Information on Earthquake Intensity:

• Approaches to measurement of earthquake magnitude
• seismograms measure magnitude in different ways
• methods are based on measurements of different seismic waves 
• body waves, surface waves, or other methods
• Earthquake magnitude is reported using the Richter scale
• the Richter scale is a logarithmic measure of earthquake size
• magnitude 5 represents 10 times more shaking than magnitude 4
• the energy release is 32 times greater
• the Richter scale focuses on description of the earthquake source
• Shakemaps are based on modified Mercalli intensity
• the Mercalli scale is based on the intensity of an earthquake
• intensities are determined from the effects of the event 
• effects include experiences and damage reports

• Shakemaps focus on measurement of ground motion
• this measure is more meaningful to the public
• a common scale for shakemaps is modified Mercalli intensity
• background information on the scale is given here
• details of the scale are presented in a separate table and here
• "Did you feel it?" 
• intensity maps compiled from reports of damage
• information on these community internet intensity maps is given here
• Shakemaps colored according to the modified Mercalli scale
• South: instrumental intensity maps
• predictive intensity maps of historical events
• North: estimated intensity maps for the San Francisco Bay Area

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Department of Geological Sciences, 
1001 E. Tenth Street, Bloomington, IN 47405-1403
Phone: (812) 855-5582  Last updated: 1 October 2002
Comments: simon@indiana.edu
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