Discussion of paper by V. I. Keylis-Borok and L. N. Malinovskaya, ‘One regularity in the occurrence of strong earthquakes’

The observation of general increase in the seismic activity of an area for an extended period before a major event has been reported on a number of occasions. Well-known examples are those associated with the great earthquakes in Japan in 1891 and 1923. The authors have made a creditable effort to convert this rather indefinite and elusive phenomenon into a precisely definable one. It is important that they confirm the necessity of considering a very extensive region including the center of the approaching event. It is very rarely true that a major event is preceded by increasing activity in its immediate vicinity. Such a claim was made by Davison for the Japanese occurrence of 1891; critical reading suggests that he overlooked many details and misinterpreted the data.