San José and much of the Greater Metropolitan Area (GAM) have the “breeding ground” needed to experience an earthquake of deep origin, such as the one that shook Mexico City and its surroundings last month.
The earthquake in Mexico had a magnitude of 7.1 degrees and a depth of 60 kilometers. In the case of the Costa Rican capital, the National Seismological Network (RSN) explained that the plate of the Coco is right below -80 kilometers deep. This is a potential source of tectonic movements.
Although Costa Rica has never faced earthquakes of such depth, the possibility is there.
If there is such a movement -with a magnitude of 7 degrees- considerable damage could occur.
Of course, the type of soil in the Mexican capital contributed to the effects of the earthquake of September 19th.
It is true that the city of San José is threatened by deep earthquakes. If they reach high magnitudes, they could also generate considerable intensities that could cause damages,”
said Lepolt Linkimer, geologist of the RSN.
The geological conditions where the Mexican capital is settled, especially the type of soil, magnify the intensities of events.
“Mexico City is located in an area that favors the amplification of seismic waves and an increase in the intensity of the soils in which it is located. If an earthquake occurs distant to San José (or deep) it is very likely that the intensities are not as high as those that occur in Mexico, because it is not in so soft soil. They have that particular geology situation,” added Linkimer.
Usually, Costa Ricans are concerned about surface earthquakes -whose epicenter is located a few kilometers deep- due to the repercussions and damages that have generated in the past. However, in other countries such as Chile or Perú, deep earthquakes were devastating.
If several events are concatenated with the deep earthquake, they can be potentially destructive. If we imagine an earthquake like this just below San José, we would be 80 kilometers from the source of the seismic waves. For an event greater than 7 degrees, the waves would not have weakened enough and would generate high intensities,”
added the researcher.
Data compiled by the scientific authorities show that in November 1948 there would have been a deep earthquake of 7 degrees that caused damage in the central part of Costa Rica. As there were no adequate instruments at the time, they have no relevant scientific data.
In addition, in March 1992 a 6.2-magnitude earthquake occurred at a depth of 80 kilometers with an epicenter in Naranjo de Alajuela.
The depth is connected to the area of perception of the earthquake. A superficial earthquake, such as that of Cinchona (in 2009, magnitude 6.1), feels intensely in a reduced area. However, the waves dim quickly and -for example- in Guanacaste it was not perceived. In a deep earthquake of the same magnitude, you will feel less intensity but the area of perception will be very large,”
said the seismologist.
It should be noted that the country is part of the so-called Fire Belt that links Chile to New Zealand. There are 24 different countries, including Argentina, Colombia, Mexico, the United States, Russia, Japan, Taiwan and Samoa. The latter has the most important seismic activity on the planet.