A large number of Modified Mercalli Intensity isoseismal maps for earthquakes which have occurred in the United States have been analyzed to find the distribution of distances (R) between the epicenter and isoseismal contours. The data include most of the maps in the series “United States Earthquakes,” and a smaller number of maps from other sources. Where the data permit, best fitting parameters have been found in a Gaussian distribution function to fit the observed distributions of log10R for each combination of epicentral intensity and the intensity bounded by the contour; the data do not contradict this assumed Gaussian shape. The standard deviation of log10R is at best 0.2 for well-determined distributions; it is typically 0.3, implying that over an order of magnitude range of distances is present in the data.

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