通过对 1 995年永登地震形成的黄土震陷场地现场考察及震区震陷形成的地震动和黄土厚度条件 ,用震区震陷试验曲线计算了震区试验震陷量 .并通过震区震陷黄土和未震陷黄土微结构对比分析 ,探讨了黄土震陷形成的机理 .结果表明 ,震区试验计算的震陷量略小于实际地震震陷量 ;黄土震陷产生的机理为地震力剪切作用下孔隙结构破坏 ,在重力和压力作用下振动质密所致 . Based on the site investigation of loess seismic subsidence caused by the Yeongdeung earthquake in 1995 and the conditions of the seismic motion and loess thickness caused by the earthquake subsidence, the experimental study was conducted to calculate the amount of subsidence in the earthquake zone test. The comparison of the microstructure of the loess and unshaped loess shows that the formation of the loess subsidence mechanism is discussed.The results show that the calculated amount of the subsidence is slightly less than the actual amount of the earthquake subsidence, and the mechanism of the loess subsidence is the seismic force Pore ​​structure under shear damage, under the action of gravity and pressure due to vibration and density.