Observations on Earthquake Acceleration and Pore Water Pressure in a Hilly Region

Abstract

Earthquake accelerations and pore water pressures were measured on a hill slope to constrain slope stability reduction caused by earthquakes. Acceleration responses were observed at various locations on and under the ground surface on a ridge slope and in neighboring valley fill units. Pore water pressure in the valley fill was also measured during earthquakes. The amplification of the acceleration response that was transmitted from underground to the ground surface was compared between sites. The acceleration responses became greater when an earthquake was transmitted from underground to the ground surface. Large earthquake accelerations on the ridge of the hill were amplified primarily in a direction perpendicular to the ridge crest. They were also amplified at specific frequencies by the topological effect. In contrast, earthquake accelerations in valley fill sediments were equally amplified in all directions and over a wide frequency band. Increases in the dynamic pore water pressure tended to be synchronized with increases in vertical acceleration.