Physical mechanisms that contribute to the generation of abnormally high accelerations >1g in earthquakes at soft soil sites, where nonlinear behavior reducing accelerations is considered typical, are discussed. The models constructed of soil behavior (vertical distributions of stress and strain in soil layers) have shown that the nonlinearity of the soil response at the stations where the recorded accelerations exceeded 1g was usually insignificant, because of the rather low motion imposed on the soil layers: PGA ~ 120–270 cm/s2. The generation of abnormally high accelerations at sites with soft subsurface soils was obviously related to (1) the response of subsurface soils that effectively amplified strong motions due to the character of the stress–strain relations; (2) resonant phenomena in soft subsurface layers; and (3) the effects of directivity (during strong earthquakes with extended sources), i.e., constructive interference of seismic waves in the directions of crack propagation along the fault planes.

中文翻译：

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地震期间软土上产生>1g异常高加速度的机制

讨论了导致在软土场地地震中产生异常高加速度 >1g 的物理机制，其中非线性行为减少加速度被认为是典型的。由土壤行为（土壤层中应力和应变的垂直分布）构建的模型表明，在记录的加速度超过 1g 的站点，土壤响应的非线性通常是微不足道的，因为施加在土壤层上的运动相当低：PGA ~ 120–270 cm/s2。地下软土场地异常高加速度的产生显然与（1）地下土壤的响应由于应力-应变关系的特征而有效地放大了强烈运动；(2) 软地下层共振现象；