Aim: What is an earthquake? Do now: In your notes, explain where most earthquakes occur and Why? Japan

Earthquakes - are vibrations in the crust caused by moving crustal plates. California

Focus - the origin (starting point) of the earthquake underground. B. Epicenter – the location on the surface directly above the focus.

II. Causes of Earthquakes the release of potential energy stored in rock. energy is released in all directions

A. Elastic Rebound Hypothesis - Deformation of rocks (stressing/bending) cause them to build up pressure (energy). - When they break, the stored energy is released which results in the vibrations.

III. Measuring Earthquakes Seismology – the study of earthquake waves (energy). Seismographs – instruments that record earthquake waves (energy). *Seismos = earthquake

Seismogram – a graph produced by recording the ground motion on a seismograph.

Creation of Seismogram

Richter Scale: Measures the magnitude (strength) of an earthquake from the seismogram.

IV. Types of Seismic Waves (earthquake waves) epicenter created at the start of the earthquake. What do you notice about the waves in the diagram? wave motion through Earth helps scientists theorize about the inside of Earth and it’s layers.

How would you describe the motion of this wave? A. Body Waves Travel through the Earth’s interior. 1. P-waves (Primary/Compression Waves) push-pull waves that compress and expand the ground in the direction that the waves travel. How would you describe the motion of this wave?

2. S-Waves (Secondary/Transverse Waves) move the ground at right angles (up and down)to the direction that they travel. How would you describe the motion of this wave?

P- Wave S-Wave P & S Wave Animation What can this wave travel through? Travels through solids and liquids Travel Faster Arrives First Travels through solids, Cannot go through Liquids Travel Slower Arrives Second How would you describe the speed of this wave? When does this wave arrive compared to the other?

- Most destructive since they are on the surface B. Surface Waves –seismic waves that travel along the Earth’s outer layers (crust). - Follow P and S waves - Most destructive since they are on the surface China

C. Aftershocks and Foreshocks movements of the crust that follow a major earthquake called aftershocks. small vibrations called foreshocks come before a major earthquake. Anchorage, Alaska

III. Earthquake Zones The “Ring of Fire” is the area that surrounds the Pacific Plate which is marked with volcanoes and earthquakes.

Closure 1: Why could someone think that most earthquakes cause little damage and little loss of life? Because most occur in areas that are not populated by people or cities. Tokyo, Japan

Closure 2: Review Book: p.81-82 #1-10 2. 3. 4. 5. 6. 7. 8. 9. 10. 3 4 3 4 1 1 1 1 2