What is an earthquake caused by?
Movement of rock beneath Earth's surface
What are seismic waves?
They are similar to sound waves, and they travel through Earth carrying energy released by an earthquake.
What partially determines the speed and path of seismic waves?
The material through which the waves travel
What are three types of seismic waves?
P waves, S waves, and surface waves
What is the focus of an earthquake?
The area beneath Earth's surface where rock that was under stress begins to break or move
What is the epicenter of an earthquake?
The point on the surface directly above the focus
What layer of the Earth do most earthquakes begin in?
The lithosphere
Which type of seismic wave is not sent out from the earthquake's focus?
Surface waves
What do P waves do to the ground?
Compress and expand it like an accordion
What are the first waves to arrive from an earthquake?
P waves
How do S waves move?
They move side to side or up and down
How do surface waves move?
Like ocean waves in an almost circular pattern
How do geologists monitor earthquakes?
They measure the seismic waves produced
What is a seismograph?
An instrument that records and measures an earthquake's seismic waves
What does the Modified Mercalli scale rate?
The amount of shaking from an earthquake based on people's observations
What is the magnitude of an earthquake?
A single number that geologists assign to an earthquake based on the earthquake's size
