 Did
you feel an earthquake?
The U.S. Geological Survey compiles felt reports from thousands
of volunteer earthquake observers at its "Community
Internet Intensity Map" service. This web-based research
system is intended to tap the abundant information available about
earthquakes from the people who actually experience them. By taking
advantage of the vast numbers of Internet users, the seismological
research community can get a rapid and complete description of what
people experienced, the effects of the earthquake, and the extent
of damage surrounding earthquakes in the U.S. The automated system
compiles information gleaned from an on-line
seismic intensity survey which compiles information about specific
observations related to the extent of ground shaking and damage
at hundreds of sites. The qualitative observations are converted
to an estimate of ground shaking based on the 12-point Modified
Mercalli Intensity
Scale. Usually the highest intensities are measured near the earthquake
epicenter and lower intensities are measured farther away, as illustrated
in this example from the recent April 29, 2003 earthquake centered
near Fort Payne, Alabama. The Community Internet Intensity Map (CIIM)
summarizes the questionnaire responses provided by Internet users
and assigns an average intensity number to each community from which
the USGS receives a CIIM questionnaire. A CIIM Map is made and updated
every few minutes following a significant earthquake and then less
frequently as additional data is received. Areas for which data
have been received are color-coded according to the intensity scale
below the map; those shown in gray represent areas for which no
data have yet been received. At first only a few areas will have
intensities assigned, but over time others will be assigned as data
come in. Individual zones may change color as a new consensus is
reached. This new service provides useful information both to scientists
and emergency responders, and takes advantage of the rapid communication
available through the internet.
Material adapted from U.S. Geological Survey's Community Internet
Intensity Map website |
