Mercalli_intensity_scale

From Wikipedia, the free encyclopedia Mercalli intensity scale Mercalli intensity scale The Mercalli intensity scale is a scale used for measuring the intensity of an earthquake. The scale quantifies the effects of an earthquake on the Earth’s surface, humans, objects of nature, and man-made structures on a scale of I through XII, with I denoting not felt, and XII one that causes almost complete destruction. The values will differ based on the distance to the earthquake, with the highest intensities being around the epicentral area. Data is gathered from individuals who have experienced the quake, and an intensity value will be given to their location. I. Instrumental II. Feeble Not felt by many people unless in favourable conditions. Felt only by a few people at best, especially on the upper floors of buildings. Delicately suspended objects may swing. Felt quite noticeably by people indoors, especially on the upper floors of buildings. Many do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibration similar to the passing of a truck. Duration estimated. Felt indoors by many people, outdoors by few people during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rock noticeably. Dishes and windows rattle alarmingly. Felt outside by most, may not be felt by some outside in nonfavourable conditions. Dishes and windows may break and large bells will ring. Vibrations like large train passing close to house. Felt by all; many frightened and run outdoors, walk III. Slight Evolution of the Mercalli scale The Mercalli scale originated with the widely used simple ten-degree Rossi-Forel scale, which was revised by Italian volcanologist Giuseppe Mercalli in 1883 and 1902. The terms or Mercalli scale should not be used unless one really means the original ten-degree scale of 1902. In 1902 the ten-degree Mercalli scale was expanded to twelve degrees by Italian physicist Adolfo Cancani. It was later completely re-written by German geophysicist August Heinrich Sieberg and became known as the Mercalli-Cancani-Sieberg (MCS) scale. The Mercalli-Cancani-Sieberg scale was later modified and published in English by Harry O. Wood and Frank Neumann in 1931 as the Mercalli-Wood-Neuman (MWN) scale. It was later improved by Charles Richter, the father of the Richter magnitude scale. The scale is known today as the Modified Mercalli Scale and commonly abbreviated MM. IV. Moderate Modified Mercalli scale The lower degrees of the MM scale generally deal with the manner in which the earthquake is felt by people. The higher numbers of the scale are based on observed structural damage. The table below is a rough guide to the degrees of the Modified Mercalli Scale. The colors and descriptive names shown here differ from those used on certain shake maps in other articles. V. Rather Strong VI. Strong 1 From Wikipedia, the free encyclopedia unsteadily. Windows, dishes, glassware broken; books fall off shelves; some heavy furniture moved or overturned; a few instances of fallen plaster. Damage slight. Mercalli intensity scale masonry and frame structures destroyed with foundation. Rails bent. XI. Very Disastrous Few, if any masonry structures remain standing. Bridges destroyed. Rails bent greatly. Total damage - Almost everything is destroyed. Lines of sight and level distorted. Objects thrown into the air. The ground moves in waves or ripples. Large amounts of rock may move position. VII. Very Strong Difficult to stand; furniture broken; damage negligible in building of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Noticed by people driving motor cars. Damage slight in specially designed structures; considerable in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture moved. General panic; damage considerable in specially designed structures, well designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. Some well built wooden structures destroyed; most XII. Catastrophic Correlations with Physical Quantities The Mercalli scale is not defined in terms of more rigorous, objectively quantifiable measurements such as shake amplitude, peak velocity, acceleration, or period. Information on these has been provided by the USGS Shakemap site. Note that perceived shaking (the basis for the Calligraph scale) is best correlated with acceleration for low-intensity events, and with velocity for high-intensity events. VIII. Destructive See also • Other seismic scales • Hayward Fault Zone for seismic shake maps using the Mercalli scale • Richter magnitude scale IX. Ruinous Bibliography • The Severity of an earthquake pamphlet of the United States Geological Survey • U.S. National Earthquake Information Center • John N. Louie, Associate Professor of Seismology at the University of Nevada X. Disastrous Retrieved from "http://en.wikipedia.org/wiki/Mercalli_intensity_scale" Categories: Seismic scales 2 From Wikipedia, the free encyclopedia Mercalli intensity scale This page was last modified on 15 May 2009, at 01:15 (UTC). All text is available under the terms of the GNU Free Documentation License. (See Copyrights for details.) Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a U.S. registered 501(c)(3) taxdeductible nonprofit charity. Privacy policy About Wikipedia Disclaimers 3