Deck 5: Earthquakes

Question 1

What happens to earthquake magnitude as the length (size) of the moving fault changes?

A) Magnitude decreases as fault length increases.
B) Magnitude remains constant as fault length changes.
C) Magnitude increases as fault length increases.
D) Magnitude increases as fault length decreases.

Answer 1

Magnitude increases as fault length increases.

Question 2

All else being equal, what is the difference in ground motion between Richter magnitude 2 and 3 earthquakes?

A) Ground motion increases 1 times the magnitude 2 motion.
B) Ground motion increases 10 times the magnitude 2 motion.
C) Ground motion increases 100 times the magnitude 2 motion.

Answer 2

Ground motion increases 10 times the magnitude 2 motion.

Question 3

Read the following exert from a USGS report concerning a recent earthquake and answer this question.
Special Report: The Hector Mine Earthquake, 10/16/1999
A M7.1 earthquake occurred at 2:46 a.m. local time on 10/16/1999.
The event was located in a remote, sparsely-populated part of the Mojave Desert of California,
approximately 47 miles east-southeast of Barstow and 32 miles north of Joshua Tree (see map next page).
The initial magnitude estimate of 7.0 was upgraded to 7.1 on October 18, 1999, based on in-depth analysis
of "teleseismic" data recorded worldwide.
The earthquake occurred on the Lavic Lake fault, one of a series of north-northwest trending faults
through the eastern Mojave shear zone. Geologists from the U.S. Geological Survey and Southern
California Earthquake Center were able to fly over the rupture (which is within the Twenty Nine Palms
Marine Base) on the afternoon of October 16 and documented a 40-km long surface rupture. The aerial
photos show an apparent maximum offset of 3.8-4.7 meters. These preliminary estimates for both fault
length and slip are consistent with expectations for a magnitude 7.0 earthquake, although the slip is
perhaps somewhat larger than average. The fault is one of a series of closely spaced, northwest-trending,
right-lateral strike slip faults that traverse this portion of the Mojave Desert. Together, these faults within
what is termed the Mojave Shear Zone serve to relieve a small portion of the stresses that build up along
the boundary between the Pacific and North American tectonic plates.
An interesting aspect of the Hector Mine earthquake is that it occurred only 7 years after the 1992 Landers
and Joshua Tree earthquakes, which occurred on similar faults within the Mojave Shear Zone. This
apparent clustering of earthquakes may be purely coincidental, but scientists are conducting research to
see if this kind of earthquake behavior is typical of this region. That is, perhaps many of the Mojave Shear
Zone faults produce earthquakes within a short time interval (perhaps spanning several hundred or more
years), followed by several thousands of years of quiescence.


-What evidence was used to identify the exact location of the fault responsible for the earthquake?

A) Teleseismic data
B) Reported by local population
C) Surface rupture
D) Previous history of earthquakes

Answer 3

Surface rupture

Question 4

Read the following exert from a USGS report concerning a recent earthquake and answer this question.
Special Report: The Hector Mine Earthquake, 10/16/1999
A M7.1 earthquake occurred at 2:46 a.m. local time on 10/16/1999.
The event was located in a remote, sparsely-populated part of the Mojave Desert of California,
approximately 47 miles east-southeast of Barstow and 32 miles north of Joshua Tree (see map next page).
The initial magnitude estimate of 7.0 was upgraded to 7.1 on October 18, 1999, based on in-depth analysis
of "teleseismic" data recorded worldwide.
The earthquake occurred on the Lavic Lake fault, one of a series of north-northwest trending faults
through the eastern Mojave shear zone. Geologists from the U.S. Geological Survey and Southern
California Earthquake Center were able to fly over the rupture (which is within the Twenty Nine Palms
Marine Base) on the afternoon of October 16 and documented a 40-km long surface rupture. The aerial
photos show an apparent maximum offset of 3.8-4.7 meters. These preliminary estimates for both fault
length and slip are consistent with expectations for a magnitude 7.0 earthquake, although the slip is
perhaps somewhat larger than average. The fault is one of a series of closely spaced, northwest-trending,
right-lateral strike slip faults that traverse this portion of the Mojave Desert. Together, these faults within
what is termed the Mojave Shear Zone serve to relieve a small portion of the stresses that build up along
the boundary between the Pacific and North American tectonic plates.
An interesting aspect of the Hector Mine earthquake is that it occurred only 7 years after the 1992 Landers
and Joshua Tree earthquakes, which occurred on similar faults within the Mojave Shear Zone. This
apparent clustering of earthquakes may be purely coincidental, but scientists are conducting research to
see if this kind of earthquake behavior is typical of this region. That is, perhaps many of the Mojave Shear
Zone faults produce earthquakes within a short time interval (perhaps spanning several hundred or more
years), followed by several thousands of years of quiescence.


-There was considerable offset caused by this earthquake but little damage caused by this earthquake. Why?

A) The earthquake epicenter was in a remote location.
B) The earthquake occurred early in the morning.
C) The earthquake had a shallow focus.
D) Stress was relieved along the Mojave Shear Zone.

Question 5

Read the following exert from a USGS report concerning a recent earthquake and answer this question.
Special Report: The Hector Mine Earthquake, 10/16/1999
A M7.1 earthquake occurred at 2:46 a.m. local time on 10/16/1999.
The event was located in a remote, sparsely-populated part of the Mojave Desert of California,
approximately 47 miles east-southeast of Barstow and 32 miles north of Joshua Tree (see map next page).
The initial magnitude estimate of 7.0 was upgraded to 7.1 on October 18, 1999, based on in-depth analysis
of "teleseismic" data recorded worldwide.
The earthquake occurred on the Lavic Lake fault, one of a series of north-northwest trending faults
through the eastern Mojave shear zone. Geologists from the U.S. Geological Survey and Southern
California Earthquake Center were able to fly over the rupture (which is within the Twenty Nine Palms
Marine Base) on the afternoon of October 16 and documented a 40-km long surface rupture. The aerial
photos show an apparent maximum offset of 3.8-4.7 meters. These preliminary estimates for both fault
length and slip are consistent with expectations for a magnitude 7.0 earthquake, although the slip is
perhaps somewhat larger than average. The fault is one of a series of closely spaced, northwest-trending,
right-lateral strike slip faults that traverse this portion of the Mojave Desert. Together, these faults within
what is termed the Mojave Shear Zone serve to relieve a small portion of the stresses that build up along
the boundary between the Pacific and North American tectonic plates.
An interesting aspect of the Hector Mine earthquake is that it occurred only 7 years after the 1992 Landers
and Joshua Tree earthquakes, which occurred on similar faults within the Mojave Shear Zone. This
apparent clustering of earthquakes may be purely coincidental, but scientists are conducting research to
see if this kind of earthquake behavior is typical of this region. That is, perhaps many of the Mojave Shear
Zone faults produce earthquakes within a short time interval (perhaps spanning several hundred or more
years), followed by several thousands of years of quiescence.


-What is the current hypothesis scientists are investigating with regard to this fault system?

A) Earthquake magnitudes determined from fault-slip and teleseismic observations are similar.
B) Strike-slip faults in the Mojave Shear Zone relieve stress along the North American and Pacific plates.
C) Earthquakes in this region occur in clusters.
D) This is a region of quiescence.

Question 6

Use the following map related to the December 24^th, 2004 Sumatra earthquake to answer this question.


-How would you characterize the depth of the Sumatra earthquake?

A) Shallow depth
B) Moderate depth
C) Deep

Question 7

Use the following map related to the December 24^th, 2004 Sumatra earthquake to answer this question.


-What is the tectonic reason this earthquake occurred?

A) It is near a transform boundary.
B) It is near a subduction zone.
C) It is near a mid-ocean ridge.

Question 8

Use the following map related to the December 24^th, 2004 Sumatra earthquake to answer this question.


-What type of fault caused the canal damage shown in the following photograph (photo courtesy USGS)?

A) Normal fault
B) Reverse fault
C) Strike-slip

Question 9

Analyze the table below that shows USGS data for earthquake zones in Alaska and use it to answer this question.


-What is the trend when comparing slip rate to recurrence interval?

A) The larger the slip rate the smaller the recurrence interval
B) The larger the slip rate the larger the recurrence interval
C) There is no obvious slip-rate, recurrence relationship

Question 10

Analyze the table below that shows USGS data for earthquake zones in Alaska and use it to answer this question.


-What is the trend when comparing slip rate to estimated magnitude?

A) The larger the slip rate the smaller the estimated magnitude
B) The larger the slip rate the larger the estimated magnitude
C) There is no obvious slip-magnitude relationship.

Question 11

Three seismograms for a single earthquake with an epicenter in Columbia are shown below. The data are from stations that were at very different distances from the epicenter. Arrows denote arrival of P and S waves. Note: Vertical scales are not all the same.


-Place the seismograms in order based on their distance from the epicenter, closest to farthest away.

A) A,B,C
B) B,C,A
C) C,B,A
D) A,C,B

Question 12

Three seismograms for a single earthquake with an epicenter in Columbia are shown below. The data are from stations that were at very different distances from the epicenter. Arrows denote arrival of P and S waves. Note: Vertical scales are not all the same.


-Which seismic wave arrived between 11-12 on the bottom seismogram (station ASCN)?

A) P-wave
B) S-wave
C) Surface wave

Question 13

Three seismograms for a single earthquake with an epicenter in Columbia are shown below. The data are from stations that were at very different distances from the epicenter. Arrows denote arrival of P and S waves. Note: Vertical scales are not all the same.


-Suppose you were near the epicenter and felt the Earth move as if you were in the ocean. What type of seismic wave would you have experienced?

A) P-wave
B) S-wave
C) Surface wave

Question 14

Three seismograms for a single earthquake with an epicenter in Columbia are shown below. The data are from stations that were at very different distances from the epicenter. Arrows denote arrival of P and S waves. Note: Vertical scales are not all the same.


-How much more ground motion does a Richter magnitude 5 earthquake generate compared to a Richter magnitude 3 earthquake?

A) 2 times
B) 5 times
C) 10 times
D) 100 times

Question 15

Three seismograms for a single earthquake with an epicenter in Columbia are shown below. The data are from stations that were at very different distances from the epicenter. Arrows denote arrival of P and S waves. Note: Vertical scales are not all the same.


-Suppose two earthquakes with the same magnitude, depth, and relative motion occur in two cities, A and B. City A is near a plate boundary, city B is far from a plate boundary. Which earthquake would cause the
Most shaking farthest from the epicenter?

A) The one in city A because there are many nearby faults
B) The one in city A because there are few nearby faults
C) The one in city B because there are many nearby faults
D) The one in city B because there are few nearby faults

Question 16

The map below shows the predicted liquefaction probability near Oakland, CA, for a hypothetical magnitude 7.1 earthquake on the Hayward fault. Use it to answer this question.


-Why is the probability of liquefaction highest near the water?

A) Because that is where a tsunami may occur
B) Because that location has saturated, loose material
C) Because that location is farthest from the fault

Question 17

Analyze the foci indicated by the arrows on the graph displayed below. What type of plate boundary is present between 180-190 degrees longitude?

A) Divergent
B) Convergent
C) Transform
Analyze the earthquake data graphed below and answer the question. The data displayed here are for recorded earthquakes from November to December in 2006. Earthquake magnitudes are binned such that 2 includes all magnitudes from 2 to less than 3, magnitude 3 includes those from 3 to less than 4 and so forth.

Question 18

You learned in class and in the reading that smaller magnitude earthquakes occur more frequently than larger magnitude earthquakes. So why do these actual data show fewer magnitude 2 and 3 earthquakes than magnitude 4 earthquakes?

A) The scientists who made that observation were wrong.
B) The reported numbers are limited by technology.
C) This region only experiences larger earthquakes.

Question 19

Complete the concept map by selecting the correct responses from the lists provided.


-Complete the concept map by selecting the correct responses from number 1.

A) Cracks in the Earth
B) Vibrations
C) Foci
D) Epicenters

Question 20

Complete the concept map by selecting the correct responses from the lists provided.


-Complete the concept map by selecting the correct responses from number 2.

A) Cliffs
B) Coasts
C) Faults
D) Epicenters

Question 21

Complete the concept map by selecting the correct responses from the lists provided.


-Complete the concept map by selecting the correct responses from number 3.

A) Plate boundaries
B) Coasts
C) Faults
D) Epicenters

Question 22

Complete the concept map by selecting the correct responses from the lists provided.


-Complete the concept map by selecting the correct responses from number 4.

A) 10's km
B) 100's km
C) 1000's km

Question 23

Complete the concept map by selecting the correct responses from the lists provided.


-Complete the concept map by selecting the correct responses from number 5.

A) Normal or reverse fault
B) Strike-slip fault
C) Locked fault

Question 24

Complete the concept map by selecting the correct responses from the lists provided.


-Complete the concept map by selecting the correct responses from number 6.

A) Normal or reverse fault
B) Strike-slip fault
C) Locked fault

Question 25

Complete the concept map by selecting the correct responses from the lists provided.


-Complete the concept map by selecting the correct responses from number 7.

A) 10's meters
B) 100's meters
C) 1000's meters

Question 26

Complete the concept map by selecting the correct responses from the lists provided.


-Complete the concept map by selecting the correct responses from number 8.

A) Vertically
B) Horizontally
C) Above one another

Question 27

Complete the concept map by selecting the correct responses from the lists provided.


-Complete the concept map by selecting the correct responses from number 9.

A) Fault scarp
B) Crack
C) Canyon

Question 28

Complete the concept map by selecting the correct responses from the lists provided.


-What type of plate boundary is most likely to generate a tsunami?

A) convergent
B) divergent
C) transform

Question 29

-Analyze the above schematic map for an earthquake. Where is the epicenter of the earthquake?

A) Tulsa
B) Memphis
C) Richmond

Question 30

-Analyze the above schematic map for an earthquake. Which seismometers are needed to find the epicenter?

A) Memphis only
B) Memphis and Richmond
C) Memphis, Richmond and Tulsa

Question 31

-This type of fault movement is the most likely to result in a fault scarp.

A) Strike-slip fault
B) Reverse fault
C) Transverse fault

Question 32

-Suppose you were standing on a solid surface when P waves from a nearby earthquake arrived and you could feel them. What ground motion sensation would you feel?

A) The ground would move vertically beneath you, moving you up and down.
B) The ground would move horizontally beneath you, shaking you side to side.
C) The ground would move both vertically and horizontally at the same time.

Question 33

-Suppose you were standing on a solid surface when S waves from a nearby earthquake arrived and you could feel them. What ground motion sensation would you feel?

A) The ground would move vertically beneath you, moving you up and down.
B) The ground would move horizontally beneath you, shaking you side to side.
C) The ground would move both vertically and horizontally at the same time.

Question 34

-Suppose you read this description of an earthquake from the 1880's. "The ground shook so hard that books fell off the desk." Which scale would be most appropriate for this type of information?

A) Mercalli
B) Richter
C) Moment

Question 35

-What does moment earthquake magnitude measure?

A) Energy released from earthquake
B) Amplitude of seismic waves on seismogram
C) Damage resulting from an earthquake
D) Displacement on faults

Question 36

-What is the Mercalli Intensity scale based upon?

A) Damage and human reports
B) Seismic wave amplitude
C) Measurements from seismometers

Question 37

-Suppose three identical magnitude 3 earthquakes occur in three different locations. The epicenters are Anchorage (Alaska), Los Angeles (California) and Boston (Massachusetts). Which location would most likely experience the largest intensity the farthest from the epicenter?

A) California
B) Alaska
C) Massachusetts

Question 38

-Suppose two identical magnitude 6 earthquakes occur in two different locations. The locations are San Diego, California and Istanbul, Turkey. Based on what you know from this chapter, which location would likely suffer the most casualties and why?

A) San Diego because building codes are better enforced than in Istanbul.
B) San Diego because building codes are less enforced than in Istanbul.
C) Istanbul because building codes are better enforced than in San Diego.
D) Istanbul because building codes are less enforced than in San Diego.

Question 39

-This earthquake-generated hazard can occur when seismic waves shake saturated soils.

A) Liquefaction
B) Uplift
C) Tsunami

Question 40

-Consider the 26 December, 2004 Indonesia earthquake where over 200,000 people died. If there had been an adequate tsunami warning system, how much time would there have been to get people to higher ground?

A) From a few hours to a few days.
B) From a few minutes to a few hours.
C) There was not enough time to get people to safety.

Question 41

Earthquakes can be predicted using present-day technology.

Question 42

P and S waves are both body waves.

Question 43

Magnitude is a measure of the size of an earthquake while intensity deals with the earthquake's effect on humans.

Question 44

The earthquake magnitude system has a maximum value of 9.

Question 45

Earthquakes can occur in any location.

Question 46

Rocks near faults can deform before they rupture.

Question 47

Earthquake hazard maps are based on probability.