【摘要】 本文研究了1976年11月7日、12月13日宁蒗—盐源6.7级和6.4级地震前,震中周围150公里范围内的小震活动。发现震前从1973年底开始的两年多时间内,M_L~*≥3.0级地震围成空区,震前4个月,震源区附近小震活动加强,致使空区消失,最后在空区的一端发生主震。同时还伴随有M_L≥2.3级地震的月频度由高值——低值——再回升到高值;b值由低值到高值;月应变释放速率震前呈明显的加速及Σ(t)值出现高值等异常现象。文中用突起点模式的思路对上述异常特征作了解释。更多还原

【Abstract】 This paper deals with the small earthquake activities ranging 150 km around the epicenters before both Nov.7,and Dec.13,1976 Ninglong-Yanyuan Earthquakes (M = 6.7and 6.4,respectively).It has been found out that in more than two years before the earthquake since the end of 1973 a seismic gap was formed by events of ML≥3.0; that in four months before the mainshock the small earthquake activities increased near the hypocentcr,resulting the disappearance of the gap; and that the main shock occurred finally at one end of the gap.Accompanied,at the same time,were some anomalous phenomena such as the monthly frequency values of ML≥2.3 events varying with a higher-lower-again higher pattern; b values increasing; the monthly strain release rates obviously speeding up; and ε(t) values showing peaks.The above anomalous features were explained by the concept of the "Asperity" model in this paper.events with magnitude larger than 4 using Ms更多还原