INTERNATIONAL COLLECTION OF MACROSEISMIC DATA BY THE COMMUNITY INTERNET INTENSITY MAP (CIIM) PROCEDURE

DEWEY, J.W., Wald, D.J., and Quitoriano, V., U.S. Geological Survey, MS966, Denver, Colorado, 80225-0046, USA, dewey@usgs.gov.

The U.S. Geological Survey Community Internet Intensity Map (CIIM) is an automatic web-based system for rapidly generating seismic intensity maps based on shaking and damage reports collected from Internet users immediately following earthquakes. Initially developed for the United States, the CIIM system has been tested in an international mode since December 2003. For locations outside the United States, macroseismic data are collected for individual cities. Data from a city are grouped, an average intensity value is automatically computed on the basis of the data, and the intensity is represented on a map as a color-coded circle. The data collection and intensity assignment differ substantially from what would be done in a traditional intensity survey. Strengths of the CIIM procedure are that the procedure is rapid and that intensities are globally assigned by a uniform procedure. Limitations of the current international CIIM procedure are that macroseismic observations are collected only in English from people with access to the Internet, that a given CIIM intensity number may correspond to a different level of damage than the same number in the local intensity scale, and that the globally uniform procedure cannot account for variations in damage due to differences in construction practice. We illustrate these strengths and limitations with case histories from specific earthquakes, including those in Sumatra (2004 December 26 and 2005 March 28), Kyushu (2005 March 20), and the West Indies (2004, November 21). CIIM can be found online at “http://earthquake.usgs.gov” under “Did You Feel It?”.