Chapter 5: Earthquake's and Earth's Interior

Earthquakes with a Richter magnitude of less than ______ are generally not felt by humans.

2.0

How does a seismograph work? Choose all that apply.

A seismograph works by suspending a weight from bedrock, which remains motionless during an earthquake. A rotating drum that is affixed to the moving bedrock moves as the rock moves, recording the relative displacement between the stationary weight and the rotating drum. A seismograph can measure P waves, S waves, and surface waves.

What is an earthquake? Under what circumstances do most large earthquakes occur?

An earthquake is ground shaking caused by sudden and rapid movement along Earth fractures called faults. Most large earthquakes occur when there are huge amounts of stored energy in the rocks that suddenly is released.

How much more energy does a magnitude 7.0 earthquake release than a magnitude 6.0 earthquake?

An earthquake with a magnitude of 7.0 releases 32 times more energy than an earthquake with a magnitude of 6.0.

What causes an earthquake?

Earthquakes result when a block of rock rapidly slips past another along a fault plane.

What is meant by elastic rebound?

Elastic rebound refers to how slippage along a fault (i.e., earthquake) allows the deformed rock to regain its original shape.

List at least three reasons an earthquake with a magnitude of 7.0 might cause more death and destruction than a quake with a magnitude of 8.0.

Fire - fire can break out with a magnitude of 7.0 Earthquake can create a firestorm which fans out due to wind Tsunami - earthquake that is triggered at a mega thrust fault will create a tsunami which leads to larger damage Landslide - ground is converted and it slumps away. Major destruction follows.

In addition to the destruction created directly by seismic vibrations, list three other types of destruction associated with earthquakes.

Fire, landslides and ground subsidence, and seismic sea waves (tsunamis) are all capable of adding to the destructive nature of earthquakes.

What does the Modified Mercalli Intensity scale tell us about an earthquake?

How intense an earthquake feels.

What information is used to establish the lower numbers on the Modified Mercalli Intensity scale?

How the earthquake is felt by people in an area.

Which type of fault tends to produce the most destructive earthquakes?

Megathrust fault

Which type(s) of plate boundary is(are) associated with Earth's largest earthquakes? Choose all that apply.

Ocean-oceanic convergent plate boundary Oceanic-continental convergent plate boundary

How does triangulation determine the epicenter of an earthquake?

On a map, a circle is drawn around each of three recording stations, with the radius being the distance from the station to the epicenter of the earthquake. The epicenter is located where the three circles intersect.

What are the differences between P waves, S waves, and surface waves?

P waves are the fastest and have the lowest amplitudes; S waves are the second-fastest and have the second-lowest amplitudes; surface waves are the slowest and have the highest amplitudes.

Which of the following terms are types of seismic waves? Choose all that apply.

Secondary waves, Surface waves and Primary Waves

How are faults, hypocenters, and epicenters related?

Slippage of rocks that generate earthquakes occur along faults. The hypocenter is the place slippage occurs between the rocks and the epicenter is the location on Earth's surface directly above the hypocenter.

Which type(s) of seismic waves tend(s) to cause the greatest destruction to buildings?

Surface waves

Which is the zone of the greatest amount of seismic activity?

The circum-Pacific belt

What information does a time-travel graph determine?

The distance from the earthquake to the recording station.

Why is the moment magnitude scale favored over the Richter scale for large earthquakes?

The moment magnitude scale measures the total energy released, whereas the Richter scale only measures the amplitude of the largest seismic wave.

Explain why an earthquake east of the Rockies may produce damage over a larger area than one of similar magnitude in California.

The reason is that the underlying bedrock in the central and eastern United States is older and more rigid. As a result, seismic waves are able to travel greater distances with less attenuation than in the western United States.

Which of the following does not determine the amount of destruction caused by seismic shaking?

Type of fault

What is a tsunami? How are tsunamis generated?

a series of water waves that travel away from a fault in all directions at high speed. through displacement of the seafloor under water.

The location of earthquake epicenters closely correlates with the __________________.

edges of the plates

List four factors that influence the amount of destruction that seismic vibrations cause to human-made structures.

intensity of shaking. duration of shaking. nature of the material upon which the structure rests. nature of building materials and the construction practices of the region.

The Modified Mercalli Intensity Scale is used to measure _______.

the amount of damage caused by an earthquake