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鲁甸MS 6.5级地震发生后,余震分布呈现两个优势方向，其发震断层是NE向的昭通—鲁甸断裂，还是NW向的次级断裂，引起了广泛的讨论。通过详细的野外调查发现，从龙头山镇南东方向的谢家营盘—光明村—王家坡一线N22°W—N55°W走向断续展布长约8 km地表破裂带，呈左行右阶排列，伴有30~35 cm左右的走滑分量，局部走滑分量达40~60 cm；明确了此次地震的发震构造为北西走向的包谷垴—小河断裂。通过探槽工程，揭露出发震构造的光明村—小垭口段4次古地震事件；8个炭屑样品的14C测年分析表明，事件E1可能发生在9 190~8 870 BC，E2为1 000 BC~900 AD，E3为910~1 240 AD，最新一次事件E4为2014年鲁甸MS 6.5级地震。该研究表明，云南地区6.5级强震可以产生地表破裂并可能在地质记录中留下遗迹。结合本次地表破裂特征，影像几何不连续以及探槽剖面揭露出古地震断面信息容易隐形等特征表明，包谷垴—小河断裂在历史活动中强度不大，属中强地震发震构造。
After the MS 6.6 Ludian earthquake, the distribution of aftershocks has two dominant directions, and whether the seismogenic fault is the NE-trending Zhaotong-Ludian fault or the NW-direction secondary fault has caused extensive discussion. Through detailed field investigation, we found that the surface rupture zone about 8 km in length from N22 ° W-N55 ° W on the first line of Xiejianying-Guangmingcun-Wangjiapo slope in the direction of south to the town of Longtoushan is left-right order With a strike-slip component of about 30-35 cm and a local strike-slip component of 40-60 cm. It is clear that the seismogenic structure of this earthquake is a northwesterly strike-valleys-stream fault. Through the trenching project, four paleoseismic events at the Guangmingcun-Xiaoyukou section of the seismogenic structure were uncovered. The 14C dating of 8 carbonaceous samples showed that event E1 could occur at 9190-8707 BC and E2 at 1 000 BC ~ 900 AD, E3 910 ~ 1 240 AD, the latest event E4 is the 2014 Luding MS 6.5 earthquake. The study shows that a magnitude 6.5 earthquake in Yunnan Province can cause surface rupture and may leave traces in geological records. Combined with the characteristics of surface rupture, the geometric discontinuity of image and the profile of the trenches reveal that the information of the ancient earthquakes is easy to be invisible, it shows that the strength of the Baoguandou-Xiaohe fault is not strong in historical activities and is a moderate-strong earthquake and seismogenic structure.