Earthquake Microzoning from Soil Properties

Abstract

The extent of damage caused by an earthquake in Wellington, New Zealand, in 1968 to buildings erected on a variety of regoliths and foundation materials is correlated with the thickness of the regolith, the depth to the water table and semi-quantitative parameters derived from soil profile descriptions, particularly related to soil type and soil structure. From linear regression correlations, the expected damage for a comparable earthquake elsewhere can be determined. The model was tested for soil data for the Edgecumbe area, hit by a damaging earthquake in 1987. The predictions were sufficiently in accord with observations to suggest that soil properties that reflect the geotechnical properties of the upper parts of the regolith, particularly those that measure the shear strength, shear wave velocity and viscous damping of that material, may be useful for earthquake microzoning purposes in areas where there is a considerable thickness of unconsolidated materials above bedrock.