Question 1

Transform faults have mostly vertical displacement rather than horizontal displacement.

Accepted Answer

Transform faults primarily exhibit horizontal displacement, where two blocks of the Earth's crust slide past each other horizontally along the fault plane.

Question 2

Large earthquakes do not generate body waves energetic enough to be recorded on seismographs all around the world.

Accepted Answer

Large earthquakes can generate body waves, particularly the primary waves (P waves) which can travel through the Earth's core and be detected by seismographs all around the world. Secondary waves (S waves) can also be recorded, but they are slower and weaker than P waves and are not detected as widely.

Question 3

To describe the location in three-dimensional space of a deformed rock layer or a fault surface,geologists make measurements known as dip and strike.

Accepted Answer

This statement is true. Dip refers to the angle at which the rock layer or fault surface is inclined from horizontal, while strike refers to the orientation of a horizontal line on the surface of the rock layer or fault surface. Together, these measurements can be used to fully describe the orientation of a geological feature in three-dimensional space.

Question 4

The point where a fault first ruptures underground is known as the epicenter.

Accepted Answer

The point where a fault first ruptures underground is actually known as the hypocenter or focus, not the epicenter. The epicenter is the point on the Earth's surface directly above the hypocenter.

Question 5

P- and S-waves do not follow simple paths as they pass through the Earth;they speed up,slow down,and change direction,and S-waves even disappear when they reach the Earth's core.

Accepted Answer

This statement is true. P- and S-waves are affected by the varying density and composition of the Earth's different layers, causing them to change direction and velocity. S-waves can also disappear entirely when they reach the liquid outer core, which cannot transmit shear waves.

Question 6

The shallower the hypocenter,the more P- and S-wave energy will hit the surface,thus putting less energy into Rayleigh waves.

Accepted Answer

The shallower the hypocenter, the more energy is converted into surface waves, including Rayleigh waves, because there is less distance for the energy to dissipate before reaching the surface.

Question 7

The biggest shaking event is called "the earthquake," the smaller ones before it are known as foreshocks,and the smaller ones after it are called aftershocks.

Accepted Answer

This is a correct statement. The earthquake is typically the largest seismic event in a sequence of events that may include foreshocks and aftershocks.

Question 8

Transform faults usually link spreading centers or connect spreading centers with subduction zones.

Accepted Answer

Transform faults are commonly found near or between spreading centers, where new oceanic crust is being formed, or near subduction zones, where oceanic crust is being destroyed. They are able to accommodate the lateral motion of the plates along the divergent or convergent boundary.

Question 9

Moving into the core,P-wave velocities gradually increase until a positive jump is reached at about a 5150-km depth,suggesting that the inner core is solid.

Accepted Answer

The statement is true. The increase in P-wave velocity suggests that the inner core is solid.

Question 10

The Earth's interior is homogeneous.

Accepted Answer

The Earth's interior is not homogeneous. It is composed of different layers with varying compositions and physical properties, such as the crust, mantle, outer core, and inner core.

Question 11

In igneous rocks such as granite,S-waves travel about 1.7 times faster than P-waves.

Accepted Answer

In igneous rocks such as granite, P-waves (primary waves) travel faster than S-waves (secondary waves). P-waves are compressional waves that can travel through both liquid and solid materials, whereas S-waves are shear waves that can only travel through solids, and they typically travel slower than P-waves.

Question 12

Following the paths of P- and S-waves from the Earth's surface inward,there is an initial increase in wave speed but then a marked slowing occurs at a depth of about 100 feet;this defines the top of the lithosphere.

Accepted Answer

This statement is false. The top of the lithosphere is not at a depth of about 100 feet, but rather at a depth of about 60-100 km (37-62 miles) beneath the Earth's surface. The velocity of seismic waves does increase with depth through the Earth's crust and upper mantle, until a decrease in velocity occurs at the top of the asthenosphere, which lies beneath the lithosphere.

Question 13

Aftershocks are smaller than the main shock in an earthquake sequence.

Accepted Answer

Aftershocks are typically smaller in magnitude than the main shock, but can still cause damage and should be taken seriously.

Question 14

Normal faulting occurs when the hanging wall moves upward relative to the footwall.

Accepted Answer

Normal faulting occurs when the hanging wall moves downward relative to the footwall. The correct statement would be "Normal faulting occurs when the hanging wall moves downward relative to the footwall."

Question 15

Both Love and Rayleigh waves are referred to as L waves (long waves)because they take longer periods of time to complete one cycle of motion and are slower moving relative to P- and S-waves.

Accepted Answer

Both statements about Love and Rayleigh waves being L waves and taking longer periods of time to complete one cycle of motion and being slower moving relative to P- and S-waves are true.

Question 16

With their up-and-down and side-to-side motions,S-waves shake the ground surface and can do severe damage to buildings.

Accepted Answer

S-waves, also known as shear waves, can cause severe damage to buildings as they shake the ground surface with their up-and-down and side-to-side motions.

Question 17

The velocity of an S-wave depends on the density and resistance to shearing of materials.

Accepted Answer

This is true. S-waves, also known as shear waves, propagate through materials by causing particles to vibrate perpendicular to the direction of wave propagation. The velocity of these waves is dependent on the density and resistance to shearing of the materials they are passing through. Materials with higher density or greater resistance to shearing will have a higher velocity for S-waves.

Question 18

The shaking produced by Rayleigh waves causes both vertical and horizontal movement.

Accepted Answer

Rayleigh waves cause both vertical and horizontal movement, which can cause damage to buildings and other structures.

Question 19

Passing through the mantle below the asthenosphere,the seismic wave velocities vary but generally increase until about 2900-km depth where P-waves slow markedly and S-waves disappear at the core-mantle boundary zone.

Accepted Answer

This statement is correct. Seismic wave velocities generally increase as they pass through the mantle below the asthenosphere, but then slow down and disappear as they reach the core-mantle boundary zone.

Question 20

It is the horizontal fault movements at subduction zones that most commonly cause tsunami,mostly in the Pacific Ocean.

Accepted Answer

Tsunamis are most commonly caused by vertical displacement of the sea floor due to the subduction of tectonic plates, rather than horizontal fault movements.

Quiz 3: Earthquake Geology and Seismology