Earthquake 101 Lesson 4 1 
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Newspapers for this educational program provided by Lesson 4: What Size Was That Earthquake? Scientists use magnitude to talk about the size of an earthquake. Magnitude is a relative scale that describes the intensity of an earthquake. Scientists do not get a specific magnitude number directly from their seismic instrument; instead, they take the information recorded from the seismic waves and use mathematical formulas to estimate the magnitude. Since scientists can measure different seismic waves or parts of waves and make different correlations to their relationships, there are many different magnitude scales used. The most famous of these, the Richter scale, is commonly misused with the public. Today’s scientists do not use the Richter magnitude, but the basic concept is broadly used for several magnitude scales. These scales estimate magnitude by measuring the strength of the seismic signal recorded at a seismic station and adjusting it for distance from the earthquake Magnitude measurements for a single earthquake rarely agree, so how do we know which one is correct? They all are; they are just using different information to estimate the magnitude. An earthquake reported with different magnitudes is common and should not be considered terribly significant. Magnitude’s Math: The magnitude scale is logarithmic, so for every increase of one magnitude unit, there is a tentimes increase in the amplitude of the seismic wave. This means that the shaking associated with a magnitude 7 is 10×10×10×10, or 10,000 times greater than a magnitude 3 earthquake. For each magnitude unit increase, there is about 32 times more energy released. Think about throwing a rock into a still pond. As the waves travel away from where the rock hit the water, they get smaller and smaller; the same applies to earthquakes. The farther away from the epicenter of the earthquake you are, the less you will feel it. For this reason, we could not feel the effects of Japan’s recent earthquake. Further study: How much more energy is released in a magnitude 9 earthquake than the largest earthquake to occur in Oklahoma, estimated at a magnitude 5.5? *Answer: 32x32x32x√32=185363
Object Description
Okla State Agency 
Geological Survey, Oklahoma 
Title  Earthquake 2011, Lesson 4 
Alternative title  Earthquake 101 
Authors 
Newspapers in Education The Oklahoman. Oklahoma City Geological Foundation. Oklahoma Geological Survey. 
Publication type 
Student Materials 
Purpose  Lesson 4 What Size Was That Earthquake? Scientists use magnitude to talk about the size of an earthquake. Magnitude is a relative scale that describes the intensity of an earthquake. 
Notes  1 of 4 parts 
OkDocs Class#  G500.8 E12o 2011 Lesson 4 
For all parts click  G500.8 E12o 2011 
Digital Format  PDF, Adobe Reader required 
ODL electronic copy  Downloaded from agency website: http://s3.amazonaws.com/content.newsok.com/newsok/images/NIE/nie_docs/Survey,%20Lesson%204,%20Final.pdf 
Rights and Permissions  This Oklahoma government publication is provided for educational purposes under U.S. copyright law. Other usage requires permission of copyright holders. 
Language  English 
Date created  20120409 
Date modified  20120409 
Description
Title  Earthquake 101 Lesson 4 1 
Full text  Newspapers for this educational program provided by Lesson 4: What Size Was That Earthquake? Scientists use magnitude to talk about the size of an earthquake. Magnitude is a relative scale that describes the intensity of an earthquake. Scientists do not get a specific magnitude number directly from their seismic instrument; instead, they take the information recorded from the seismic waves and use mathematical formulas to estimate the magnitude. Since scientists can measure different seismic waves or parts of waves and make different correlations to their relationships, there are many different magnitude scales used. The most famous of these, the Richter scale, is commonly misused with the public. Today’s scientists do not use the Richter magnitude, but the basic concept is broadly used for several magnitude scales. These scales estimate magnitude by measuring the strength of the seismic signal recorded at a seismic station and adjusting it for distance from the earthquake Magnitude measurements for a single earthquake rarely agree, so how do we know which one is correct? They all are; they are just using different information to estimate the magnitude. An earthquake reported with different magnitudes is common and should not be considered terribly significant. Magnitude’s Math: The magnitude scale is logarithmic, so for every increase of one magnitude unit, there is a tentimes increase in the amplitude of the seismic wave. This means that the shaking associated with a magnitude 7 is 10×10×10×10, or 10,000 times greater than a magnitude 3 earthquake. For each magnitude unit increase, there is about 32 times more energy released. Think about throwing a rock into a still pond. As the waves travel away from where the rock hit the water, they get smaller and smaller; the same applies to earthquakes. The farther away from the epicenter of the earthquake you are, the less you will feel it. For this reason, we could not feel the effects of Japan’s recent earthquake. Further study: How much more energy is released in a magnitude 9 earthquake than the largest earthquake to occur in Oklahoma, estimated at a magnitude 5.5? *Answer: 32x32x32x√32=185363 
Date created  20120409 
Date modified  20120409 