Earthquakes EARTHQUAKE 101

Focus This is the origin of an earthquakes location. It is where it begins. Remember, all earthquakes start underground.

Epicenter The point on the ground surface directly above the focus is known as the epicenter.

Primary Waves Primary waves are the fastest waves. They are also called P-Waves. P-waves move through solids, liquids, and gases.

Secondary Waves The second waves that are recorded by a seismograph are secondary waves or S-waves. S-waves move slower than P-waves S-waves move through solids only.

Surface Waves Surface waves move along the Earth’s surface. Surface waves are also known as Long waves, or L-waves. These waves are the last to be recorded. L-waves can move through solids causing Earth’s surface to rise and fall like ocean waves.

DISCUSS Take a few minutes and discuss the 3 types of seismic waves with your group. Compare the seismic waves to what happens when you toss a rock into a pond. FIST TO FIVE CHECK?

The Richter Scale The Richter scale shows an earthquake’s relative strength, or magnitude. Developed in 1935 by a geologist named, Charles Richter. On this scale an earthquake is given a number between 1 – 10.

Tsunami A large ocean wave caused by an earthquake.

Before and After pictures of Japanese Tsunami Intro to Japan's tsunami Real time video of incoming Japanese tsunami-primary and secondary waves Incoming Tsunami-Surface waves

What Causes Earthquakes?

Tectonic Plate Movement Tectonic plate movement along fault lines causes earthquakes. Rocks on both sides of the fault are squeezed together. Pressure on rocks increases. Eventually the rocks break at their weakest point releasing energy. This energy is in the form of vibrations/waves.

Faults There are four kinds of faults

A normal fault is a fault along which the movement is vertical A normal fault is a fault along which the movement is vertical. Plates move in an up and down movement. Normal Fault

A reverse fault is a fault in which the crust above the fault plane rises in relation to the crust below. Reverse Fault

Strike-Slip Fault A strike-slip fault is a fault along which the movement is horizontal. These plates move side to side.

Thrust-Fault A thrust fault is a low-angle reverse fault (also called a dip slip).

THE END