Earthquakes

Question 1

What is a convergent boundary?

Answer 1

A location where two tectonic plates move towards each other.

Question 2

What is a divergent boundary?

Answer 2

A location where two tectonic plates move away from each other.

Question 3

What is a transform boundary?

Answer 3

A location where two tectonic plates move side by side (horizontally) to each other.

Question 4

What clues in the landscape can individuals use to determine the direction of plate movement?

Answer 4

They can look at fence and stream displacement, types of damage to buildings, and ground survey data.

Question 5

How can GPS markers indicate the motion of plates?

Answer 5

GPS provides precise information that can determine the direction and rate of plate movement.

Question 6

What is a limitation of GPS data to studying earthquakes?

Answer 6

GPS data is only available for a few decades.

Question 7

How can rock outcrops be used to indicate the motion of plates?

Answer 7

Rock outcrops that formed at the same time but are found at different locations on each side of a fault can indicate the direction of plate movement.

Question 8

What is a limitation of rock outcrop data?

Answer 8

Plate movement changes in both direction and rate over time, which may not be shown in the rock outcrop positions.

Question 9

How can plate motion cause earthquakes?

Answer 9

Plates moving relative to each other can grind against each other and store stress in the rocks.

Question 10

What is one difference in earthquakes produced by convergent boundaries and those produced by transform boundaries?

Answer 10

Earthquakes at convergent boundaries tend to have deeper hypocenters than those at transform boundaries.

Question 11

Where are most earthquakes located?

Answer 11

Most earthquakes occur along plate boundaries?

Question 12

Can earthquakes occur in the middle of a plate?

Answer 12

Yes, but these quakes don’t happen as frequently.

Question 13

On a plate map, how is a convergent boundary shown?

Answer 13

Convergent boundaries are indicated by two arrows that are pointing towards each other.

Question 14

On a plate map, how is a divergent boundary shown?

Answer 14

Divergent boundaries are indicated by two arrows that are pointing away from each other

Question 15

On a plate map, how is a transform boundary shown?

Answer 15

Transform boundaries are indicated by two arrows side-by-side that are pointing in opposite directions.

Question 16

How do scientists compare different earthquakes around the world?

Answer 16

They use the Richter scale, a logarithmic scale that measures energy released during the quake.

Question 17

How does the amount of ground movement change with a difference of one magnitude?

Answer 17

A difference of 1 magnitude causes 10 times more ground movement. A difference of 2 magnitudes causes 100 times more ground movement.

Question 18

What is the frequency of earthquakes with a Richter magnitude greater than 8?

Answer 18

Earthquakes with a magnitude greater than 8 are not frequent.

Question 19

What kind of plate boundary is the San Andreas fault?

Answer 19

A transform boundary

Question 20

What is a tsunami?

Answer 20

A large ocean wave that forms when earthquakes occur on or near the ocean floor.

Question 21

What factors determine the amount of earthquake damage?

Answer 21

The geology (bedrock or loose sediment), the type of building construction, and the population of the area.

Question 22

What does the Modified Mercalli Scale measure about an earthquake?

Answer 22

The Modified Mercalli Scale measures people’s perception of earthquake motion and the amount of damage to buildings and infrastructure.

Question 23

Why is there an earthquake risk in the middle of a plate?

Answer 23

Faults located in the middle of a plate formed along ancient plate boundaries. Since the entire plate is moving, the faults can still shift and produce earthquakes

Question 24

Why is fire a risk during an earthquake?

Answer 24

Earthquake shaking can snap power line or break gas pipelines, which can cause fires.

Question 25

How are buildings damaged during earthquakes?

Answer 25

Buildings with large open areas (building lobbies or parking garages) can collapse or pancake. Building frames can shift in the direction of ground motion. Some tall buildings can shake and collapse if their natural frequency matches the frequency of the earthquake waves (resonance).

Question 26

How do engineers design structures to withstand earthquakes?

Answer 26

They use materials strong enough to withstand moderate earthquakes and structural supports to prevent shifting, crumbling, or pancaking. Engineers also place foundations on bedrock rather than sediment to provide stability.