This study of the earthquake response of a small valley in Kirovakan during the 1988 Armenia Earthquake demonstrates how 2D ground motion simulations provide a suitable explanation of the observed damage in situations where 1D soil amplification analyses have proved to be unsatisfactory. The 2D simulations predict maximum ground and structural response in the frequency range of 2.5 to 4.5 Hz, which corresponds exactly to the natural frequencies of the four- to five-story structures which experienced the greatest damage. It appears that this damage occurred as a consequence of double resonance between the excitation, the valley, and the building structures. The amplitude of the double resonance was greatly enhanced by the finite lateral extent of the valley.
A novel way of visualizing structural response as a simultaneous function of the natural frequency of the structure and its location within the valley was introduced in this study. This allows one to identify the types of structures that are prone to suffer extensive damage and the locations within the valley where this damage is most likely to occur. In certain regions the soil and structural responses are seen to vary rapidly over short distances. This behavior, which has been observed during actual earthquakes, has practical implications for design.
In this study only one particular incident wave was considered. While thus restricted, results of this study suggest that simulations using realistic valley models could be used to great advantage in seismic zonation and seismic hazard analyses. Different earthquake scenarios consistent with the particular tectonic settings should, of course, be considered, and the simulation results integrated with those from observations. One might use a probabilistic approach to include effects from uncertainties in the source and model parameters.