Great earthquakes 1896–1903

Abstract

Trace amplitudes of surface wave maxima recorded by undamped Milne seismographs can be used to determine the magnitude of large shallow earthquakes. Magnification of these instruments for maxima of distant shocks was about 5. Station corrections are calculated. Milne's reports and other information are used to find the unified magnitude m and energy E of great earthquakes 1896 to 1903. From 1896 to 1906 the average annual energy release was about 2 X 1025 ergs contrasted with about 0.6 X 1025 ergs from 1907 to 1955, The greatest energy release in any calendar year since 1896 was 5 X 1025 ergs in 1897 that included the great Indian earthquake, one shock off northeast Honshu, and two in the Philippine Islands, all with m = 8± and E about 1025 ergs. The same order of energy was released in at least one of the Sanriku earthquakes of 1896. The Yakutat Bay shocks of 1899 and 1900 included one with m of 7.9± and two with 7¾±. The greatest shock, 1896 to 1955, was possibly the one off Colombia‐Ecuador on January 31, 1906, m = 8.1 to 8.2, E = 2 X 1025 ± ergs. The smallest energy release from shallow shocks in any calendar year since 1896 was about 1024 ergs in 1954 (when in no shallow shock m exceeded 7.2, though one shock at a depth of nearly 200 km had m = 7.4).