The Guatemala earthquake and Caribbean Plate tectonics

Abstract

The main fault along which the destructive Guatemala earthquake occurred was the Motagua fault. Ground breakage was observed in a continuous, well-defined line for 230 km. At its closest point, the fault is 25 km north of Guatemala City. Surface displacement across the fault was dominantly horizontal and sinistral (see back cover). The strike-slip component averaged 1.08m and was as high as 3.40m. Unlike many other earhtquake-related strike-slip displacements in the world (such as the San Andreas system in California), subsidiary faults, splays, and an echelon offsets are relatively rare along the Motagua fault. Most of the fault trace is marked by linear stream valleys, minor scarps, shutter ridges (a fault-displaced ridge which "shuts in" the adjacent canyon), and sag ponds (fault-formed depressions which fill with water).