During the field work, softsediment deformation structures in lower Jurassic Kangsu Formation lacustrine deposits were recognized in the northern part of Wuqia, western Xinjiang Uygur Autonomous Region. Deformation structures are represented by load cast, ballandpillow structure and convolute lamination. The mechanism of deformation is related to liquefaction and or fluidization triggered by a paleoseismic event by comparing with the simulation test. According to the correlation between the earthquake magnitude and the maximum epicentral distance of liquefaction, the magnitude producing the lower Jurassic softsediment deformation can be predicted as 6