The Attica (N.Y.) earthquake of August 12, 1929 has been classified MM VIII. Recent detailed investigations indicate that the shock was of Intensity VII. These investigations include a review of scientific accounts, original reports and original newspaper accounts, studies of instrumental records, comparison with other shocks of Intensity VII and VIII, and interviews with local residents and witnesses to the disturbance. A detailed review of the Modified Mercalli Scale of Intensity and its application was part of the investigation.
None of the investigations support a classification of MM VIII. Original accounts of the earthquake indicate an Intensity no higher than VII. Magnitude estimates developed from diverse instrumental records correlate with an Intensity of VII or less. Comparison with the effects of Intensity VIII shocks clearly indicate that the 1929 Attica event was less intense, and comparison with other Intensity VII shocks support this contention. Interviews with local residents indicate that the Attica shock was MM VII.
It is concluded that the Attica earthquake of August 12, 1929 was an Intensity VII event and should be so classified in the record.