丽江7.0级地震短临异常特征及震源硬化模型

重点讨论了丽江地震短临预报中识别继承性异常、继承性新异常及新异常的形态特征。同时讨论了判断丽江地震进入短临阶段的判据,如中期趋势异常的结束,巨变异常及异常同步转折等特征。最后,在讨论短临异常时空演化的基础上,结合震中区小震活动的异常平静,短临阶段定点前兆由外向震中迁移,异常外围幅度大、数量多等事实,作者提出了新的震源孕青模型——震源硬化模型。按此模型预测,震源区（余震展布区或地表宏观裂缝展布区）在中短期阶段应出现中小地震的异常平静,元或很少有定点前兆异常显示,但当强震孕育发展到破裂成核时——不可逆失稳阶段,某些地震震源区可能会出现明显的宏观破裂,即地表可见喷沙冒水或前震活动。

CHARACTERISTICS OF SHORT-TERM AND IMPENDING ANOMALIES FOR LIJIANG EARTHQUAKE WITH M=7.0 AND FOCAL HARDENING MODEL

During the short-term and impending predictions of Lijiang earthquake ,recognition of the characteristics of successional anomalies , new successional anomalies and new anoma­lies is discussed. Meanwhile, the criteria of anomalies entering the short-term and impend­ing phase,such as the ending of the medium-term anomalies,dramatic anomalies and syn chronous turning, of Lijiang earthquake is also discussed. Finally, based on discussion of time-space evolution of the short-term and impending anomalies, the author has presented a new focal seismogenic model-the focal hardening model.combining the facts mentioned in other papers ,such as anomalous quiescence of small earthquakes within epicentral area, the station-based precursory anomalies migrating from the periphery towards the epicen­ter, anomalies in the periphery having large amplitudes and quantity and so on. According to the model, the anomalous quiescence of small earthquakes should appear during the medium-and short-term phase within the epicentral area (aftershock-distributed or macro­fissure-distributed areas), and no or a few station-based precursory anomalies appear. However, when a strong earthquake is developed towards nucleation of fractures, that is the unreversible unstable phase, distinct macro-fissures probably appear in some focal ar­eas,namely sand-eruption and foreshock activity may appear.