Measuring and Studying Earthquakes
What tool measures earthquakes?
A seismograph (or seismometer).
What are the giant pieces of Earth’s outer shell called?
Tectonic plates
What is the underground point where an earthquake starts called?
The hypocenter
What is the thin outer layer of the Earth called?
The crust
What material bends instead of snapping during earthquakes and is often used in buildings?
Steel.
What is the recording or graph made by a seismograph called?
A seismogram.
What is it called when two plates pull apart?
Divergent boundary
Why do plates sometimes get “stuck” before an earthquake happens?
Friction locks them together.
Which layer is the only fully liquid layer of the Earth?
The outer core.
What happens during liquefaction?
The ground shakes so much that wet soil acts like a liquid.
What modern scale measures the total energy released in an earthquake?
The Moment Magnitude Scale
What type of boundary causes most earthquakes when plates slide past each other?
Transform Boundary
What kind of energy builds up while plates are stuck and bending?
Elastic potential energy.
What giant layer makes up about 84% of Earth’s volume?
The mantle.
What device gives people a warning before shaking arrives?
ShakeAlert.
Name one of the three things scientists measure to calculate moment magnitude.
The rigidity of the rock, the distance the fault slipped, OR the area of the fault that broke.
About how fast do tectonic plates move each year?
About 2–15 centimeters per year (about as fast as fingernails grow)
What happens when the ocean floor suddenly moves upward during an earthquake?
It can cause a tsunami.
Why is the inner core solid even though it is hotter than the outer core?
Because extreme pressure squeezes the atoms together so they can’t melt.
In the 1906 San Francisco earthquake, what caused most of the damage?
Fires.
Why did scientists stop using the Richter scale for very large earthquakes?
Because it isn’t accurate for very large earthquakes.
What process inside the mantle acts like a conveyor belt and moves the plates?
Mantle Convection
What is the “snap back” of land after it bends and stores energy called?
Elastic rebound.
What two types of crust make up Earth’s outer layer?
Oceanic crust and continental crust.
The 1989 Loma Prieta earthquake happened during what major sporting event?
The World Series.