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<br /> Hazard Mitigation Plan | 2022 <br />Earthquake Hazards <br />- 49 - <br />Image: Magnitude Scale <br />(Source: USGS) <br /> <br /> <br />The second scale is the Modified Mercalli (MM) Intensity Scale. According to the US Geological <br />Survey, this scale consists of a series of certain key responses such as people awakening, <br />movement of furniture, damage to chimneys, and finally - total destruction. Although numerous <br />intensity scales have been developed over the last several hundred years to evaluate the effects <br />of earthquakes, the one currently used in the United States is the Modified Mercalli (MM) Intensity <br />Scale. It was developed in 1931 by the American seismologists Harry Wood and Frank Neumann. <br />This scale, composed of increasing levels of intensity that range from imperceptible shaking to <br />catastrophic destruction, is designated by Roman numerals. It does not have a mathematical <br />basis; instead it is an arbitrary ranking based on observed effects. <br /> <br />The Modified Mercalli Intensity value assigned to a specific site after an earthquake has a more <br />meaningful measure of severity to the nonscientist than the magnitude because intensity refers <br />to the effects actually experienced at that place. The lower numbers of the intensity scale <br />generally deal with the manner in which the earthquake is felt by people. The higher numbers of <br />the scale are based on observed structural damage. Structural engineers usually contribute <br />information for assigning intensity values of VIII or above. Below is an image of the scale. <br />