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本文通过对宁蒗及邻区1975年以来所发生的N_L≥4.7中强地震在时空分布和震前地震活动图象的分析,发现该区地震活动主要受NE向的木里——宁蒗——剑川断裂的控制;具有在中甸——洱源与木里——华坪来回跃迁的特点,为NE—SW向迁移的现象。震前M_L≥3.0的地震频度在三个月内小于或等于四次的背景下突然增强;缺震出现两个月以上低于2.96/月;应变将放能量低于0.48×10~6焦耳1/2二至八个月后,在几天至一个月内应变释放能量≥0.6×10~6焦耳1/2;b值低于0.84;断层面总面积≥2个月低于7.27焦耳2/3后出现1—2个月高峰值等短临异常指标。并通过定量的分析,认为宁蒗及邻区中强震前地震活动具有正常——偏低——增强———发震的特征。
Based on the analysis of temporal and spatial distribution and seismic activity images of N_L≥4.7 moderate earthquakes that occurred in Ninglang and its neighboring areas since 1975, it is found that the seismic activity in this area is mainly affected by the NE direction of Muli - Ningtao - - The control of Jianchuan fault; It has the characteristics of the transition between Zhongdian-Eryuan and Muli-Huaping, and it is the phenomenon of NE-SW migration. Earthquakes with an M_L≥3.0 before the earthquake suddenly intensified in the background of less than or equal to four times in three months; the failure occurred more than two months below 2.96 / month; and the strain reduced the energy below 0.48 × 10-6 J 1/2 Two to eight months after a few days to one month strain release energy ≥ 0.6 × 10 ~ 6 Joules 1/2; b value of less than 0.84; total fault area ≥ 2 months less than 7.27 J 2 / 3 1-2 months after the emergence of short-term peak anomalies and other indicators. Through quantitative analysis, it is considered that the seismic activity before mid-strong earthquakes in Ninglang and its adjacent areas has the characteristics of normal-low-enhanced-seismogenic.