Abstract: The coda-wave attenuation quality factor Q_c in Yunnan region is estimated using the single-scattering attenuation model of Sato based on 5668 local seismic events recorded by 22 regional digital seismic stations from the later half of 1999 to 2003. The events used in this paper are situated within epicentral distances of 50 km. According to the variation of Q₀ and η, we classified the quality factor Q_c into two types. The classified results show that there are regional distribution characteristics in medium structure in Yunnan region, and the characteristics could be elementarily interpreted by geological structures, seismic activity and heat flow. Generally speaking, the quality factor Q_c in Dianzhong center Yunnan region Block and its boundary area is notably less than that in other regions, where the tectonic activity isn't intense. According to seismic activity, there are large earthquakes in the areas with lower Q_c, and there are few or only some little earthquakes in the areas with higher Q_c. Besides, there is negative relation between quality factor Q_c and heat flow in Yunnan region, namely higher heat flow corresponds to lower Q_c and lower heat flow corresponds to higher Q_c.

Key words: Yunnan region, Coda Q_c, Sato's single-scattering attenuation model, Regional distribution