Probabilistically-based estimates of seismic slope displacements

Estimates of seismically induced permanent displacements can be computed directly through an attenuation relationship, or indirectly using a two-step approach that first estimates the value of an intermediate intensity measure, and subsequently computes the displacements through a correlation with this intensity measure. This paper proposes a direct attenuation relationship for seismic displacements and correlation models for displacement against three selected Intensity Measures (i.e. peak ground acceleration, spectral acceleration, and arias intensity). The proposed relationships are based on simulated displacements from a coupled stick-slip linear generalized single degree of freedom model. Comparisons of the computed displacement probability density functions for different earthquake scenarios are made. It is found that no approach is better in terms of reducing the overall uncertainty, but the indirect method with an intensity measure that is well correlated to seismic displacements allows for fewer advanced analyses to be performed. A case history is presented to illustrate the use of all approaches.