Abstract: Some syndepositional soil-layers disturbed by earthquakes were discovered in thick-bedded alluviums of Eocene Zhubidian formation in Anqiu area of Tancheng-Lujiang seismic zone.Through the field observation and comparative seism-geologic studies,many seism-genesis soil-layer structures such as vibration-liquefied sand vein,vibration-liquefied sand dyke,sandy cobble dyke by fissure filling,seismic fall mass,seismic intra-layer fault and seism-settlement structures etc.were recognized.The seismic structures were records of earthquake events of magnitudes ranging from 5 to 8.5.According to the analysis of dynamic characteristics of these seismic soil-layer structures,it was proposed that failure functions of foundation caused by strong earthquakes included liquefaction,seismic fissure filling,vibration falling,fracturing and seismic settlement of soil.