NONLINEAR SITE RESPONSE AND ITS EVALUATION AND PREDICTION

Nonlinear behavior of a soft surface ground during strong earthquakes are reviewed and discussed. Firstly, dynamic deformation characteristics of soil are reviewed briefly. Then method of nonlinear analysis and its accuracy is discussed. Finally, vertical arrays where strong ground motions were recorded are introduced. Researches using these strong motion data are also reviewed to identify the occurrence of the nonlinear behavior and to explain the ground shaking. Through the review, nonlinear behavior is confirmed to occur in these sites and importance to take nonlinear behavior into account in predicting the site response is recognized. Equivalent linear analysis is shown to be a good approximation when maximum strain is less than about 0.5%, but not applicable at a liquefied site. Effective stress analysis is shown to be better than nonlinear total stress analysis, and nonlinear analysis is better than equivalent linear analysis.