Ground motion intensity measures for liquefaction hazard evaluation

The requirements of performance-based earthquake engineering place increasing importance on the optimal characterization of earthquake ground motions. With respect to liquefaction hazard evaluation, ground motions have historically been characterized by a combination of peak acceleration and earthquake magnitude, and more recently by Arias intensity. This paper introduces a new ground motion intensity measure, CAV(5), and shows that excess pore pressure generation in potentially liquefiable soils is considerably more closely related to CAV(5) than to other intensity measures, including peak acceleration and Arias intensity. CAV(5) is shown to be an efficient, sufficient, and predictable intensity measure for rock motions used as input to liquefaction hazard evaluations. An attenuation relationship for CAV(5) is presented and used in an example that illustrates the benefits of scaling bedrock motions to a particular value of CAV(5), rather than to the historical intensity measures, for performance-based evaluation of liquefaction hazards.