全球地震活动性的定量研究(二)——1964至1983年全球6级以上地震活动的分析

本文利用 ISC 和 USGS 的6级以上地震资料,计算了1964——1983年共20年的全球地震活动性指数.作者提出一种求 Ms-mb 回归线的方法,得出一组换算公式.计算表明,1964——1965,1968,1971,1975——1976各年全球浅源地震活动性水平较高,其中以1975——1976年的峰期最为显著.1984年已取代1954年成为20世纪中浅震水平的最低年份.按实际计算值,深震水平以1971年为最高,以1977年为最低.1977——1983年,全球浅震活动水平持续下降,深震活动水平长趋势上升. 

QUANTITATIVE STUDIES OF GLOBAL SEISMICITY (2)--DISCUSSION ON GLOBAL EARTHQUAKES (M6) FROM 1964 TO 1983

In this paper, the seismicity indexes of global earthquakes (M6) during 1964-1983 are calculated, using data of ISC and USGS. The authors suggest a method suitable for working out a set of regression formulas between mb and Ms. Calculation shows that the seismicity level of global shallow earthquakes during the years of 1964-1965, 1968, 1971, 1975-1976 is higher than normal, and especially more conspicuous is the peak for the years 1975-1976. The year 1984 has taken the place of 1954 in the 20th century as the year of lowest level in global shallow seismicity. According to the actual value of A(b) calculated, the deep seismicity level reaches the highest point in 1971 and drops to the lowest point in 1977. In the time interval of 1977-1983 the global shallow seismicty decreases continuously while the deep seismicity increases with fluctuations.