Earthquake perceptibility P(l/m) in the Central and Eastern United States is defined as the joint probability that a point site perceives ground motion at least at intensity I in conjunction with an earthquake occurrence specifically of magnitude m.

Regional seismicity expressed in the catalogs of Meyers and von Hake (1976) and Nuttli (1979) is examined in terms of magnitude frequency using Gumbel's asymptotic extreme value distribution with an upper bound to magnitude (Gumbel III). The large “rogue” earthquakes associated particularly with the New Madrid seismic zone lead to upper bounded macroseismic body-wave magnitudes with large uncertainties around mb734; but this approximate value is not contradicted by deterministic arguments.

Examination of the regional earthquake perceptibility curves then shows a maximum perceptibility at several intensity levels for earthquakes in a relatively narrow band of magnitudes around mb612. For the Central and Eastern United States, this most perceptible magnitude is the earthquake which is most likely to be felt at any site, and this might be used in aseismic engineering design of noncritical structures. Extension of the analysis to integrated perceptibility then facilitates calculation of intensity expectation at any site.

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