The April 22, 1991 Limón (Costa Rica) earthquake

Abstract

The 1992 main Limón earthquake had Ms 7.6, strong-motion duration (at San Isidro) 26.6s and maximum MM intensity XI. With epicenter near the Caribbean coast, the shapes of its isoseismals differ markedly from the code-specified isoacceleration curves for various return periods, as the latter curves assume that all seismic sources are close to the Pacific coast. On the other hand, code design spectra are overly conservative for structures in the long period range, especially on soft soil. These matters demand a code revision. Although the death toll was moderate, there was considerable material damage especially in the province of Limón, including widespread liquefaction and ground failure, which damaged roads and railways. Main causes for damage to buildings were, as is often the case, insufficient transverse reinforcement, poor detailing, short columns prone to brittle failure in shear, and soft first story. Storage-tank and bridge failures are also analyzed. The danger of a macroseism within densely populated areas is brought out.