October, November see few felt earthquakes

Some earthquake scientists are getting a little nervous because there were only seven felt earthquakes in the country in October and only three in November so far.

The November quakes were off Jacó and Quepos in the Pacific and near Pérez Zeledón. The magnitudes ranged from 3.6 to 4.4, enough to be felt as far away as Rivas, Nicaragua, in one case.

The largest October quake was Oct. 8. It was a 5.9 jolt northeast of Zarcero in the central mountains. Other quakes ranged from 3.3 to 4.9

The Red Sismologia Nacional is calling November one of the months with the fewest felt quakes. Meanwhile there are hundreds of small quakes that can only be detected with instruments.

Generally scientists like lots of light earthquakes because they believe this takes the pressure off the faults and prevents a larger quake.

The major production of quakes in Costa Rica is the interplay between the Cocos tectonic plate and the Caribe or Caribbean plate. The Cocos plate is being forced under the Caribbean plate. There is a clear line in the sea offshore in the Pacific where the junction between the two plates can be seen. However, the effects go far inland. The Zarcero quake was blamed on the release of tension between the two plates.

In fact, the nation’s central volcanic mountain range is a product of the relationship between the two plates similar to the rest of the Pacific ring of fire that runs from Asia through Alaska and down the Latin American coastline.

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