Chapter 8 - Earthquakes and Earth's Interior

1: What is an Earthquake?

2:Seismology: Study of Earthquake Waves

3: Determining the Size of Earthquakes

5: Earthquake Belts and Plate Boundaries

8: Earth's Layers

1) Faults are "locked" because ________.

A) earthquakes only form when the rocks are free to move

B) high confining pressure increases friction on the fault

C) otherwise they would have earthquakes all the time

D) elastic rebound occurs on faults

B) high confining pressure increases friction on the fault

On a typical seismogram, ________ will show the highest amplitudes.

A) P waves

B) S waves

C) surface waves

D) body waves

C) surface waves

True or False: The Richter earthquake magnitude scale is based on the energy released by the earthquake.

TRUE

Earthquakes with a very deep focus are usually located along ________.

A) a divergent plate boundary such as the Mid-Atlantic Ridge

B) a transform boundary such as the San Andreas

C) a hot spot chain such as the Hawaiian Islands

D) a convergent boundary such as the Peru-Chile trench

D) a convergent boundary such as the Peru-Chile trench

True or False: Oceanic crust is less dense than continental crust.

TRUE

In the 1906 San Francisco earthquake, much of the damage was due to fires because ________.

A) a cow kicked over a lantern in a barn and started the fires

B) water lines were badly damage so that firemen could not put out the fires

C) electric power lines fell and caused sparks that started fires

D) the shaking caused gas lines to rupture everywhere and these ignited to cause huge fire storms in the city

B) water lines were badly damage so that firemen could not put out the fires

Letter A marks the position of the ___________________

EPICENTER

________ is the maximum possible damage designation on the Mercalli scale.

A) XII

B) 3

C) X

D) 10

A) XII

True or False: The ocean ridge systems that make up the major divergent plate boundaries are a source of frequent large earthquakes and tsunamis.

FALSE

Oceanic crust is composed primarily of ________.

A) granite

B) basalt

C) sandstone

D) andesite

B) basalt

When an earthquake occurs, energy radiates in all directions from its source. The source is also referred to as the ________.

A) inertial point

B) epicenter

C) hypocenter or focus

D) seismic zone

C) hypocenter or focus

Which one of the following statements is correct?

A) P waves travel through solids; S waves do not.

B) P and S waves travel through liquids, but P waves do not travel through solids.

C) P and S waves travel through solids and P waves travel through liquids.

D) P and S waves travel through liquids, but S waves do not travel through solids.

C) P and S waves travel through solids and P waves travel through liquids.

True or False: A magnitude scale is a measure of the energy released. It does not measure the extent of building damage or loss of life.

TRUE

Most earthquakes occur along ________ plate boundaries.

CONVERGENT OR SUBDUCTION

Use one of the following five terms to fill in the blanks for the questions below:

Continental crust, Asthenosphere, Mantle, Lithosphere, Oceanic crust

The upper part of the ________ has the approximate composition of granite.

CONTINENTAL CRUST

Major earthquakes are often followed by somewhat smaller events known as ________.

A) aftershocks

B) foreshocks

C) tremors

D) hyposhocks

Aftershocks

Letter D is the point at which ___________________ radiate out from the location of the earthquake.

SEISMIC WAVES

Which of the following is determined by making direct observations in the area affected by an earthquake?

A) epicenter

B) focus or hypocenter

C) magnitude

D) intensity

Name 3 areas on image that have the greatest amount of seismic activity occur?

Circum-Pacific Belt
Alpine - Himalayan Belt
Oceanic Ridges

The inner core is composed of solid iron-nickel even though the temperature of the inner core is greater than the liquid outer core. Why is the inner core solid?

The inner core is a solid due to the immense pressures that exist.

In elastic rebound theory, what must occur to produce an earthquake?

A) Enough stress must build up over time on a fault to overcome friction.

B) Rocks must break in order to produce slip on a fault.

C) The ground needs to absorb enough water to lubricate the surface of the fault.

D) Tidal forces need to be at a maximum to increase the energy applied to the fault.

A) Enough stress must build up over time on a fault to overcome friction.

P waves ________.

A) propagate only in solids

B) are faster than S waves and surface waves

C) have higher amplitudes than do S waves

D) produce the strongest ground shaking

B) are faster than S waves and surface waves

Which of the following is determined by measuring the amplitude of waves recorded from an earthquake?

A) epicenter

B) focus or hypocenter

C) magnitude

D) intensity

C) magnitude

Deep earthquakes in the asthenosphere are normally associated with ______________________________

SUBDUCTION OF OCEANIC CRUST

What is the major difference between the crust and the lithosphere?

A) The crust is cool and the lithosphere is hot.

B) The crust is located above the lithosphere.

C) The crust is located between the lithosphere and the asthenosphere.

D) The crust is compositionally distinct from the mantle, but the lithosphere is the rigid part of the crust and mantle.

D) The crust is compositionally distinct from the mantle, but the lithosphere is the rigid part of the crust and mantle.

Megathrusts between subducting oceanic crust and an overriding plate are a potential source of tsunamis because ________.

A) the earthquakes on these faults are underwater and could displace large amounts of water from the oceans

B) the earthquakes on these faults are underwater and could release large amounts of water from the asthenosphere

C) one side of the fault is on land and the other is underwater so an earthquake could cause a landslide or tsunami depending on which side moved

D) oceanic crust is "thrust" over the continent along a megathrust so that forces the land downward producing a tsunami

A) the earthquakes on these faults are underwater and could displace large amounts of water from the oceans

Letter B marks the position of the ___________________

HYPOCENTER OR FOCUS

Why is the Moment magnitude scale favored over the Richter magnitude scale?

A) The moment magnitude carries the calculated values out to more decimal places so it is more precise.

B) The Richter magnitude is based on older models of seismographs that are no longer used to record earthquakes.

C) The Richter magnitude always underestimates the amount of energy released by an earthquake.

D) The Moment magnitude measures the total energy released by an earthquake.

Use one of the following five terms to fill in the blanks for the question below:

Continental crust, Asthenosphere, Mantle, Lithosphere, Oceanic crust

The upper part of the ________ has the approximate composition of peridotite.

MANTLE

The position on Earth's surface directly above the earthquake source is called the ________.

A) Hypocenter or focus

B) inertial point

C) epicenter

D) seismic zone

C. EPICENTER

________ have the highest velocities

A) Primary waves (P-waves)

B) Secondary waves (S-waves)

C) Surface waves

D) Refracted S-waves

A) Primary waves (P-waves)

Approximately how much more energy is released in a 6.5 Richter magnitude earthquake than in one with a Richter magnitude of 5.5?

A) 900 times

B) 10 times

C) 100 times

D) 30 times

D) 30 times

Use one of the following five terms to fill in the blanks for the question below:

Continental crust, Asthenosphere, Mantle, Lithosphere, Oceanic crust

________ averages 35 to 40 km in thickness.

CONTINENTAL CRUST

Earthquakes along the San Andreas fault zone, for example, are repetitive—they reoccur in roughly the same regions over and over again—separated by decades or centuries because ________.

A) there are areas that are weak and always break when small amounts of energy are applied to them

B) stress continues to build up all the time and when it is great enough to overcome friction there will be an earthquake and then the process will start over again

C) faults are always moving or creeping so an earthquake will occur whenever two sides meet that have the right properties for an earthquake

D) plate boundaries move at regular rates so the interactions across plate boundaries are predictable and regular

B) stress continues to build up all the time and when it is great enough to overcome friction there will be an earthquake and then the process will start over again

Letter C marks the position of ___________________

FAULT

One measurement that is widely used to determine how far the focus of an earthquake is from the seismograph where it is recorded is ________.

A) the amplitude of the P-wave

B) the amplitude of the S-wave

C) the difference in travel time between the P and the S wave

D) the difference in amplitude between the P and the S wave

C) the difference in travel time between the P and the S wave

Use one of the following five terms to fill in the blanks for the question below:

Continental crust, Asthenosphere, Mantle, Lithosphere, Oceanic crust

________ averages roughly 7 km thick.

OCEANIC CRUST

The ________ is the site of initial rupturing associated with an earthquake.

FOCUS

S waves can only travel through __________________ media.

Solid

The Richter magnitude of an earthquake is determined from the ________.

A) duration of the earthquake

B) intensity of the earthquake

C) arrival time of P and S waves

D) amplitude of the largest seismic wave

D) amplitude of the largest seismic wave

Use one of the following five terms to fill in the blanks for the question below:

Continental crust, Asthenosphere, Mantle, Lithosphere, Oceanic crust

________ makes up the largest part of the volume of the earth.

MANTLE

Strike-slip faults are common along ________ plate boundaries.

TRANSFORM

14) Overall, this type of seismic wave is the most destructive.

A) P wave

B) S wave

C) Tsunami

D) surface wave

The Mercalli Scale is a scale from ________.

A) 1 to 12 that rates the energy required for faulting to occur

B) 1 to 10 that rates the energy released by an earthquake

C) I to XII that rates the structural damage due to an earthquake

D) I to X that rates the total energy released during the main quake and all aftershocks

C) I to XII that rates the structural damage due to an earthquake

Use one of the following five terms to fill in the blanks for the question below:

Continental crust, Asthenosphere, Mantle, Lithosphere, Oceanic crust

________ is the weak layer.

ASTHENOSPHERE