In lieu of an abstract, here is a brief excerpt of the content:

Richter Magnitude Scale The Mercalli scale may be used to describe an earthquake either at its epicenter or at any point in the area into which the effects of the earthquake extend. The Richter scale, devised in 1935 byAmerican seismologist Charles F. Richter, measures the intensity ofthe quake at its epicenter. Both the Mercalli and the Richter scales measure in numbers, with the greatest damage being assigned the highest number. The Richter measurement is made by instruments called seismometers, which are located at recording stations all over the world. David Stewart and Ray Knox are contemporary scientists who have studied and written extensively about the New Madrid Seismic Zone. They point out that every added 1.0 unit on the Richter scale represents thirty-two times the difference in energy released by a quake. Thus, a 6.0 quake on the Richter scale is thirty-two times stronger than one measuring 5.0. Every 0.2 increase in the scale doubles the intensity ofthe quake.Thus, a 5.2 quake releases twice the energy as does one measuring 5.0. Stewart also points out that the Richter scale is in a constantly developing state. The original scale as it was devised by Richter is rarely used by anyone today. In his book Damages and Losses from Future New Madrid Earthquakes, Stewart points out the discrepancies that occur in measuring magnitudes. There are five different ways to calculate magnitude from available instruments , and scientists generally report to the media the highest number recorded. Scientists have agreed on adjectives to define the way we can consider the numbers on the Richter scale. 99 100 Appendix 2 Adjectives to Describe Richter Numbers Great Major Strong Moderate Light Minor Very Minor 8.0 or larger 7.0 - 7.9 6.0 - 6.9 5.0 - 5.9 4.0 - 4.9 3.0 - 3.9 2.9 or less It may be important to point out again here that the Richter measurements are not always consistent. Machines may vary by 0.2 of a point on the Richter scale, and this fact takes on extra significance when we recognize that an increase of 0.2 in the scale doubles the intensity ofthe quake. Comparison of Earthquake Magnitude and Intensity Richter Magnitude 8.0-8.9 7.0-7.9 6.0-6.9 5.0-5.9 4.0-4.9 3.0-3.9 Below 3.0 Mercalli Intensity XI-XII IX-X VII-VIII VI-VII N-V II-III I Note: Though there is no upper limit to the Richter magnitude scale. 8.9 is the largest number ever reported. Note: The latter chart is adapted from one used by William Atkinson in The Next New Madrid Earthquake: A Survival Guide for the Midwest (Carbondale: Southern Illinois University Press. 1989). page 37. ...

Share