1998年全球地震活动综述

Overview of the Global Seismicity in 1998

１９９８年第四季度，全球共发生６级以上地震１１次，其中１１月２９日塞兰海地震为７．７级，地震频度低而强度高。１９９６～１９９８年，全球地震活动呈逐年下降趋势。１９９８年全年共发生６级以上地震（包括深震）７８次，其中有２次７．７级以上大地震。本年度６级以上浅源地震频数继续减少，全年只有６４次。１９９６～１９９８年，Ⅰ带和Ⅱ带地震活动逐年减弱；亚欧带有起伏，１９９７年最高，１９９８年回落。

Altogether there were 11 earthquakes of M ≥6 occurring in the world in the fourth quarter of 1998 The Ceram Sea earthquake was of M S 7 7 So the frequency was low and the magmitude was high During the years from 1996 to 1998,the global seismicity had been decreasing year by yaer Altogether there were 78 earthquakes of M ≥6(including deep focus earthquakes)occurring in the world in 1998,including 2 large earthquakes of M ≥7 7 The frequency of shallow focus earthquakes of M ≥6 remained decreasing,only 64 of them occurred in 1998 During the years from 1996 to 1998,the seismicity in belt Ⅰ and belt Ⅱ had been decreasing year by year;the seismicity of the Eurasian seismic belt undulated,with the highest value in 1997 and a fallback in 1998 The seismicity in the Chinese mainland returned to the level of the years of 1993 and 1994