Mr. Longoria's Earth Science

As mentioned in the previous post, a seismograph is used to determine the magnitude of an earthquake and the location of the epicenter. Because earthquakes produce different types of wave motion, a modern seimograph station usually has three seismographs. One rrecords up-and-down motions, another records side-to-side motion in a north-south direction, and a third records side-to-side motion in a east-west direction. The sheet used to record the motion of an earthquake is called a seismogram . This sheet is placed on a rotating drum that turns slowly by a clock. Above the paper is a pen with its point resting on top of the sheet and drum. The pen rest stationary attached to a heavy weight. When the drum moves due to the shaking of the ground, the paper moves and the pen produces a zig-zag line on the paper. Interpreting a Seismograph Because P-waves move faster than S-waves, the P-waves always arrive at a seismograph station before the S-waves. Seismologists use the difference in the

Recent events in Haiti, have shown us the vast destruction and lost of life that a major earthquake causes. The 2010 Haiti earthquake was a catastrophic magnitude 7.0 Mw earthquake . Its epicenter was near the town of Léogâne , approximately 25 km (16 miles) west of Port-au-Prince , Haiti's capital. The earthquake occurred at 16:53 local time (21:53 UTC ) on Tuesday, 12 January 2010. By 24 January, at least 52 aftershocks measuring 4.5 or greater had been recorded. An estimated three million people were affected by the quake; news states that 200,000 people have been identified as dead and that an estimated 300,000 injured have been treated so far. It is also estimated that 250,000 residences and 30,000 comercial buildings have collapsed or severely damaged. Most earthquakes result from the strain that builds up at tectonic plate boundaries. More than 3 million earthquakes occur each year. Most of these are too small to be noticeable. Each year, however, a number of powerful e