The April 22, 1991 earthquake in Costa Rica triggered widespread ground failures: soil liquefaction and spreading; foundation failure of bridge abutments due to soil liquefaction; and landslides. Liquefaction-induced ground failures are poorly understood, and as a consequence, only crude criteria have been developed for predicting their occurrence, and the destructive capability of these events. This recent earthquake in Costa Rica provides an unexpected opportunity to make detailed field observations and measurements, resulting in a well-documented set of case histories. Such case histories aid in understanding the ground failure process; they also provide benchmark events for verification of analytical and empirical predictive models. The principal objective of this research project is to make detailed topographic and ground displacement measurements at several liquefaction-induced ground-failure sites in Costa Rica. The ground surface effects to be measured are features that will soon disappear.
