汶川8．0级地震前地震趋势分析意见的回顾

Retrospection on the Conclusions of Earthquake Tendency Forecasts before the Wenchuan M8.0 Earthquake

该文在系统整理自2001年昆仑山口西8.1级地震到汶川8.0级地震前年度地震趋势预测中提出的地震活动异常和分析意见的基础上,研究汶川地震未能做出中长期预测的原因。结果表明:2001年昆仑山口西8.1级地震发生后,判定中国大陆处于强震连发阶段,仍有发生8级大震危险,但此后的2002—2007年中国大陆周边接连发生大震,而内部连续6年的7级地震平静,以及中国大陆5、6级地震相继出现的显著平静,是导致2006年以后对中国大陆地震活动水平预测明显偏低的原因。南北地震带中段一直是作为近几年可能发生强震的危险地区,但2007年云南宁洱6.4级地震后,对西南地区强震危险的紧迫性估计不足。而汶川地震所在的龙门山地震带历史上没有7级以上地震记录,也是该地震带未作为近几年地震重点危险区的原因之一。

The reason that the failure to forecast the Wenchuan M8.0 earthquake is studied, based on systematically collecting the seismicity anomalies and their analysis results from the yearly earthquake tendency forecasts between the 2001 west Kunlunshan M8. 1 earthquake and the 2008 Wenchuan M8. 0 earthquake. The results show that after the 2001 west Kunlunshan 8.1 earthquake, the earthquake tendency estimation for China's Mainland was that strong earthquakes are in active stage and strong earthquakes of magnitude 8 were anticipated, but the phenomena that many large earthquake occurred around China's Mainland, while there were a 6-year period of M7 earthquake quietude and a obvious quietude of M5 and M6 earthquakes during 2002-2007 in China's Mainland, caused the distinctly lower forecast estimation of earthquake tendency in China's Mainland after 2006. The middle part in the North-South seismic belt has been designated a strong earthquake risk area in recent years, but, the estimation of the risk degree in southeastern China was insufficient after the Ning＇er M6. 4 earthquake in Yunnan in 2007. There is no recorded earthquake with M〉7 in the Longmenshan seismic belt, which is one of the reasons that this seismic belt was not considered an important seismic risk area in recent years.