Earthquake Read Aloud
Science
How do you measure and compare the size of earthquakes? The size can not be judged by solely by the damage to buildings with a number of people killed. That's because a medium earthquake close to a large city will cause more destruction, than will a larger earthquake in an unpopulated area. Seismographs are the instruments that scientists use to measure earthquake shocks. Modern seismographs record their data to a computer and are able to detect a tiny earth tremor, thousands of miles away. Seismologists, ziya of Germany's geoscientific research institute, points to the shockwaves that recorded in blue in this digital graph to the right. On March 28th, 2005, earthquakes off the island of Sumatra. There are hundreds of seismographic stations all over the world that time the interval of earthquake leaves. Scientists use the measurements to find an earthquake's timing, magnitude and location, latitude, longitude, and depth. Scientists use the Richter scale to measure an earthquake's magnitude. The amount of energy it releases, each number on the Richter scale stands for an earthquake that is ten times more powerful than the number below it. You would hardly notice a magnitude minus two earthquake, but a magnitude minus three earthquake is ten times greater and easily felt by everyone. The scale has no upper end, but any earthquake that registers a 6 or more is concerted a major earthquake. The earthquake off island of Sumatra on December 26th, 2004, registered a 9.0 magnitude and caused huge earthquakes. That form sea waves called tsunamis, the enormous earthquake and tsunami waves killed more than 200,000 people and caused immense destruction in several countries. Scientists use observations as well as instruments to measure the effects of an earthquake. The mercalli intensity scale used is observations of the earthquake damage to rated on a scale ranging from one, where the effects are scarcely noticeable to 12 were damaged as total, and the ground heaves in waves, usually the intensity is greatest near the center of the earthquake, and smaller, farther away from the center. But other factors such as the soil in the area, and the construction of the buildings are also important. For example, the earthquake that shook the San Francisco area in October 1989 during the World Series, measured 7.1 on the Richter scale. On the mercalli scale it measured ten to 11 in the marine and district shown here. Where the houses are built a loose soil, but only 6 or 7 in other parts of the city where the houses suffered much less damage.