By Andrea Snell Revised by GBrenneman S and How they shape the Earth By Andrea Snell Revised by GBrenneman

Earthquakes are a sudden movement of Earth’s crust that releases energy. CA quake The crust of the Earth is constantly moving, but are usually slow – until a major earthquake takes place. About 95% of all earthquakes occur at or near the edge of moving plates. Worldwide Earthquake Locator They occur along cracks in the Earth’s crust called faults. Faults are associated with, or form, the boundaries between Earth’s tectonic plates. Earthquakes do not occur randomly.

How do earthquakes work ?

Types of stress in the Earth’s crust lead to fault lines.

Types of Faults Strike-slip faults Normal Faults Reverse Faults

Modeling Fault Types Foam Fault Models and Examples

Normal Faults animation of normal fault Normal Faults create space. Two pieces of the crust pull apart, spreading the crust apart.

Reverse Faults animation of reverse fault Reverse faults squeeze the crust and push two blocks of crust on top of one another. Usually these faults are found in the Rocky Mountains and Himalayas and cause mountains to form.

Strike-slip faults animation of strike-slip fault Indicates rocks are sliding past each other, with little to no vertical movement. Both the San Andreas and Anatolian Faults are strike-slip.

Epicenter and Focus video lecture The epicenter is the point the Earth’s surface, or land, directly above the earthquake focus. The focus is the hypocenter of an earthquake. The vibrating waves travel away from the focus of the earthquake and move in all directions. Earthquakes do not start at the epicenter.

Earthquake Waves The energy from an earthquake travels away from the focus in waves. The waves travel in different speeds. There are two types of waves 1. Those that travel inside the Earth 2. Those that travel only at the surface

Waves that travel inside the Earth Demo of S waves and P waves Primary Waves, or P Wave, are “push-pull” waves that cause back-and- forth vibrations in the same direction as the waves move. The P-Waves are fast-moving. Secondary Waves, or S waves, cause vibrations at right angles to the waves direction of travel. The S waves are slow- moving.

Surface Waves Surface waves explanation Surface waves- only travel only at the surface and move slower than P-waves or S-waves. These waves make the ground roll and sway. They can cause a great deal of damage to buildings, roads, and other surface features. pool shakes

Locating an Earthquake Lab Preview for epicenter lab

Measuring Earthquakes Earthquakes are recorded by instruments called seismographs. Seismographs record seismic waves. The motion is measured electronically and recorded in a computer. They can measure both S and P waves. The size of the waves is called magnitude. To tell the strength of the earthquake scientists use a Richter Scale. The larger the number on the Richter Scale, the larger the earthquake. You won’t even feel an earthquake if it is below a 3. Today scientists also use the Moment-Magnitude scale. NASA sci file Each number is 32 times greater than the previous number. 4.0 -Would shake your house like a large truck passes by. 5.0 – Things might fall off shelves. Walls might crack and windows break. 7.0 – Weaker buildings could collapse. Also cracks may occur in streets. 8.0 – Buildings and bridges could fall down and large cracks in surface. 9.0 and up- Large scale damage and cities flattened.

Testing Buildings for Earthquake-Proofing

Japan’s Mega Earthquake Japan's Mega Earthquake (48 mins.)

Tsunamis can be caused by earthquakes Japan's tsunami and how it happened (documentary)

How to Protect Yourself during an Earthquake Protect Yourself (interactive game) Animation of how to stay safe

Landforms created by Earth’s stresses Part Two

Mountain Building mountain building (clip) Fault-Block Mountains: When normal faults uplift a block of rock, a fault-block mountain forms. The Grand Tetons in Wyoming and Idaho are one such example.

More mountains Folds are compressions from two plates colliding. The Appalachian Mountains were formed in this way.

Anticlines and Synclines Anticlines and Synclines can be found in folded mountains. Anticlines, such as the Black Hills in South Dakota, are the folds in the rock that bend upward while synclines, such as the Illinois Basin, are the folds in the rock that bend downward.

Plateau - a large area of flat land elevated high above sea level How the Grand Canyon Was Formed

Science is so Cool! earthquake exhibit