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<br /> Hazard Mitigation Plan | 2022 <br />Earthquake Hazards <br />- 48 - <br />Earthquake Hazards <br />Hazard Definition <br />An earthquake is a sudden motion or trembling <br />that is caused by a release of strain accumulated <br />within or along the edge of the Earth's tectonic <br />plates. The effects of an earthquake can be felt <br />far beyond the site of its occurrence. They usually <br />occur without warning and, after just a few <br />seconds, can cause massive damage and <br />extensive casualties. Common effects of <br />earthquakes are ground motion and shaking, <br />surface fault ruptures, and ground failure. <br /> <br />There are two tools used to describe earthquake <br />intensity. The first is the Magnitude Scale, which <br />is sometimes referred to as the Richter Scale. The <br />two are similar but not exactly the same. The <br />Magnitude Scale was devised as a means of rating earthquake strength and is an indirect <br />measure of seismic energy released. The Scale is logarithmic with each one-point increase <br />corresponding to a 10-fold increase in the amplitude of the seismic shock waves generated by <br />the earthquake. In terms of actual energy released, however, each one-point increase on the <br />Richter scale corresponds to about a 32-fold increase in energy released. Therefore, a Magnitude <br />7 (M7) earthquake is 100 times (10 X 10) more powerful than a M5 earthquake and releases <br />1,024 times (32 X 32) the energy. <br /> <br />Image: Richter Scale <br />(Source: USGS) <br />