The Tunnel Between Spain and Morocco Enters a Crucial Phase

By Pedro Canales

The construction of the Euro-African tunnel that will connect Spain with Morocco has entered one of its most delicate and decisive phases: resolving whether the present or future seismic activity recorded in the Strait of Gibraltar can be controlled; or whether the risk level is high enough to halt or cancel the project.

Of the two options initially considered in the 1980s, bridge or tunnel, after intense studies, experts opted for the underwater tunnel. Currently, it would be 42 kilometers long, stretching from its entrance (or exit) at Punta Paloma located in Tarifa (Spain), to its exit (or entrance) at Punta Malabata, west of Tangier (Morocco). The project includes two single-track tunnels, each 7.9 meters in diameter, and a service gallery with a 6-meter diameter.

Significant advances have been made in the technical aspects of the construction, and the machinery needed for its execution already exists. The German company Herrenknecht, until recently the world leader in the tunneling market, is involved, although it was recently surpassed by the Chinese company CRCHI, which built the largest tunnel boring machine currently in existence, with an 18-meter diameter and a weight of 10,000 tons. SECEGSA has already met with the German company, but does not rule out possible offers from China.

The final decisions of the governments, in this case of Morocco and Spain, have a strong scientific-technical component, but also a political one, as strategic and geopolitical calculations come into play.

The project has now fully entered the phase of measuring seismic activity in the Strait. The Spanish public company in charge of the project, SECEGSA, aims to lease or purchase four Ocean Bottom Seismometers (OBS) for the work to be carried out by the Geophysics Section of the Royal Navy Observatory (ROA) in the Strait area. Ten years ago, both organizations used three seismographs that operated on the seabed for nine months, with inconclusive results. The results of that study showed little or no seismic activity, and the earthquakes detected were below 3.0 on the Richter scale.

Meanwhile, more recently, during the meetings of the Hispano-Moroccan Joint Committee in 2023, both countries committed to “relaunch and update the Fixed Link project through the Strait of Gibraltar.” For Madrid and Rabat, the Link was of “strategic importance,” which renewed seismic studies.

For Spanish scientist Juan José Dañobeitia, a member of UNESCO’s Tsunami Resilience Section, “the Gibraltar area has moderate seismicity,” though “earthquakes are recorded almost every day.”

The National Geographic Institute, under the Ministry of Transport, monitors the seismic activity recorded in the Strait area and predicts possible short-term earthquakes and their intensity. The Gulf of Cádiz, the Strait of Gibraltar, the Alboran Sea, and the Gulf of León all experience continuous seismic activity. Meanwhile, the scientific portal Volcano Discovery provides a detailed minute-by-minute list of earthquakes in the western Mediterranean. Between September 9 and 16, 169 earthquakes were recorded, including 26 on September 16 alone.

Indeed, statistics confirm that “seismic activity” in the Strait of Gibraltar, as scientist J. Dañobeitia states, “is moderate and permanent,” but specialists never rule out the remote but possible occurrence of higher-magnitude earthquakes or large-scale earthquakes in areas of the Atlantic Ocean near the Gulf of Cádiz, which could potentially cause tsunamis.

So far, no detailed studies have been conducted on the effects a tsunami could have on the Euro-African Tunnel in the Strait. Researchers from the Spanish National Research Council (CSIC) have determined that five tsunamis have occurred in the Gulf of Cádiz in the past 7,000 years, due to faults that mark the boundary between the European and African tectonic plates. Perhaps the most famous was the one in 1755, associated with the Lisbon earthquake, which caused large floods on the coasts of Spain, Portugal, and Morocco.

UNESCO’s Tsunami Early Warning Department, part of the Intergovernmental Oceanographic Commission where the aforementioned Spanish scientist Juanjo Dañobeitia works, has initiated the expansion of the tsunami early warning system in southwestern Europe and the Mediterranean Sea, based on an experiment conducted fifteen years ago with the early warning laboratory located in the deep waters of the Gulf of Cádiz. A network of interconnected sensors stretching hundreds of kilometers will detect earthquakes, measure their magnitude, and activate the necessary preventive measures.

The Euro-African Tunnel megaproject is situated in this context, and technical experts and scientists are on permanent alert, although the final decisions lie with the governments.