the building (or other structure) design,.Some factors that affect the amount of damage that occurs are: To investigate earthquakes that occurred before there were seismometers. To help distinguish it from magnitude scales, the MMI scale uses roman numerals.Īlthough the Mercalli scale does not use scientific equipment to measure seismic waves, it has been very usefulįor understanding the damage caused by large earthquakes. Now known as the Modified Mercalli Intensity Scale. In 1902 and was modified by Harry Wood and Frank Neumann in 1931 to become what is The Mercalli scale was designed to do just that The original scale was invented by Giuseppe Mercalli The people who experienced the earthquake, and the amount of damage that occurred, The Mercalli ScaleĪnother way to measure the strength of an earthquake is to use the observations of Here's a table describing the magnitudes of earthquakes, their effects, and the estimated number of those earthquakes that occur each year. It was a magnitude 9.5 but largerįortunately, large earthquakes are much less common than small ones. Occurred along the subduction zone in Chile in 1960. Magnitude scales can be used to describe earthquakes so small that they are expressed Huh? Fortunately, most of the earthquakes that occur each year are much too small A magnitudeĨ earthquake releases as much energy as detonating 6 million tons of TNT. Numbers can add up, think of it in terms of the energy released by explosives: a magnitudeġ seismic wave releases as much energy as blowing up 6 ounces of TNT. (and about 32 times as much energy would be released). Would result in ten times the level of ground shaking as a magnitude 4 earthquake Using this scale, a magnitude 5 earthquake Recorded by a seismograph goes up ten times. What this means is that forĮach whole number you go up on the magnitude scale, the amplitude of the ground motion Magnitudes are based on a logarithmic scale (base 10). Magnitude estimates are about the same as Richter magnitudes for small to large earthquakes.īut only the moment magnitude scale is capable of measuring M8 (read "magnitude 8") It is derived from modeling recordings of the earthquake at multiple stations. Moment is a product of the distance a fault moved and the force required to move it. The moment magnitude scale is based on the total moment release of the earthquake. Today the moment magnitude scale, abbreviated M W, is preferred because it works over a wider range of earthquake sizes and is applicable Unfortunately, many scales, such as the Richter scale, do not provide accurate estimatesįor large magnitude earthquakes. That scale was specific to California earthquakesĪnd crust other scales, based on wave amplitudes and total earthquake duration, wereĭeveloped for use in other situations and they were designed to be consistent with Of the largest wave recorded on a specific type of seismometer and the distance between The first widely-used method, the Richter scale, was developed by Charles F.
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