Clarifying the differences between traditional liquefaction hazard maps and probabilistic liquefaction reference parameter maps

Abstract

Traditional liquefaction hazard maps are useful tools for preliminary engineering site assessment and policy development. However, these maps should not be used for site-specific liquefaction hazard assessment. Simplified probabilistic liquefaction analysis procedures can be used instead to perform site-specific liquefaction hazard assessment, but these procedures rely on probabilistic reference parameter maps that are not yet familiar to most engineering and geological practitioners. As a result, some professionals are questioning the differences between traditional liquefaction hazard maps and the new probabilistic reference parameter maps. This paper clarifies the differences between these two types of maps, and shows how each of these maps complements the other. New probabilistic reference parameter maps for liquefaction triggering and lateral spread displacement are developed and presented for San Diego, California, and simplified probabilistic equations necessary to use the reference parameter maps are summarized. An example map-based liquefaction triggering and lateral spread displacement analysis is performed for a representative site near San Diego Bay. Results of the analysis demonstrate that the probabilistic assessment confirms and augments the information conveyed by the traditional liquefaction hazard map.