A moderate earthquake in western Costa Rica flowed through the Central Valley in two quick waves early today. The strongest quake at 1:08 a.m. was preceded by a lesser one about 19 minutes earlier and followed by one 25 minutes later. The location was south of the community of Orotina in Alajuela province.
There was a 3.0 quake at 49 minutes after midnight that was estimated to have an epicenter two kilometers northwest of San Francisco de Turrubares. At 1:08, a quake, estimated at 5.2 by the Observatorio Vulcanológico y Sismológico, took place in nearly the same spot, a kilometer southwest of the same community. Then at 1:33 a.m. there was a quake estimated at 3.2 about two kilometers south of Hacienda Vieja de Orotina. All the estimated epicenters are close.
The Red Sismológica Nacional estimated the 1:08 a.m. quake at 4.9, and the Laboratorio de Ingeniería Sísmica said the magnitude was 5.0.
The Red Sismológica Nacional attributed the quakes to the subduction of the Coco tectonic plate under that of the lighter Caribbean. This is a usual cause of quakes in western Costa Rica. The quake was felt in a large part of Costa Rica, said the Red.
The quake was felt strongest in eastern San José and in San Pedro, according to measurement by the Laboratorio. The quake came in two waves several seconds apart. The strength was enough to awaken some who were asleep.