Abstract
In this paper, the seismicity indexes of global earthquakesM ≥ 6 during 1964–1983 were calculated, using data of ISC and USGS. The authors suggested a method suitable to make a set of regression formulas betweenm bandM s. Calculation showed that the level of global seismicity of shallow earthquakes during the years 1964–1965, 1968, 1971, 1975–1976 was higher than normal, especially the peak for the years 1975–1976 was more conspicuous. The year 1984 took the place of the year 1954 in the 20th century as the year of lowest global shallow focus seismicity. According to the actual value ofA(b) calculated, the level of deep focus seismicity reached the highest point in 1971 and dropped to the lowest point in 1977. In the time interval of 1977–1983 the global shallow focus seismicity decreased continuously whereas the deep focus seismicity increased with fluctuations.
Published Version
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