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Data Center and National Earthquake Information Center report all intensities on the Modified Mercalli Intensity Scale of 1931. 1 The abridged version of this scale is given below. Values in parentheses are equivalent intensities in the Rossi-Forel Scale, still used by some countries to evaluate earthquake effects. I. Not felt except by a very few under specially favorable circumstances. (I) II. Felt only by a few persons at rest, especially on upper floors of buildings. Delicately suspended objects may swing. (I to II) III. Felt quite noticeably indoors, especially on upper floors of buildings, but many people do not recognize it as an earthquake. Standing motorcars may rock slightly. Vibration like passing of truck. Duration estimated. (Ill)
Coffman et al. (Sun,) studied this question.