The 1933 Diexi Ms 7.5 earthquake occurred along the Upstream Minjiang river, at the eastern margin of the Xizang(Tibetan) Plateau. Its seismogenic structure remains enigmatic. Two views were proposed by previous studies. One attributed it to sinistral strike slip on the NW—SE striking Songpinggou fault; another to sinistral strike slip on the N—S striking Minjiang fault. But the survey results of coseismic surface ruptures, seismotectonics and iso seismal maps did not support this strike slip faulting model of the earthquake. Based on field investigation of morpho structures of the dammed lake in the Diexi area and faults affecting the latest Pleistocene lacustrine deposits, and by taking into account historical earthquakes and paleoearthquake studies in this zone, we propose in this paper an alternative view of seismogenic structure, analogous to that for the 2013, Lushan Ms 7.0 earthquake that ruptured the southern segment of the Longmenshan fault zone. This model, namely the buried ramp type thrusting, considers a W dipping ramp at depths of 10~15 km beneath the Minjiang stream, which thrust eastward and produced repeated earthquakes in this deeply incised valley. By consequence, no active fault trace responsible for historic earthquakes has been seen to run through the river valley, only some normal faults were observed in the lacustrine deposits of the Diexi dammed lake, which were dated to be deposited in a time span of 30 to 10 ka BP. Kinematics of normal faults indicates either NW—SE extension or NW—SE extension, suggesting that they were formed in association with landslides of the earthquakes. However, this view is to be tested in the future by geophysical and geodetic investigations.