Earthquakes

· The sudden shaking and trembling that results from the sudden movement of the Earth’s crust

· Estimated that more than 1 million occur every year

o About 1 every 30 seconds

· Are commonly caused by faults

o A break in the Earth’s crust

· Cause Tsunamis: Large Ocean Waves

Seismic Waves

· Primary Waves: P-waves

o Travel fastest

o Move through solids, liquids, and gas

· Secondary Waves: S-Waves

o Arrive after P-Waves

o Travel only through solid, absorbed by liquids

· Surface Waves: L-Waves

o Move slowest

o Originate at Epicenter

o Move like ocean waves

o * Cause Most Damage*

Measuring Seismic Waves

· Seismograph: An instrument that detects and measures seismic waves

· Seismologist: scientist who studies seismic waves

· Seismogram: record of seismic waves

· Richter Scale: Scale use to measure strength of Earthquake

o 1-10

o 1= least destructive

o 6+ = high damage

Damage

· Amount of damage depends on the earthquakes strength, rock and soil type, population, building types, time of day

· Focus

o Actual point on a fault where movement occurs and vibrations occur

o Located deep within Earth’s surface

· Epicenter

o Point on surface directly above focus

o Damage is greatest at or near the epicenter

· Intensity

o A measure of how much damage an earthquake causes

o Mercalli Intensity Scale

§ Measures how intense an Earthquake was