The 14th World Conference on Earthquake Engineering

The objective of the study presented herein is to access the influence of rupture directivity on the inducement of liquefaction in loose, saturated sand. Rupture directivity is a near fault phenomenon that results in a pronounced double-sided velocity pulse in the strike normal component(s) of motion. Using the Palmgren-Miner fatigue theory, implemented for low cycle fatigue conditions, the number of equivalent cycles were computed for twenty seven sets of strike normal and strike parallel components of motions, where the former components had the pronounced velocity pulses and the latter did not. Using these results and other results from site response analyses, the cyclic stress ratios adjusted to M7.5 were computed for both components of motions in a soil profile at a depth corresponding to ~1 atm of effective vertical stress. Two clear trends where identified. First, the strike normal components tended to induce larger cyclic stresses in the soil than the strike parallel components. However, the strike normal components of motions had fewer numbers of equivalent cycles as compared to the strike parallel components. Although these trends are somewhat compensating in their influence on the inducement of liquefaction, the net result was that the motions containing the rupture directivity pulses had a slightly larger potential to induce liquefaction than motions without the pulses.