中国大陆西部及邻区板内8级大地震活动过程和趋势预测初步研究

RESEARCH ON PROCESS AND TENDENCY PREDICTION OF GREAT EARTHQUAKES (M_s≥8) IN WESTERN CHINA CONTINENT AND ITS SURROUNDINGS

中国大陆西部及邻区是全球 8级大地震最为活跃的地区之一。自 180 0年以来该区板内 8级大地震共发生了 16次 ,2 0 0 1年昆仑山口西 8.1级大地震 (36 .1°N ,90 .9°E)是在 195 7年蒙古 8.3级大地震之后 4 4a发生的。研究表明该区 8级大地震的活动过程可能存在相对平静 (1812— 190 2年 )和相对活跃 (190 3— 195 7年 )交替的幕式或轮回过程的性质。 195 7年蒙古地震之后可能是一次新的轮回开始 ,2 0 0 1年昆仑山口西地震是新轮回的第二次地震 ,按照轮回过程中事件发生频度是时间的指数函数关系的假定 ,该区下一次 8级大地震可能约在 2 0 2 6年发生。如果假定该过程相当接近泊松过程。那么 ,在 2 0 0 5 ,2 0 10年和 2 0 15年前至少发生一次 8级大地震的泊松概率 ,分别是 0 .2 9,0 .5 3和 0 .70。

Western China continent and its surroundings is one of the most active seismic area in the world, where have occurred 16 great earthquakes with magnitude 8.0 since 1800 A.D. The recent great West of Kunlun Mountain Pass earthquake (36.1°N,90.9°E;M_s=8.1) of Nov. 14, 2001 occurred in the western China continent after 44 a of quiescence since the great Mongolia earthquake (M_s=8.3) occurred in 1957. The researches in this paper show that there is an episodic or cyclic seismic process of activity and quiescence alternatively, the 1957 Mongolia earthquake may be a beginning of new cycle in the studied area,and the great West of Kunlun Mountain Pass earthquake was the second event in the new cycle. Supposing temporal changes of the cumulative number of event in a cycle follow an exponential function, the next great earthquake (M_s≥8) in Western China continent and its surroundings will occur in 2026. If the process is approximately the Poisson one, the occurrence probabilities of the great earthquake (M_s≥8) in Western China continent and its surroundings before 2005, 2010 and 2015 will be 0.29, 0.53 and 0.70 respectively.