Current procedures for evaluating potential earthquake-induced liquefaction and lateral spreading appear to have a tendency to over-predict liquefaction effects in interbedded sand, silt, and clay deposits. Possible reasons for overprediction of liquefaction effects are discussed, and investigations regarding some factors pertinent to use of the cone penetrometer are described. An axisymmetric direct cone penetration model is presented for use with the MIT-S1 constitutive model to explore cone penetration processes in a range of soil types; current efforts are focused on validating this new direct cone penetration model, beginning with simulations of cone penetration in soft clay. The relationship between cyclic strength and cone penetration resistance in non-plastic and low-plasticity fine-grained soils is examined by relating cyclic strengths from laboratory tests to cone penetration resistances from simulations. The performance of a site underlain by interbedded soils along the Çark canal during the 1999 M=7.5 Kocaeli earthquake is analysed using one-dimensional lateral displacement index procedures and two-dimensional nonlinear deformation analyses with spatially correlated stochastic models to illustrate how several factors can contribute to an over-prediction of liquefaction effects. Future research needs and directions for improving the ability to evaluate liquefaction effects in interbedded sand, silt, and clay deposits are discussed.