Two Dimensional Analysis Of Ground Motion Characteristics On Irregularly Layered Media

Abstract

Two-dimensional response analyses of the ground are conducted to study the effects of geometric irregularities of subsurface layers on the seismic ground motion characteristics. The relation between the maximum acceleration, displacement and acceleration response spectrum on the ground surface and their distribution and geometric irregularities of surface layers is discussed and twodimensional responses are compared with one-dimensional ones of the horizontally stratified layers. INTRODUCTION The seismic ground motion characteristics in the surface strata were mainly studied by one-dimensional approaches, assuming vertical propagation of shear waves. However, it has been well recognized that the ground motions are strongly affected by twoor three-dimensional ground irregularities based on the recent accumulation of strong motion records and development of analytical procedures. For example, it was reported that the ground motion in Mexico City was mucn amplified by the soft basin sediment In the 1985 Mexico Earthquake [1] . From this point of view, two-dimensional earthquake response analyses for subsurface ground models are conducted to study the ground motion characteristics Induced by irregular soil profiles A computer program FLUSH [2] Is employed in numerical calculations for two-dimensional ground models. Two kinds of subsurface ground models are considered; Inclined Base Model and Basin Model, and the dimensions of geometric irregularities: Inclined base gradient and spread of surface layer are parametrically changed The maximum acceleration, displacement and acceleration response Transactions on the Built Environment vol 3, © 1993 WIT Press, www.witpress.com, ISSN 1743-3509