Earthquakes Chapter 8 Earthquake - vibration of the earth caused by slippage along a fault. Characteristics 1. Focus- point in the Earth where a quake begins. 2. Epicenter- point on the surface above the focus. 3. Aftershock- small quake following a major quake. 4. Foreshock- small quake before a major quake. Cause Elastic Rebound Hypothesis - release of energy stored in deformed rocks.

Elastic Rebound Hypothesis

Slippage along a fault

Measuring Quakes 1. Detection - Seismograph – instrument that records earthquake waves. Wave Types 1. Surface Waves- waves on Earth’s outer layer. 2. Body Waves- waves in Earth’s interior. - P Waves- push-pull waves(1st) - S Waves- waves acting at right angles(2nd)

Seismograph

Seismogram

Types of Waves

2. Locating Epicenter - 3 or more seismograph stations measure the time it takes for waves to travel. 3. Magnitude - Richter Scale - measures strongest recorded waves - Moment Magnitude - measures energy released

The Richter Scale Richter Magnitude TNT Energy Equivalent Example   Richter Magnitude TNT Energy Equivalent Example 1.0 6 ounces 1.5 2 pounds 2.0 13 pounds 2.5 63 pounds 3.0 397 pounds 3.5 1,000 pounds 4.0 6 tons Small Atomic Bomb 4.5 32 tons Average Tornado 5.0 199 tons 5.5 500 tons Massena, NY, 1994 6.0 6270 tons 6.5 31,550 ton Coalinga, CA, 1983 7.0 199,000 tons Hebgen Lake, MT 1959 7.5 1,000,000 tons 8.0 6,270,00 tons San Francisco, CA 1906 8.5 31,550,000 tons Anchorage, AK, 1964 9.0 199,999,000 tons

Locating Earthquakes

Dangers of Earthquakes 1. Liquefaction - wet soil turns liquid - causes ground to collapse 2. Tsunami - vibrations create giant ocean waves 3. Landslide - vibrations cause soil to break loose

TSUNAMI

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