Scientists counted more than 3,000 quakes in 2010

Red dots mark the estimated epicenters of earthquakes registered by the Red Sismológica Nacional in 2010.

More than 3,000 earthquakes took place in and around Costa Rica in 2010. Most were too small to be felt, and the nation avoided any serious quake damage.

That is the report from the Red Sismológica Nacional, which is based at the Universidad de Costa Rica. It is one of the two major academic organizations that study earthquakes and volcanoes.

The Red reported it registered 111 quakes in 2010 that were felt by the population. Just 58 of these were the result of subduction of the Coco tectonic plate under the Caribe plate. There were 14 quakes with a magnitude of from 5.0 to 5.9. The two largest quakes were at Zarcero and 25 kilometers off the coast of Quepos. There was no serious damage from either.

The bulk of the felt quakes clustered around three points: the tip of the Nicoya peninsula, south of Golfito at the Panamá border and east of San José and Cartago in the vicinity of Volcán Irazú and Volcán Turrialba.

January was the big month for quakes, and there were more than 30 felt quakes reported. Between Jan. 23 and 25, there were 60 quakes in the extreme southwest of the country and in adjacent Panamá. Most were not strong enough to be felt by humans. That area in the vicinity of the Burica peninsula is where the Coco and Nazca tectonic plates interact with the Panamá Block. The area is intensely active.

Some earthquakes are related to volcanic activity, and Volcán Tenorio showed increased activity with a 3.4 quake July 6 that was felt in Bijagua de Upala and the vicinity in northern Costa Rica. The quake spawned at least 24 mini-quakes.

Volcán Arenal was more notable for its eruptions and pyroclastic flows than for quakes. Volcán Poás also had a series of strong eruptions beneath the lake in its crater in May.

The Irazú and Turrialba volcanoes hosted dozens of smaller quakes, but acid rain and gas emissions from Turrialba were studied more.

Turrialba represents a threat to farms, pastures and homes within a five-kilometer radius of the main crater, said the Red Nacional. It estimated that a major eruption would affect up to 1.5 million persons.

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