“…Sequential data assimilation techniques, such as the particle filter, PF (Gordon et al, 1993;Kitagawa, 1996;Higuchi, 2005), are prospective approaches for this type of inverse problem, because the time evolution of state variables, i.e., displacement and pore pressure for geotechnics, under controlled input, like external loading, is incorporated into the system equation in a rational manner without any limitations. The PF can easily deal with nonlinear state equations and is robust when employing the Monte Carlo method in conjunction with a numerical simulation, e.g., the FEM for soil-water coupled problems with an elasto-plastic model (Shuku et al, 2012;Murakami et al, 2013).…”