ORn total of 111 earthquakes –four of them during the last three days– have shaken the waters between Tenerife and Gran Canaria, in the place where the Enmedio volcano is located, since the beginning of the year 2023. This figure already represents more than a quarter of the earthquakes that occurred in this same area during the previous year, although the researchers still do not consider that it is a symptom of an increase in its activity.
“We do not believe that there has been an increase in activity, but that since a swarm was registered on January 27, it rises the final number of earthquakes”, highlights Itahiza Domínguez, a seismologist from the National Geographic Institute (IGN). “In general, the activity remains the same,” he points out. In the last month, according to the data extracted from the IGN website, 68 earthquakes have occurred in that area, of which 63% occurred on January 27, coinciding with a swarm in the area. Which, however, has not been the first. “We have had it on other occasions,” recalls Domínguez. In fact, it also happened on September 15, 2022 and in April and October 2018.
They have been registered throughout the Canary Islands since the beginning of the year. 372 earthquakes, 111 on La Palma and between Tenerife and Gran Canaria, respectively; 96 in Tenerife and 11 in El Hierro. During the year 2022, the IGN registered 3,241 earthquakes, 1882 on La Palma, 714 on Tenerife, 404 between the capital islands and 39 on El Hierro.
The area not only arouses interest for having a sustained and continuous activity over time – about thirty earthquakes per month – but also for the magnitude that some of these earthquakes have reached. The strongest recorded in the area, and in the Canary Islands, occurred on May 9, 1989, with an earthquake of magnitude 5.2. In recent years there have been some “strong” earthquakes, such as in 2019, when a 4.4 magnitude earthquake shook the area or this same January 23 with a 3.4 earthquake.
Earthquakes in that area are usually detected about 30 or 40 kilometers deep and its strength does not usually exceed 3 mbLg. Although due to the difficulties to access the area and the lack of stations, the seismologists insist that the location may have a margin of error. To try to fill this gap in knowledge, IGN researchers have started a project to improve the earthquake detection as well as its location. “We have begun to install new stations,” explains Domínguez, who points out that the majority will be located in Gran Canaria as of March. “We are looking for locations, we have already made several trips”, highlights the researcher, who appreciates the collaboration of the Island Council, various town halls and even individuals to leave them space to place stations.
However, the ultimate reason for carrying out this investigation is to Solve the mystery of the origin of the earthquakes in the area. The enigma has gone unanswered for more than three decades, although many hypotheses have been put forward to try to explain it.
four theories
One of these theories correlates earthquakes with the existence of a fault that separates both islands and causes earthquakes. “It has been theorized that perhaps a structure of this type exists as an extension of the Atlas,” says Domínguez. But this theory does not have much support among the scientific community, and even less, after several analyzes of the area have found absolutely nothing. Among other things, as Domínguez explains, “because the distribution of earthquakes is not linear,” as usually happens in areas separated by a fault. Skeptical is also the IGN volcanologist, Stavros Meletlidis, who affirms that, if so, “we should have found it, because to generate earthquakes of that magnitude it would have to be quite large,” he highlights.
Another of the theories that the researchers are considering is the one that considers that the earthquakes are generated by the weight changes between the buildings of Tenerife and Gran Canaria that, in addition, are “one on top of the other”. It would be, as the IGN explains, a relative movement of approximation between the two islands due to the dismantling process of Gran Canaria and the growth of Tenerife and that could explain the existence of this seismicity. “But if that were the case, this would also have to happen on La Gomera and we are not seeing it,” says Domínguez.
Then there is one of the most famous, that of the Enmedio volcano, the name with which the area has been popularly called. Between both islands rises an underwater colossus, 470 meters high, one of the largest volcanoes in the Canary Islands under the sea. The structure was discovered shortly after the strongest earthquake that the Canary Islands have suffered in its recent history. that of 1989. Scientists set out to try to discover what had caused such terrestrial movement. From that expedition came the first “photograph” of the volcano made by the Spanish Institute of Oceanography (IEO) in 1990 and, later, it began to be related to seismic movements.
This last theory explained that between the two islands there is a hot spot where the magma “has an easier way out” because the oceanic crust is thinner. That would explain why there are so many “little cones” around the enmedio volcano and the very existence of the great colossus that rests on three and a half kilometers of land at its base (the size of Puerto de la Cruz). But this theory also raises doubts. “We do not believe that it is magmatic activity because the earthquakes that we see are not intense or in the form of a swarm, as would be expected if they were of this type of origin,” Domínguez emphasizes.
With the imminent start of the project, the researchers hope to find answers, which in two or three years could finally solve one of the best-kept enigmas of the Canary Islands.
