EARTHQUAKES June 4, 2009 By Eugenia Meanus

What is an Earthquake In a mild quake the ground will tremble as if a large truck is driving by and you may never notice it. In a more severe quake the ground will shake jolting the house, books cases fall, roads ripple and tree uproot all in mere seconds.

What is an Earthquake Earthquakes happen when plates or rocks within the Earths surface suddenly break or shift under stress, sending shock waves rippling. Most of them are unnoticeable by people. In fact thousands of quakes happen everyday they are just too weak to be felt.

Seismic Waves Is earthquake energy that is transmitted through the Earth. The most common seismic waves include body waves, which transmit energy through the Earth’s interior, and surface waves, which transmit energy along the planet’s surface.

Two types of body waves exist: P waves, which cause rocks in their path to be alternately compressed and expanded in a direction parallel to the wave’s move- ment. S waves, which cause rocks to shear and move perpendicularly to the wave’s direction. v=sZPNjLj8hR8

Seismograph Records the arrival times of seismic waves at a specific location by tracing lines on a seismogram. The Richter scale, which measures earthquake magnitude, is based on the amplitudes of those traced lines. Quakes exceeding magnitude-3.5 can be felt by humans, magnitudes of 6.0 indicate major quakes, and very powerful earthquakes that exceed magnitude-8.0 occur once every 5-10 years.

Common effects of high- magnitude earthquakes: Large ground shifts along faults Landslides Liquefaction (conversion of wet, fine- grained sediment into a fluid mass) Large fast-moving sea waves called tsunami fires

Source: Chernicoff, Stanley; Whitney Donna. Geology; An Intoduction to Physical Geology. Pearson Education Inc., Copyright 2007 You tube x.htm