ABSTRACT
Accelerations and pore pressures recorded as liquefaction and ground deformation developed at the Wildlife site during the 1987 Superstition Hills earthquake define the following relationships: (1) Cyclic shear deformation is the primary mechanism leading to generation of excess pore water pressures. (2) Once pore pressure ratios exceeded about 20 percent, ground oscillation became the dominant mode of ground deformation. (3) The amplitude of ground oscillation increased after strong ground shaking ceased due to excitation by low-amplitude, long-period seismic waves. (4) Increased oscillation amplitudes increased cyclic shear deformations and continued the generation of pore water pressure after strong shaking had ceased. (5) Shear-strain induced dilatency at the northern end of the oscillation excursions transiently decreased pore pressures, strengthened soils, arrested movements, and generated negative pore-pressure and acceleration spikes in instrumental records.
