Many geographic and environmental hazards constantly affect and alter the world in which we live. One of the most unpredictable natural disasters to occur is an earthquake. According to Merriam-Webster Collegiate Dictionary, an earthquake is "a shaking or trembling of the earth that is volcanic or tectonic in origin." However, the physical causes, economic and social effects, and costs go far beyond just that dictionary definition.A phenomenon known as tectonic forces is generally what causes an earthquake. Tectonic plates, large sections of the earth's lithosphere, are in gradual, constant motion. As these plates move in opposing directions, areas of subduction, where plates come in contact and slide beneath one another, cause an upward shift in a portion of the earth's crust. Earthquakes generally occur along these fractures of the lithosphere, or faults.Using a seismograph and a formula known as the Richter Scale, scientists measure an earthquake's magnitude. This scale, though it has no specific upper limit, generally ranges from about 1.5, indicating the smallest quake that can be felt, to about 9.0, indicating a severely devastating earthquake. The Richter Scale expresses only an earthquake's seismic strength, not the damage it causes.The effects of an earthquake vary greatly and have numerous contributing factors. A magnitude 8.0 quake centered beneath downtown Los Angeles would do much more damage than a quake of equal strength centered beneath a desolate area of Alaska. Population densities, the design and structure of buildings and roads, and a general preparedness greatly determine the amount of damage any earthquake will do. A highly populated or urbanized area is much more susceptible to widespread damage from an earthquake than a sparsely populated area, simply because there is more to damage. Some of the devastating effects of earthquakes can include structural damage to buildings, buckling of roadways and ...
