1 What is an earthquake? Simply put: An earthquake is the shaking of the earth. Free powerpoint template: 1

2 - What causes an earthquake? Earthquakes are the Earth's natural means of releasing stress. Due to the constant motion of the Earth’ plates, this put stress on the edges of the plates. To relieve this stress, the rocks tend to bend, compress, or stretch. Free powerpoint template: 2 An aerial view of the San Andreas fault in the Carrizo Plain, Central California. Picture from

3 - Locatin' the Shakin' Focus: the place on the Earth’s crust where the pressure was released. Underground. Epicenter: the spot on the Earth’s surface directly above the focus. Free powerpoint template: 3

5 Normal Fault Rock above the fault surface moves downward in relation to rock below the fault surface. Sierra Nevada fault Free powerpoint template: 4

6 Reverse Fault Reverse faults result from compression forces that squeeze rock. If rock breaks from forces pushing from opposite directions, rock above a reverse fault surface is forced up and over the rock below the fault surface. Cascadia Free powerpoint template: 5

7 Strike-slip Fault At a strike-slip fault, rocks on either side of the fault are moving past each other without much upward or downward movement. The San Andreas Fault is the boundary between two of Earth’s plates that are moving sideways past each other. Free powerpoint template: 6

8 How does energy created by an earthquake move through the Earth? Seismic waves are energy waves that travel outward from the source of the earthquake. Free powerpoint template: 7

10 P Waves Primary waves (P-waves) cause particles in rocks to move back and forth in the same direction that the wave is traveling. P-Waves are the fastest waves and are felt first, usually as a bang or a thump. Free powerpoint template: 8

11 S Waves Secondary waves (S-waves) move through Earth by causing particles in rocks to move at right angles to the direction of wave travel. These waves are slower than P-Waves and more destructive. AKA Transverse waves Free powerpoint template: 9

12 L Waves Surface waves (L-Waves) or land waves move rock particles in a backward, rolling motion and a side-to-side, swaying motion. Surface Waves reach the earth's surface after P and S waves. Very destructive Free powerpoint template: 10

13 - How are seismic waves measured? Seismic waves from earthquakes are measured with an instrument known as a seismograph. Seismographs register the waves and record the time that each arrived. Free powerpoint template: 11

14 - Measuring Earthquake Magnitude Magnitude is a measure of the energy that is released during an earthquake. Free powerpoint template: 12

15 - Richter Scale The Richter magnitude scale is used to describe the strength of an earthquake and is based on the height of the lines on the seismogram. Free powerpoint template: 13