云南地区中小地震震源机制解及分区特征分析

Analysis of focal mechanism and regional characteristics of medium and small earthquakes in Yunnan region

利用云南地区2008年至2022年4月M_(W)≥3.0共1096个地震震源机制解,进行统计和区域构造应力场特征分析.结果表明:①云南地区震源机制解以走滑断层型为主,走滑断层型地震为702个,占比为64%;其次是正断层型地震为125个,占比为11.4%,说明云南地区断裂以走滑断层型和正断层型为主;②云南地区以走滑断层型地震占比最多,滇西北地区的正断层型地震占比显著高于其他区域,小滇西地区几乎没有逆冲型大断层;③云南地区断层受到的应力以水平向剪切应力为主,主压应力轴P轴的方位角的优势分布方向以NNE和SSW向为主,断层面多为高倾角,滇西北地区正断层型地震显著多于其他地区,说明滇西北地区是云南地区应力转换带.

Based on the focal mechanism solutions of 1096 earthquakes with M_(W)≥3.0 from 2008 to April 2022 in Yunnan region,the characteristics of regional tectonic stress field were analyzed statistically.The results showed that:①There were 702 strike-slip earthquakes in Yunnan,accounting for 64%of the total.The second was 125 normal fault type earthquakes,accounting for 11.4%,indicating that the faults in Yunnan were mainly strike-slip and normal fault type.②The proportion of strike-slip earthquakes in Yunnan was the largest,and the proportion of normal fault earthquakes in Northwest Yunnan was significantly higher than that in other regions.There were almost no large thrust faults in small western Yunnan.③The stress of faults in Yunnan was mainly horizontal NS shear stress,and the fault plane has high dip angle.The normal fault earthquakes in Northwest Yunnan were significantly more than those in other areas,indicating that Northwest Yunnan was a stress transition zone in Yunnan.