The origin of earthquakes, the secret that will be buried with the Castor
According to researchers, there were high magnitude earthquakes that normally occur at greater depths.
TarragonaThousands of tons of cement will begin to seal the Castor warehouse under the sea this spring, burying forever a mystery that no one has yet been able to solve: why did those earthquakes occur?
The intention of its promoters was to inject a maximum of 1.9 billion cubic meters of natural gas over six months, a quantity sufficient to guarantee the supply of this source of energy to all of Spain for 50 days. But after injecting gas for 15 days, more than a thousand small earthquakes occurred, which caused the Ministry of Industry to order the warehouse to close on September 26, 2013. Although this forced the promoters to pay millions in compensation, it is still unknown why the earthquakes occurred.
In March 2018, the Ombudsman published a report with the participation of technicians from the Official College of Geologists of Catalonia, as well as that of Civil Engineers, Canals and Ports and that of Environmentalists, which wanted to lay the foundations for an audit. The document denounced that "until now, the reason for the earthquakes is still a mystery that remains to be revealed."
Seven years have passed and other studies have been published on the subject, but none is definitive. "We cannot say that we are 100% sure of what happened," laments Víctor Vilarrasa, researcher at the Institute for Environmental Diagnosis and Water Studies (IDAEA). He is the author of one of the latest studies on the Castor, which he carried out together with technicians from the Institute of Marine Sciences and under the umbrella of the Higher Council for Scientific Research (CSIC).
One of the doubts that scientists had was that "at the depth of the gas reservoir, low-magnitude earthquakes could be expected, since the rocks are relatively soft and when they break, they do not do so abruptly, but rather deform progressively." greater rigidity and release more energy when they break."
The hypothesis of a second fault
The Castor warehouse is located on the Amposta fault, which was already expected to move after the gas injection, because "historically it has had many displacements." However, the earthquakes caused by this movement should be mild. However, the researchers found another much deeper fault connected to the Amposta fault, and their conclusion is that, when they injected gas, they increased the pressure and caused the movement of the Amposta fault, which was "accumulating displacements and ended up destabilizing the deeper fault."
Preparing this study, published in April 2021, was not easy. "They denied us data that is theoretically public," denounces this researcher. "In addition, the two seismographs that were placed in the sea to detect possible earthquakes did not work," he concludes.
A geologist who knows the area and the Castor project very well, but who prefers to remain anonymous, also suggests the possibility that the reservoir was actually already full of gas and oil, and that when the gas was injected it ended up exploding. He is absolutely convinced that "those who carried out the studies to make the wells know perfectly well what happened", since before an operation of this magnitude many surveys are carried out and all kinds of consequences are foreseen. "They force us to speculate because there is no transparency," he criticises.
