丽江7.0级地震预报判据及地震学主要异常

PREDICTION CRITERIA OF LIJIANG EARTHQUAKE WITH M=7. 0 AND MAIN ANOMALIES OF SEISMOLOGY

介绍了丽江7．0级地震烈度、地震地质及中、短、临预报简况。中、短期预报准确，短临预报向云南省政府打了招呼。重点讨论中短期预报中使用的主要地震学判推。指出丽江7．0级地震前，中甸一下关地震带6级地震时间间隔已达19a，超过历史极限。该带北段1983～1993年10a内无M≥5地震；震中周围形成一长约150km空段，199O～1995年6a内震源区（△≤60km范围）M≥3．5地震出现平静异常。总之，震源周围地区小震及中强震平静是丽江7.0级地震主要特征。1995年12月至1996年1月的短临阶段，震源区外围的永胜、洱源等震中距77～12okm的地震窗口，出现小震频度增高或前兆震群。根据震源区内定点前兆数量少、异常幅度小等特征，作者提出中短期阶段，震源区介质刚度比源外区大，因此应变小、外围地区则相反的看法。

In this paper the brief information concerning seismic intensity of Lijiang earthquake with M=7. 0, seismogeology, the medium- and short-term and impending earthquake predictions were introduced. Medium- and short term predictions were correct and impending prediction was notified to the provincial government. The main seismological criteria used in medium- and short term predictions were emphatically discussed. It is pointed out that before Lijiang earthquake with M=7. 0, the intervals of M = 6 earthquakes in Zhongdian-Xiaguan seismic belt reached 19 years that surpassed historical limitation; there was not any earthquake with M ≥5， in 1983~1993 along the northern segment of the belt; a gap segment of 150 km in length was formed around the epicenter; and quiescent anornaly with M≥3. 5 earthquakes appeared within 6 years of 1990~1995 in source area (△≤60 km).Generally，the quiescence of small and moderate earthquakes around the source area is the main characteristics of Lijiang M =7. 0 earthquake. During the short and impending periods from Dec. 1995 to Jan. 1996, in the window of Yongsheng and Eryuan region，77~120 km outslde the source area, increase of small earthquake frequency or foreshock swarms appeared, According to the characteristics with few of anomalies and small amplitude at the fixed points, the authors presented the opinion that rigidity of the media within source area is bigger than that in the region outside source area during the medium- and short term periods, so the strain within source area is smaller, but bigger outside the source.