The earthquake sequence of May 1951 at Jucuapa, El Salvador

Three earthquakes that happened over two days in May 1951 caused extensive damage to villages in a small area of eastern El Salvador (Central America) . Contemporary hypocentral solutions indicated focal depths, confirmed by r e-calculations using available seismic data, of the order of 90 km, suggest ing events associated with the subducted Cocos plate. Macroseismic observat ions strongly indicate that the earthquakes were of very shallow focus and this is supported by wave-form modeling and the appearance of seismograms r ecorded in Guatemala. A re-evaluation of the location and source characteri stics for these events is presented, together with a fault plane solution a nd additional macroseismic evidence. The implications for seismic hazard an d risk assessment in Central America, where shallow earthquakes of moderate magnitude, frequently occurring in clusters, pose the greatest threat to s ettlements which, like the area affected by these events, are concentrated along the axis of Quaternary volcanoes.