全球及主要构造带大震活动状态研究

Process and trend of great earthquakes in the globe and main zones

在定性分析全球、环太平洋地震带、低纬度环球剪切带和大三角地区(我国大陆西部及邻区)地震活动特征的基础上,使用Morlet小波变换对其周期成分进行了定量计算,并应用Nowcasting方法对各研究区域当前大震风险进行定量评估.结果显示,①全球大震活动显著周期为48.6年,8.5级以上地震的潜在危险性评分为0.91.2004年开始的大震活跃时段可能仍将持续,发生8.5级以上地震危险性较大.②环太平洋地震带地震活动显著周期为48.6年,其大震活动起伏特征与全球大体一致,8.5级以上地震的潜在危险性评分为0.91.2010年开始的8.5级以上地震活跃时段持续时间尚短,发生8.5级以上地震的危险性较大.③低纬度环球剪切带地震活动显著周期为33.1年,反映了该区8.0级以上地震的起伏活动,8.0级以上地震的潜在危险性评分为0.46.2004年开始的活跃时段可能趋于结束,未来10年左右该区发生8.0级以上地震的可能性较小.④大三角地区地震活动显著周期为23.4年,发生7.8级以上地震的潜在危险性评分为0.72.2001年以来该区7.8级以上地震活跃,其活动状态与20世纪前50年类似.23.4年的周期成分反映了20世纪前50年7.8级以上地震活动韵律特征.2015年兴都库什7.8级地震后,该区可能进入了7.8级以上地震相对平静时段,该时段可能持续7~12年,未来几年存在发生7.8级以上地震的可能,但危险性较小.

Based on the qualitative analysis of the seismicity characteristics in the globe,circum-Pacific seismic belt,low latitude circum-earth zone and the great triangle region(Western China continent and its surroundings),we calculated the periodic components using Morlet wavelet transform and evaluated the current earthquake risk by the Nowcasting method quantitatively.Some results are as follows:①The most significant periodic component of the global seismicity is 48.6-year and the earthquake potential score EPS of M W≥8.5 shocks is about 0.91.The active period of large earthquakes dating from 2004 may last and there is high risk of earthquakes with M W≥8.5.②The most significant period of the circum-Pacific seismic belt is 48.6-year and its temporal characteristics of large earthquakes are generally consistent with that of the globe.The earthquake potential score EPS of M W≥8.5 shocks is about 0.91.The duration time of the active period of M W≥8.5 earthquakes is still short and it will continue.The risk of shocks with M W≥8.5 is high.③The significant period of the low-latitude circum-earth zone is 33.1-year,which reflects the activity of earthquakes with M W≥8.0.And the EPS value for M W≥8.0 shocks is about 0.46.The active period beginning from 2004 may tend to end,and the risk of M W≥8.0 shocks in the next 10 years is lower.④The main periodic of the great triangle region is 23.4-year,which reveals the temporal characteristics of the M S≥7.8 earthquakes.The EPS value for M S≥7.8 events is 0.72.Since 2001,earthquakes with M S≥7.8 have been active,and the active state is similar to that in the first 50 years of the 20th century.After the 2015 Hindu Kush M S7.8 earthquake,the great triangle region may enter a relatively quiet period of M S≥7.8 earthquakes,which may last for 7~12 years.In the next few years,there is a possibility for M S≥7.8 shocks,but the risk is small.