The application of the statistics of extremes to seismic intensity values in Indiana allows the contouring of return periods for specific earthquake intensities. The contours show a region of low seismic activity running NW-SE through the center of the state; seismically, the quietest part of Indiana is Newton County. The highest seismic activity is recorded in the southwest corner of the state. The return periods for seismic events of intensity IV range from 20 to 45 years. Intensity VI events (slight damage) have return periods ranging from 80 to 240 years. Return periods for earthquakes rated intensity VII (moderate damage) range from 300 to 1,300 years. Higher intensities are not probable in Indiana, and therefore earthquake accelerations greater than 0.1 g are improbable.
Blakely, R. F., and Varma, M. M., 1976, The seismicity of Indiana described by return periods of earthquake intensities: Indiana Geological Survey Occasional Paper 16, 13 p., 10 figs., 4 tables.
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