NONLINEAR SOIL RESPONSE IN-GROUND MOTIONS

From both theoretical and empirical studies, we know that a soft soil layer will amplify seismic waves of certain frequencies and cause dama ge to structures, depending on the physical properties and the thickne ss of the layer. Most developed cities are situated on a plane or a ba sin with soft geological strata. Thus, understanding the characteristi cs of soft soil response to seismic loading is important. Seismologist s and engineers are interested in questions of linear versus non-linea r soil response and isotropy versus anisotropy as a soil property, The records of the downhole accelerographs of an array in Lotung provide an opportunity to study these problems. The results show that the soil response in Lotung does not have an anisotropy effect, and significan t non-linear soil response occurred during the strong ground motions i n which peak ground acceleration values at ground surface are larger t han 150 gal.