Once Upon a time.. Deep under the ground lives the earthquake monster.. It doesn't mean to be scary, but when it moves.. The ground shakes! An earthquake is when the ground suddenly shakes because of movement deep inside the earth.

The earthquake monster lives along a fault! A fault is a crack in the earth where the rocks move. The ground is made of giant pieces called plates. When they get stuck. the monster starts to push.

The rocks don't move right away, first they stretch like a rubber band. This is called elastic deformation (when rocks bend before breaking). THEN SNAP! The plates suddenly move, and the monster ESCAPES!

When the plates move after the monster escapes since the plates moved, the energy in the air travels as seismic waves which are waves that shake the ground. Primary waves are fast and come first, and Secondary waves are slower and shake from side to side. This is where the monster comes out!  

The place underground where the shaking begins is called the focus! (Which is the starting point of the earthquake). The place right above it on the ground is called the Epicenter! Which is where the shaking is the strongest.

Scientists cannot see the escaping Earthquake monster, but they can detect it! They use a seismograph to detect the Earthquake monster which is a machine that records the shaking. When the ground moves, it draws the wiggly lines. Scientists also measure magnitude, which is how strong the earthquake is. This makes them able to detect the Earthquake monster and to help show how powerful the Earthquake is. Earthquakes don't have eruptions like volcanoes! 

The earthquake monster was caught moving... USING PLATE TECTONICS! Plate tectonics are things that show the earth is moving, and sometimes plates get stuck at a fault. Pressure builds up.. then they suddenly slip! This is what causes the earthquakes