Earthquakes Flashcards
What is a convergent boundary?
A location where two tectonic plates move towards each other.
What is a divergent boundary?
A location where two tectonic plates move away from each other.
What is a transform boundary?
A location where two tectonic plates move side by side (horizontally) to each other.
What clues in the landscape can individuals use to determine the direction of plate movement?
They can look at fence and stream displacement, types of damage to buildings, and ground survey data.
How can GPS markers indicate the motion of plates?
GPS provides precise information that can determine the direction and rate of plate movement.
What is a limitation of GPS data to studying earthquakes?
GPS data is only available for a few decades.
How can rock outcrops be used to indicate the motion of plates?
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.
What is a limitation of rock outcrop data?
Plate movement changes in both direction and rate over time, which may not be shown in the rock outcrop positions.
How can plate motion cause earthquakes?
Plates moving relative to each other can grind against each other and store stress in the rocks.
What is one difference in earthquakes produced by convergent boundaries and those produced by transform boundaries?
Earthquakes at convergent boundaries tend to have deeper hypocenters than those at transform boundaries.
Where are most earthquakes located?
Most earthquakes occur along plate boundaries?
Can earthquakes occur in the middle of a plate?
Yes, but these quakes don’t happen as frequently.
On a plate map, how is a convergent boundary shown?
Convergent boundaries are indicated by two arrows that are pointing towards each other.
On a plate map, how is a divergent boundary shown?
Divergent boundaries are indicated by two arrows that are pointing away from each other
On a plate map, how is a transform boundary shown?
Transform boundaries are indicated by two arrows side-by-side that are pointing in opposite directions.
How do scientists compare different earthquakes around the world?
They use the Richter scale, a logarithmic scale that measures energy released during the quake.
How does the amount of ground movement change with a difference of one magnitude?
A difference of 1 magnitude causes 10 times more ground movement. A difference of 2 magnitudes causes 100 times more ground movement.
What is the frequency of earthquakes with a Richter magnitude greater than 8?
Earthquakes with a magnitude greater than 8 are not frequent.
What kind of plate boundary is the San Andreas fault?
A transform boundary
What is a tsunami?
A large ocean wave that forms when earthquakes occur on or near the ocean floor.
What factors determine the amount of earthquake damage?
The geology (bedrock or loose sediment), the type of building construction, and the population of the area.
What does the Modified Mercalli Scale measure about an earthquake?
The Modified Mercalli Scale measures people’s perception of earthquake motion and the amount of damage to buildings and infrastructure.
Why is there an earthquake risk in the middle of a plate?
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
Why is fire a risk during an earthquake?
Earthquake shaking can snap power line or break gas pipelines, which can cause fires.
How are buildings damaged during earthquakes?
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).
How do engineers design structures to withstand earthquakes?
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.
