Abstract: A detailed analysis is made for the earthquake data with focal depth since 1970 on the most regians of China. A hypothesis is poposed to explain the analysis results, which leads to a new concept on the overall situation of major earthquakes in China. It is suggested that major events of China are driven by the earthquakes with middle-depth ard deep-depth sources which occurred at four "hot spots" in 1970s, that are located at Jilin Province, Xindoukushi of Xinjiang, Taiwan, and Rikeze of Tibet. A process of earthquake chain composed of an active period (1970～1982), adjustment period (1983～1992) and waning period (1993～1999) has been completed. Althouth the last period is still under going, a new circle of the earthquake chain may be developing since the M 7.0 deep event of Jilin on April 8, 1999.

Key words: Focal depth, Major earthquake, Hypothesis of seismo-geothermics, Hot spot

摘要： 通过对中国绝大部分地区1970年以来有仪器测定震源深度的地震资料进行详细分析,提出了"地震地热说"的假说并对分析结果作出解释,得出了一个关于中国强震活动大形势的全新观念,认为中国强震活动受到地壳深部4个"热点"(吉林、新疆兴都库什、台湾和西藏日喀则等中深源震区)70年代强震活动的牵引,完成了一个由地震活动高潮期(1970～1982)、调整期(1983～1992)和消减期(1993～1999)所组成的地震链全过程。目前消减期尚未结束,但从1999年4月8日吉林7.0级深震开始,新的一轮地震链过程可能已在酝酿之中。

关键词: 震源深度, 强震活动, 地震地热说, 地震链