The Observatorio Vulcanológico y Sismológico de Costa Rica said that the larger quake was about 510 kilometers (316 miles) northwest of La Cruz, Guanacaste.
The Gulf of Nicoya quake was in about the same area as one last Nov. 2 and also one March 25, 1990, that was estimated at 7.0 magnitude and caused substantial damage on the peninsula.
The Laboratorio de Ingeniería Sísmica estimated the epicenter at the mouth of the gulf to be about 27.5 kilometers (16 miles) east of Cabo Blanco at the peninsula’s tip and 25.7 kilometers (17 miles) west southwest of Jacó in the central Pacific coast. The quake took place at 4:08 p.m., said the Laboratorio, which said the magnitude was 3.0. The Observatorio Vulcanológico y Sismológico estimated the magnitude at 2.7.
There were two other felt quakes Tuesday. The first was at 43 minutes after midnight near San Carlos de Tarrazú. The magnitude was estimated at 2.5 by the Observatorio. A bit more than an hour later, at 1:46 a.m., a quake took place northeast of Golfito in the southern mountains. The Observatorio said the magnitude was 2.5.
Earthquake experts have been predicting a major event somewhere in the Gulf of Nicoya or further to the north. There was a flurry of quakes at the mouth of the gulf Nov. 2 with the largest being estimated at 5.4. Earthquake scientists do not see these events as a sign of bigger quakes to come, but many residents think that these smaller quakes take the pressure off the internal stresses of the earth’s crust, and they welcome them.
Costa Rica is one of the most earthquake-prone and volcanically active countries in the world, according to the University of California at Santa Cruz, which has studied the area extensively. Just off the west coast is the Middle America Trench, where a section of the sea floor called the Cocos Plate dives beneath Central America, generating powerful earthquakes and feeding a string of active volcanoes, said researchers. This type of boundary between two converging plates of the earth’s crust is called a subduction zone ― and such zones are notorious for generating the most powerful and destructive earthquakes.
Scientists have been trying to prepare Nicoya residents for what they believe is an inevitable major earthquake. In fact, the Red Sismológica Nacional at the Universidad de Costa Rica held general meetings for Nicoya residents a year ago to alert them and suggest ways to prepare.