During the process of preparation and occurrence of a large earthquake, the stress-strain state along the fault zone has close relation with the weak seismicity around the fault zone. The seismic energy release near the fault zone before an earthquake can better reflect the dynamic process of earthquake preparation. Thus, in this paper, the method of natural orthogonal function expansion has been adopted to discuss the time variation about the energy field of the seismic activity along the Longmenshan fault zone before the Wenchuan MS8.0 earthquake, 2008. The results show that evident short-term rise changes appeared in the time factors of the typical field corresponding to several key eigenvalues of the energy field along the Longmenshan fault zone before the Wenchuan earthquake, probably being the short-term anomaly message for this earthquake. Through contrastive analysis of earthquake examples such as the1976 Tangshan earthquake, the authors think that the study of time variation of energy field of seismicity along active fault zone will be helpful for conducting intentional and intensive earthquake monitoring and forecast in active fault regions with high seismic risk based on medium- and long-term earthquake trend judgment.

在大地震的孕育和发生过程中，沿断裂带的应力—应变状态与断裂带周围微震活动有着密切的关系。震前沿构造断裂带附近地震活动能量释放更能反映地震孕育的动态过程。因此，本文采用自然正交函数展开方法，讨论了2008年汶川8.0级地震前沿龙门山断裂带地震活动能量场的时间变化，结果表明，在汶川8.0级地震前，沿龙门山断裂带能量场的几个主要特征值对应的典型场的时间因子出现非常明显的短期上升变化，可能是该次地震短期异常信息。通过对比分析1976年唐山地震等震例，笔者认为，研究沿活动断裂带地震活动能量场的时间变化，可以对地震中长期判断有较大危险性的活动断裂区进行有目的的重点监测和预报。