Probabilistic Hazard Assessment of Fault Displacements

Abstract eng:
A reliable estimate of potential fault displacements is needed in the engineering design of lifeline structures crossing potentially active faults, such as bridges, tunnels, dams, water pipes and gas lines. This paper outlines the methodology for the assessment of permanent ground displacement across a fault induced by an earthquake. Furthermore, application of the presented methodology to the South Iceland Seismic Zone is summarised, including presentation of hazard curves and a comparative study of the theoretical results and observed effects of some historic earthquakes. The presented model is probabilistic in nature and, to a certain degree, comparable to the models commonly applied in assessing peak ground acceleration (PGA) hazard. It includes both the uncertainties of the scaling laws of the ground motion effects and the frequency of earthquake occurrence. In addition, the model requires probability of surface rupture effects at the site as well as the conditional probability of a relative displacement over the fault, provided that the earthquake has ruptured the surface. The methodology is implemented using a Monte Carlo simulation technique. A relation between magnitude and displacement over the surface trace of the causative fault for the study sites is presented, as well as hazard curves of surface fault peak displacements, giving the fault displacements corresponding to a chosen mean return period. For example, at one of the study sites 1 m displacement was found to correspond to a mean return period equal to 3000 years, 58 cm for 1000 years and about 26 cm for 475 years.

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