Question 1

As a seismologist, you would have expected the Tohoku earthquake to have a shorter rupture in the fault zone as compared to the Sumatra-Andaman earthquake.

Accepted Answer

The Tohoku earthquake in 2011 had a rupture length of about 500 km, while the Sumatra-Andaman earthquake in 2004 had a rupture length of about 1,300 km, making the latter significantly longer.

Question 2

A seismologist would predict that a tsunami produced by an undersea earthquake could travel at 750 kilometers per hour and grow in substantial height as the wave approaches shoreline where friction slows the wave speed down.

Accepted Answer

This is a true statement. Tsunamis have been known to travel as fast as 800 kilometers per hour in deep ocean water and can increase in height as they reach the shore due to the decrease in water depth and increase in friction with the seabed.

Question 3

Where two tectonic plates move past one another, rock near the plate boundary can stretch or compress elastically for decades, and then fracture suddenly and create an earthquake.

Accepted Answer

This is true, as elastic strain builds up along the plate boundary where two plates are moving past each other until the stress is too great and the rock finally ruptures in a sudden release of energy, causing an earthquake.

Question 4

Geologists use a travel-time curve to calculate the distance between the earthquake epicenter and the earthquake focus.

Accepted Answer

Geologists use a travel-time curve to calculate the distance between the earthquake epicenter and seismograph stations, not the earthquake focus. The distance to the focus can only be estimated based on seismic wave arrival times and other data.

Question 5

Seismologists rely on foreshocks as an indicator of when a large earthquake will occur because foreshocks precede all earthquakes and ample seismograph data has been collected on foreshocks.

Accepted Answer

Foreshocks do precede some earthquakes, but not all significant earthquakes have identifiable foreshocks, and predicting the exact timing of an earthquake based on foreshocks remains highly uncertain.

Question 6

Slippage at the New Madrid fault zone caused the 1906 San Francisco earthquake because the fault zones are connected allowing for fracturing to occur.

Accepted Answer

The New Madrid fault zone is located in the central United States, while the San Francisco earthquake occurred along the San Andreas Fault in California. These are two separate fault systems and the San Francisco earthquake was not caused by slippage at the New Madrid fault zone.

Question 7

The most likely source of Earth's magnetism is ____.

Accepted Answer

The flow and convection of liquid metals in the outer core is the leading theory for the source of Earth's magnetism. This movement creates electrical currents, which in turn generates Earth's magnetic field.

Question 8

An area with granite bedrock would be highly prone to liquefaction during a major earthquake.

Accepted Answer

Granite bedrock is a hard and dense material that is not prone to liquefaction during an earthquake. Liquefaction occurs in loose, water-saturated soils, such as sand or silt.

Question 9

Seismologists have found evidence that all of the 30 strongest earthquakes recorded since 1900 have occurred at transform plate boundaries where the impact of colliding plates causes fracturing and faulting of rocks.

Accepted Answer

The statement is false. The 30 strongest earthquakes recorded since 1900 have occurred at subduction zones where one plate is being subducted beneath another plate.

Question 10

In order to determine the epicenter of an earthquake, you would need a minimum of 3 seismograph station seismograms to determine the arrival time of both P and S waves.

Accepted Answer

The answer of In order to determine the epicenter of...

Question 11

A geologist would identify _____________ as the cause of the 2004 Sumatra-Andaman earthquake.

Accepted Answer

A geologist would identify fault rupture as the cause of the 2004 Sumatra-Andaman earthquake. The earthquake occurred along a fault between the Indian and Australian tectonic plates, which caused the plates to rupture and shift, resulting in a massive earthquake.

Question 12

Which procedure is used in short-term predictions of earthquakes?

Accepted Answer

Measurements of changes in the land surface near an active fault zone are used for short-term earthquake predictions. This involves monitoring movements of the Earth's crust near the fault zone to detect any potential activity. The other options listed are not directly related to short-term earthquake prediction methods.

Question 13

If a geologist found evidence of tsunami deposits, submergence of coastal forests from ground displacement, fault rupture, results from computer models and historic documents about an ancient earthquake that occurred in 1700, this would be sufficient data to determine an earthquake occurred at that time.

Accepted Answer

The evidence of tsunami deposits, submergence of coastal forests from ground displacement, fault rupture, and results from computer models and historic documents all point towards the occurrence of an earthquake. Taken together, this evidence would be sufficient to determine that an earthquake occurred in 1700.

Question 14

The monitoring of the electrical conductivity of rock near fault zones is used in long-term predictions of earthquakes and seismologists rely upon this data to help determine where microscopic cracks develop in the rock.

Accepted Answer

The answer of The monitoring of the electrical conductivity of...

Question 15

If a large earthquake with a shallow focus occurred in a region like Haiti that has loose sediments and limited bedrock, the man-made structures created with brick and mortar and concrete that is not reinforced would be a high risk for building failure.

Accepted Answer

Loose sediments and limited bedrock can amplify the shaking of an earthquake, increasing the risk of building failure, particularly for structures that are not reinforced. Bricks, mortar, and concrete used in construction without reinforcement may not withstand the horizontal movement of the ground during an earthquake and are therefore high-risk structures.

Question 16

P and S waves travel more slowly in the Moho than they do in the crust or below the asthenosphere because the composition changes from basalt to peridotite which is a more dense rock material which slows the speed of the body waves down.

Accepted Answer

P and S waves actually travel faster in the Moho and below because peridotite, being denser than the rocks in the crust, allows these waves to propagate more quickly. The increase in density and rigidity of materials like peridotite in the mantle compared to the crustal materials facilitates the faster travel of seismic waves.

Question 17

The boundary in the mantle where composition changes allows seismic wave velocities to do what because pressure is great enough that the minerals in the mantle recrystallize to form denser minerals such as peridotite is called the 660-kilometer discontinuity.

Accepted Answer

The 660-kilometer discontinuity marks a boundary in the mantle where denser minerals, such as peridotite, are formed due to the high pressure. This causes seismic wave velocities to increase.

Question 18

Which of the following building materials normally bend and sway during an earthquake?

Accepted Answer

Steel is designed to be flexible and can bend and sway during an earthquake without collapsing, which helps in absorbing and dissipating seismic energy. Brick, adobe, and stone are more rigid and can crack or crumble under the stress of an earthquake.

Question 19

If you were examining Richter Scale readings from earthquakes at mid-oceanic ridges, you would expect their focus to be deeper and stronger than earthquakes that form at convergent plate.

Accepted Answer

Earthquakes at mid-oceanic ridges are typically shallow and less intense than those that form at convergent plate boundaries. This is because the earthquakes at mid-oceanic ridges are the result of tension and stretching, while those at convergent plate boundaries are the result of compression and subduction.

Question 20

Long-term predictions of when earthquakes will occur are fairly accurate because seismologists have ample seismograph data that indicate specific increments of time between large earthquakes.

Accepted Answer

Long-term earthquake predictions are still not very accurate and often have a wide range of error. While seismologists can identify seismic patterns and areas with higher earthquake activity, there is still much uncertainty in predicting the timing and size of earthquakes.

Quiz 7: Earthquakes and the Earths Structure