系统梳理2020年1月2日云南宁蒗MS 5.5地震前出现的地震活动和地球物理观测等异常，结果如下：①地震活动：震前存在地震平静、地震高频、地震空区等异常；②地球物理观测：震中200 km范围内存在多项地球物理异常，主要为钻孔应变、地电场方位角、地电阻率、水位等中短期异常。对宁蒗MS 5.5地震序列进行分析，可知主震震源机制显示宁蒗地震的断层类型以正断层为主；余震活动丰富，存在分段特征，宁蒗地震序列中的主震与最大余震震级相差0.9，主震释放能量占序列的93.53%，因此该地震序列为主—余型。综合分析认为，此次地震前地震活动中短期异常较为突出，地球物理观测异常相对丰富，异常均分布在滇西北及周边地区，对宁蒗地震的发生具有一定指示意义。
The anomalies of seismicity and geophysical observation before the Ninglang MS 5.5 earthquake are systematically summarized. The main results are as follows: ① In terms of seismicity, there are some anomalies such as seismic quiescence, high-frequency seismicity and seismic gap; ② In terms of geophysical observation, there are medium-term and short-term anomalies within 200 km of the epicenter, such as borehole strain, dominant azimuth of geoelectric field, apparent resistivity, and water level. The focal mechanism of the Ninglang MS 5.5 earthquake shows that the fault type of the earthquake is mainly normal fault by analyzing its earthquake sequence. The aftershock activity is abundant and the earthquake sequence has segmented characteristics. The magnitude difference between the main shock and the largest aftershock is 0.9, and the energy released by the main shock accounts for 93.53% in the whole sequence, therefore, the Ninglang earthquake sequence is primarily of mainshock-aftershock type. According to the comprehensive analysis, the medium-term and short-term anomalies of seismicity before the Ninglang MS 5.5 earthquake are prominent, and the geophysical observation anomalies are relatively abundant, which are distributed in northwest in Yunnan and surrounding area. This phenomenon has certain indicative significance for the occurrence of the Ninglang earthquake.
2023,44（6）: 1-12 收稿日期：2023-10-10
DOI：10.3969/j.issn.1003-3246.2023.06.001
基金项目：震情跟踪青年项目（项目编号：2023010309）
作者简介：冯晓博（1992—），男，硕士，主要从事地震地下流体方向的研究。E-mail：fengxb@seis.ac.cn
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