全球及中国大陆周边强震活动状态研究

Process and Trend of Large Earthquakes on the Earth and in the China Continent and its Surroundings

本文应用中国地震台网给出的全球大震目录,结合前人的研究,分析了1900年以来全球MS≥8.0巨大地震活动的时间变化与MS≥7.8大地震的空间迁移特征,同时还探讨了包含中国大陆西部及其周边的"大三角"地区MS≥7.8地震的发展态势。20世纪全球百年的大震活动表现为20世纪前半叶活动强而后半叶活动弱的前高后低的活动特点,而进入21世纪以来有增强活动显示,呈现百年左右起伏的长期变化。在这百年尺度的起伏之中还含有20年左右的韵律变化,主要显示为地中海—喜马拉雅地震带巨大地震的平静—活跃交替活动特征。根据大震活动的起伏特征和地中海—喜马拉雅地震带幕式活动特性,进入21世纪以来,地中海—喜马拉雅带巨震频繁发生,显示其地震活动显著增强的高活动态势。通过计算中国大陆西部及周边地区的不同震级地震的变异系数Cv发现,7.0级以上强震与7.8级以上大地震活动类型不同;采用对数正态分布对MS≥7.8地震活动进程进行拟合分析发现,到2015年的累积发震概率达0.80,到2020年的累积发震概率达0.89,表明与中国大陆关系紧密的"大三角区"已进入大地震活跃时段。

Using the global large earthquake catalog of China Earthquake Network,we analyzed the temporal characteristics of great earthquakes（MS≥8.0） and the spatial distribution of large earthquakes（MS≥7.8）.And the tendency of large earthquakes（MS≥7.8） in Western China continent and its surroundings was also discussed.It seems that the temporal characteristics of great earthquakes（MS≥8.0） on the earth has period of a hundred years,and the seismicity is higher in the former 50 years and lower in the latter 50 years and it comes to high in the new century.And there is rhythm activity of 20 years in the hundred years period,reflected mainly in the large earthquake cyclic process of activity and quiescence alternatively in Med-Himalayan seismic zones.Since the new century,large earthquakes in Med-Himalayan seismic zones occurred frequently,showing a high activity trend based on the characteristics of great earthquakes cyclic process of the globe.By calculating the variance-coefficient of different magnitude in Western China continent and its surroundings,we found that seismic process with different magnitude has different activity type.By using the log normal cumulative distribution function fitting the seismic processes with different magnitude,we found that the probabilities of great earthquake（MS≥7.8） in Western China continent and its surroundings by 2015 will be 0.80 and will be 0.89 by 2015,which means large earthquakes in the triangular region would occur frequently.