You probably felt the 6.1-magnitude earthquake on Saturday, October 12, around midday. That was just one of several times the ground likely shook under your feet in recent weeks, as the National Seismological Network (RSN) recorded 96 earthquakes with magnitudes above 3.0 in an area near the Guanacaste coast between Sunday, October 6, and Tuesday, October 15.
This has sparked dozens of news reports and hundreds of comments on social media, filled with theories about what is happening. At The Voice, we turned to RSN seismologist Lepolt Linkimer to find out how accurate some of these social media comments are and to provide you with clear explanations. All these answers were prepared based on Linkimer’s explanations:
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These tremors are a sign that an earthquake is coming. FALSE
We would all like to know where and when the next earthquake in Costa Rica will occur, but unfortunately, we still can’t predict them. What is true, however, is that we are observing an increase in seismic activity, which peaked on Sunday, October 13, but decreased by October 14 and 15. Although the tremors are subsiding, we cannot confirm whether an earthquake will occur or not, as this is a tectonic plate boundary zone where earthquakes are common.
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Small tremors release energy that prevents an earthquake. FALSE
This is, unfortunately, a myth. Small tremors do not “release energy.” For that to happen, thousands of them would be required. For example, to release the same amount of energy as a 6.2-magnitude earthquake, like the one on Saturday, October 12, it would take 63,095 tremors of magnitude 3.
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This seismic activity is leftover energy from the 2012 earthquake. FALSE
These events are occurring in a different area from where the 2012 Sámara earthquake took place. The current tremors are being recorded 100 kilometers northwest of the epicenter of the Sámara earthquake, in a separate subduction zone (where one tectonic plate sinks beneath another).
In the past, however, a major 7.0-magnitude earthquake did occur in 1916, closer to the epicenters of this week’s seismic activity.
Historical Fact:
The 7.0-magnitude earthquake on February 27, 1916, seems to have occurred about 25 kilometers off the coast, near Playas del Coco. Since it was an old earthquake, it is more challenging to study. At that time, the country didn’t have instruments like those we have today to accurately determine its location. The way we study historical earthquakes is through the effects they caused. It is most likely that its epicenter was in the Papagayo Gulf area.
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The deeper the origin of these tremors, the lower the impact. TRUE, but…
Seismic waves lose energy as they travel through the Earth, and this principle applies both to the depth of the rupture and the distance from the epicenter.
However, depth is just one factor in determining whether an earthquake causes damage. Other key factors include the magnitude of the tremor and the number of people exposed. If an earthquake occurs relatively close to a city, it is very likely to cause significant damage.
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This area is more active than in previous decades or recorded periods. FALSE.
From 2015 to the present, the seismicity rate has remained fairly stable. What we do have, however, is more data thanks to better instruments and equipment that can detect even the smallest movements. This doesn’t mean that more tremors are occurring, only that we are now able to record them more accurately.
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Tremors in the ocean can trigger other tremors on land. TRUE, but…
Sometimes, one earthquake can trigger another. In Costa Rica, we have no way of predicting this, but it has happened in the past. For example, the 6.0-magnitude Bagaces earthquake in 1941 occurred just four hours after the 7.3-magnitude Golfito earthquake that same year.
We cannot currently say if the 6.2-magnitude earthquake on October 12 will trigger another, but we cannot rule it out, as it has been observed in the country’s history.
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Earthquakes in the ocean have caused tsunamis in Guanacaste. TRUE.
Guanacaste has experienced tsunamis. One occurred in 1992, triggered by an earthquake off the Pacific coast of Nicaragua. It caused severe flooding in Playas del Coco and other coastal areas, but Costa Rica reported no casualties. Unfortunately, in Nicaragua, more than 170 people lost their lives.
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