Premise: The 1974 Zhaotong earthquake occurred at 19:25 UTC on 10 May. It had a magnitude that was measured at 7.0 on the moment magnitude scale and 7.1 on the surface wave magnitude scale. It had a maximum perceived intensity of IX ("Violent") on the Mercalli intensity scale. The epicenter was located in Zhaotong prefecture in Yunnan province and it caused between 1,641 and 20,000 deaths.
Hypothesis: the 1974 zhaotong quake occured during the winter