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The following is the correct version of an abstract published in Seismological Research Letters58, 104–105.

QUANTIFICATION OF DIFFERENCES IN ATTENUATION OF MODIFIED MERCALLI INTENSITY BETWEEN EASTERN AND WESTERN NORTH AMERICA - PRELIMINARY RESULTS

SIBOL, M.S. and BOLLINGER, G.A., Seismological Observatory, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061

Most studies of the attenuation of Modified Mercalli Intensity (MMI) develop models between MMI and distance using isoseismal maps. Distances are determined to be either the average epicentral distance to an isoseismal contour (e.g. Anderson, 1978), or the area within a given contour is measured and the radius of a circle of equivalent radius is used (e.g. Howell and Schultz, 1975). This study employs individual epicenter to MMI report site distances (R) from over 100 earthquakes (ImaxVI) in the U.S. and southern Canada (south of 55°N). Such a parameterization allows for a quantitative estimate of the mean response and the specification of error for the fall-off of intensity with distance; thereby making direct regional comparisons possible.

The data were then examined in two ways. Events of special interest (e.g. 1886 Charleston, SC; 1906 San Francisco, CA, etc.) were modelled as:
The models were limited to R ≤ 500 km due to incomplete reporting at the lower intensity levels (generally MMI < III). Models were derived for individual events and for regional composites. The regional composite model for eastern North America (ENA) shows a clear separation from that for western North America (WNA). For example, the separation is . . .

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