Question 1

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

Accepted Answer

The magnitude of an earthquake generally increases as the length of the moving fault increases because a longer fault can release more energy.

Question 2

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

Accepted Answer

The Richter scale is logarithmic, meaning each whole number increase on the scale represents a tenfold increase in measured amplitude and roughly 31.6 times more energy release. Therefore, a magnitude 3 earthquake has 10 times the ground motion of a magnitude 2 earthquake.

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?

Accepted Answer

Surface rupture provides direct physical evidence of the fault's location as it is the visible displacement on the ground surface caused by the movement along the fault during an earthquake.

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?

Accepted Answer

The earthquake epicenter being in a remote location means that there were fewer structures and people affected, leading to less damage despite the considerable offset.

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?

Accepted Answer

Scientists are investigating the hypothesis that earthquakes in this region occur in clusters, which suggests a pattern of seismic activity rather than isolated events.

Question 6

Use the following map related to the December 24S1U1P1thS1S1P0, 2004 Sumatra earthquake to answer this question.
 
-How would you characterize the depth of the Sumatra earthquake?

Accepted Answer

The Sumatra earthquake is characterized by a shallow depth, as it occurred at a depth of about 30 kilometers (18.6 miles) below the ocean floor.

Question 7

Use the following map related to the December 24S1U1P1thS1S1P0, 2004 Sumatra earthquake to answer this question.
 
-What is the tectonic reason this earthquake occurred?

Accepted Answer

The earthquake occurred near a subduction zone, where one tectonic plate is being forced under another, leading to significant seismic activity.

Question 8

Use the following map related to the December 24S1U1P1thS1S1P0, 2004 Sumatra earthquake to answer this question.
 
-What type of fault caused the canal damage shown in the following photograph (photo courtesy USGS)?

Accepted Answer

The answer of Use the following map related to the...

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?

Accepted Answer

A larger slip rate typically indicates that a fault is moving more quickly, which generally results in a smaller recurrence interval between seismic events.

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?

Accepted Answer

There is no consistent relationship between slip rate and estimated magnitude, as magnitude is influenced by various factors including fault length and area, not just slip rate.

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.

Accepted Answer

The answer of Three seismograms for a single earthquake with...

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)?

Accepted Answer

The answer of Three seismograms for a single earthquake with...

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?

Accepted Answer

Surface waves cause the ground to move in a rolling motion, similar to waves in the ocean, and are typically felt near the epicenter.

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?

Accepted Answer

The Richter scale is logarithmic, meaning each whole number increase represents a tenfold increase in measured amplitude. Therefore, a magnitude 5 earthquake generates 100 times more ground motion than a magnitude 3 earthquake.

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?

Accepted Answer

The earthquake in city B would cause more shaking farthest from the epicenter because it is far from a plate boundary, meaning there are fewer faults to absorb and dissipate the seismic energy, allowing it to travel farther.

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?

Accepted Answer

Liquefaction occurs when loose, saturated soil loses its strength and behaves like a liquid. This is most likely to happen near the water, where the soil is saturated and loose.

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?

Accepted Answer

The answer of Analyze the foci indicated by the arrows...

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?

Accepted Answer

The reported numbers are limited by technology because smaller magnitude earthquakes are harder to detect and may not be recorded as frequently as larger ones.

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.

Accepted Answer

Vibrations are a key concept in understanding earthquakes, as they are the waves generated by the sudden release of energy in the Earth's crust.

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.

Accepted Answer

The answer of Complete the concept map by selecting the...

Quiz 5: Earthquakes

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

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

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?

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?

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) ?

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?

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?

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?

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

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?

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.

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.

Quiz 5: Earthquakes

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

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

Use the following map related to the December 24th, 2004 Sumatra earthquake to answer this question. -How would you characterize the depth of the Sumatra earthquake?

Use the following map related to the December 24th, 2004 Sumatra earthquake to answer this question. -What is the tectonic reason this earthquake occurred?

Use the following map related to the December 24th, 2004 Sumatra earthquake to answer this question. -What type of fault caused the canal damage shown in the following photograph (photo courtesy USGS) ?

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?

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?

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?

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

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?

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.

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.

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?

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?

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) ?