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Seamounts Explain Sunday Night’s Strong Earthquake in Jacó

The 6.9 magnitude earthquake that shook Costa Rica Sunday night is due to the friction exerted by the seamounts of the Coco plate when it submerges under the Caribbean plate, on which Costa Rica is located.

When sufficient energy is accumulated by the thrust of both plates, one against the other, the energy released translates into termors, explained Ivonne Arroyo, of the Red Sismológica Nacional, of the Universidad de Costa Rica (National Seismological Network of the University of Costa Rica).

From the USGS

The 6.9 quake occurred at 8:28 pm Sunday, southeast of Jaco, (15 km southeast of Esterillos, Lat: 9.4316 Long: -84.5302) in the Central Pacific ocean, at a depth of 19 kms, was felt throughout most of the country.

According to Arroyo, the Central Pacific region is one of the most (earthquake) active areas in the country.

Sunday’s quake is the fourth of significant magnitude to hit the area between Cobano and Osa. On March 25, 1990, a 7.0 quake hit the area of Cobano, the Quepos earthquake of August 199 was a 6.9 magnitude, the June 2002 quake in Osa was a 6.4.

Graphics from La Nacion

The geological conditions that affect Costa Rica are not measured in hundreds of years but in millions of years, according to Javier Pacheco, seismologist of the Observatorio Vulcanológico y Sismológico de Costa Rica (Ovsicori) – Volcanological and Seismological Observatory of Costa Rica – who says that the interaction of plates in the region has not varied in several million years.

“The seismic behavior of several centuries in the past and several centuries in the future, will be similar, it is not expected, nor is foreseen, any change. The speed of convergence between the two plates is the same: between seven and nine centimeters a year,” he assured.