Abstract: Features of seismic sequence can directly reflect the differences among tectonic stress field, seismotectonic and seismogenic environment. For example, mainshock-aftershock-type earthquakes mostly occur in a relatively uniform medium environment. However, foreshock-mainshock-aftershock-type earthquakes and swarms mainly occur in complex structure. On 17 June, 2019, the M6.0 an earthquake occurred in Changning County, Yibin City, Sichuan Province. Its aftershock totally distributed along a NW direction belt, bit in the northwest part of the belt, the aftershock distribution showed the cluster features. There is an obvious difference between the southeast part and northwestern part for aftershock activity. The southeast part can be considered as a mainshock-aftershock type with a fast decay. The northwestern part shows a feature of swarm, which decay is slowly and many aftershocks with M5 or more in the early stage. The M6.0 earthquake occurred in the Changning-Shuanghe anticline which is complicated and composed of several secondary fold structures and associated faults. The segmentation characteristics of the Changning M6.0 earthquake indicate that it is hardly to be produced by a single fault but a cascade fractures. Moreover, the aftershock focal depths in the northwestern part are more deeply, this means that the seismic activity in this area has been controlled by the Huaying Shan fault zone. Oppositely, the possible influence of the 2019 Changning M6.0 earthquake on Huaying Shan fault zone should be emphasized in the future.

Key words: The 2019 Changning M6.0 earthquake, Seismic sequence, Tectonic environment