

Question 4

the subducting plate will always be on the same side as

Answer 4

the trench

Question 5

seismic waves

Answer 5

aka ground waves; generated when rock is flexed and snaps back into place after the rock breaks or slides along a fault

Question 6

elastic rebound

Answer 6

flexed rock snaps back into place after a rupture

Question 7

slip

Answer 7

the amount of displacement

Question 8

P waves (primary waves)

Answer 8

compressional waves; do not form the traditional “S” shape of an ocean wave, but compress and expand rock as they travel - like a slinky

Question 9

which type of seismic waves are the fastet?

Answer 9

P waves (primary waves)

Question 10

P waves travel through the earth’s

Answer 10

liquid outer core

Question 11

S waves (secondary waves)

Answer 11

have the characteristic “S” shape of an ocean wave

Question 12

S waves are (slower/faster) than P waves

Answer 12

slower

Question 13

S waves travel through

Answer 13

solids, but not liquids

Question 14

P waves travel through

Answer 14

solids and liquids

Question 15

surface waves

Answer 15

also have the characteristic “S” shape, but travel only along the surface

Question 16

slowest waves that cause the most damage

Answer 16

surface waves

Question 17

seismic waves are measured using a

Answer 17

seismometer/seismograph

Question 18

P waves are (back and forth/up and down)

Answer 18

back and forth

Question 19

S waves are (back and forth/up and down)

Answer 19

up and down

Question 20

focus

Answer 20

location where the slip occurred beneath the surface

Question 21

epicenter

Answer 21

point on the surface directly above the focus

Question 22

which scale is preferred by many geophysicists?

Answer 22

Moment Magnitude Scale

Question 23

the Richter Scale provides a measurement of the energy of an earthquake where?

Answer 23

at the epicenter

Question 24

each number on the Richter Scale is ? times more powerful than the previous number

Answer 24

10 (logarithmic scale)

Question 25

on the Richter Scale, we can feel an earthquake starting at about magnitude ? and earthquakes are destructive starting at about magnitude ?

Answer 25

3; 5

Question 26

the Modified Mercali Scale is a measure of

Answer 26

the destructiveness of an earthquake where felt

Question 27

the Richter scale has no theoretical limits and reported intensities can include decimal values, but the Mercali scale is divided into ? discrete categories

Answer 27

12

Question 28

roman numerals up through twelve

Answer 28

one I
two II
three III
four IV
five V
six VI
seven VII
eight VIII
nine IX
ten X
elevel XI
twelve XII

Question 29

on the modified Mercalli scale, intensity level I description

Answer 29

not felt except by a very few under especially favorable conditions

Question 30

modified Mercalli scale intensity level VI description

Answer 30

slight damage; felt by all

Question 31

modified Mercalli scale intensity level XII description

Answer 31

damage total; lines of sight and level are distorted; objects thrown into the air

Question 32

seismic waves attenuate (?) more as they travel through ? than through ?

Answer 32

grow weaker; rock than through unconsolidated sediments

Question 33

do earthquakes kill people directly? if not, what does?

Answer 33

no; collapsing buildings, fire, landslides, tsunamis

Question 34

are tallest buildings at greatest risk?

Answer 34

no

Question 35

how can a fire start during an earthquake?

Answer 35

ruptured gas lines

Question 36

what are the two ways earthquakes can generate tsunamis?

Answer 36

1. If a submarine normal, reverse, or thrust fault slips, water will be displaced and generate a wave (the slippage causes the tsunami, not the seismic waves).
2. An earthquake can shake loose sediment causing a submarine landslide. The ocean surface suddenly drops above the source of the slide, and is suddenly elevated above where the slide travels, both creating a large wave.

Question 37

waves from a tsunami (weaken/strengthen) as they radiate

Answer 37

weaken

Question 38

early warning tremors help predict earthquakes because

Answer 38

small earthquakes often precede big earthquakes

Question 39

how does the seismic gap method help predict earthquakes?

Answer 39

big earthquakes sometimes occur at approximately regular intervals

Question 40

how does monitoring movement and stress along faults help predict earthquakes?

Answer 40

when a segment of a fault slips, stress increases on adjacent locked segments; if segments slip in sequence, the next slip point may be predicted

Question 41

one unique use of seismic waves is the detection of ?

Answer 41

underground nuclear weapons testing

Question 42

nuclear blasts yield a high-energy initial ? that dies out rapidly, with very little ?

Answer 42

P-wave; S-waves

Question 43

seismic waves help to monitor volcanoes: setting off blasts or striking the ground on one side of the volcano and then measuring the seismic waves on the other side helps because

Answer 43

P waves will pass through liquid magma and S waves will not; by analyzing the “shadow” created by missing S waves, the size of the magma chamber and any changes over time can be monitored

Question 44

seismic waves help us to explore the earth’s

Answer 44

interior