A 6.5 magnitude quake hit Saturday at 11:34 a.m. in the Pacific off the coast of Nicaragua. Either coincidentally or because of the strong quake, a lesser one took place a few seconds later a kilometer north of Sardinal de Carrillo in Guanacaste. That one had a magnitude of 4.9, said the Observatorio Vulcanológico y Sismológico de Costa Rica.
Then Saturday at 5:02 p.m. there was a 4.0 magnitude quake off the northern Pacific coast of Gauancaste.
All the quakes appear to have been the result of the subduction of the Cocos tectonic plate under the lighter Caribbean one.