# San Francisco Earthquake

Topics: Earthquake, Richter magnitude scale, Moment magnitude scale Pages: 12 (4159 words) Published: July 31, 2014
10/7/13
Quantitative Literacy Research Paper Topic with Sources Richter scale and examples
My topic for our research paper is going to be about the Richter scale; what it is and how it is used in the real world. Sources:
Title: Richter scale. Columbia Electronic Encyclopedia, 6th Edition, Database:Literary Reference Center
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Richter scale
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Richter scale (rĭk′tər), measure of the magnitude of seismic waves from an earthquake. Devised in 1935 by the American seismologist Charles F. Richter (1900–1985) and technically known as the local magnitude scale, it has been superseded by the moment magnitude scale, which was developed in the 1970s. The Richter scale is logarithmic; that is, the amplitude of the waves increases by powers of 10 in relation to the Richter magnitude numbers. The energy released in an earthquake can easily be approximated by an equation that includes this magnitude and the distance from the seismograph to the earthquake's epicenter. Numbers for the Richter scale range from 0 to 9, though no real upper limit exists. An earthquake whose magnitude is greater than 4.5 on this scale can cause damage to buildings and other structures; severe earthquakes have magnitudes greater than 7. Like ripples formed when a pebble is dropped into water, earthquake waves travel outward in all directions, gradually losing energy, with the intensity of earth movement and ground damage generally decreasing at greater distances from the earthquake focus. In addition, the nature of the underlying rock or soil affects ground movements. In order to give a rating to the effects of an earthquake in a particular place, the modified Mercalli scale, based on a scale developed by the Italian seismologist Giuseppe Mercalli, is often used. It measures an earthquake's intensity, the severity of an earthquake in terms of its effects on the inhabitants of an area, e.g., how much damage it causes to buildings. ________________________________________

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SIZING UP
How do we measure earthquakes? By the early 20th century, geologists knew that some earthquakes create visible rips across the earth's surface, which gives some indication of their force. But since most fault ruptures are entirely underground, we need other methods to size up and compare earthquakes. The earliest scales were called intensity scales, which typically assign Roman numerals to the severity of shaking at a given location. Intensity scales remain in use today: well-calibrated intensity values determined from accounts of earthquake effects help us study historical earthquakes and their effects within densely populated areas, for example. Following an earthquake in Virginia in 2011, over 140,000 people reported their accounts to the US Geological Survey's "Did You Feel It?" website. To size up an earthquake directly, one needs to record and dissect the waves it generates. Today, this is done with seismometers employing digital recording, but it wasn't always so. The first compact instrument capable of faithfully recording small local earthquakes was called a Wood-Anderson seismometer. When the ground shook, a mass suspended on a tense wire would rotate, directing a light onto photosensitive film. The image "drawn" by the light reflected the severity of the seismic waves passing through. In the early 1930s, Charles Francis Richter used these seismometers to develop the first magnitude scale - borrowing the word "magnitude" from astronomy. Richter's scale uses a logarithm to produce magnitude values that are easily tractable: each one unit increase in magnitude...