Prediction of Liquefied Strata from the 1987 Edgecumbe Earthquake

On March 2 1987, an earthquake of magnitude (ML) 6.3 occurred near the town of Edgecumbe, in the North Island of New Zealand. Extensive ground damage in the form of liquefaction and surface faults resulted from the shock, especially in the recent sediments of the Rangitaiki Plains surrounding Edgecumbe. This paper focuses on a major lateral spreading site, at the Landings Road Bridge, which lies on the eastern side of the Rangitaiki Plains. The liquefaction beside the bridge produced both sand boils and lateral spreading of the overburden towards the river. Data from the probes and the use of empirical and semi-empirical models enabled the prediction of which strata liquefied during the earthquake. A three-dimensional model of the lateral spreading in this area was established, and a verification of lateral spreading models was accomplished.