One day there will be an earthquake forecast. It’s just not known when
Unlike the sky, the Earth’s interior is not transparent. And that’s why a seismologist like Fernando Carrilho faces very different challenges from colleagues from other departments at the Portuguese Institute of the Sea and the Atmosphere (IPMA), who can relate the previous day’s forecasts to the clouds they see on the horizon. “There are earthquakes originating from depths of 10, 20, 100 kms or more… and the existing technologies do not allow us to know what is happening in these places”, explains the head of the Geophysics Division at IPMA.
In the 1970s, several scientists tried to find a way to predict earthquakes — but that first impulse has lost much of its force after 20 years. “If I say that there is going to be an earthquake of magnitude 3 or 4 in Lisbon, I could be correct (due to the characteristics of the region). But I cannot know when this earthquake will occur. A forecast must have an instant of occurrence, location and magnitude, otherwise it is not an earthquake forecast”, adds Fernando Carrilho.
The expectation of the last century has failed and recent technological advances have not helped much either. “Tomography scans of the Earth’s interior are already being carried out, but the images do not have much resolution, in addition to requiring very expensive and time-consuming scientific campaigns”, explains Rui Moura, professor at the Faculty of Sciences of the University of Porto.
Given the difficulty in collecting data, some scientists even tried to establish a relationship between earthquakes and changes in electromagnetic fields or radon gas emission. But these studies were also inconclusive. “There are several places with an increase in radon emissions and changes in electromagnetic fields that have not suffered earthquakes”, recalls Fernando Carrilho.
In the absence of a solution, efforts began to focus on mitigation. And Japan, with four thousand seismic stations and sensor networks in the Pacific, is the benchmark in this approach. Seismic waves travel across the ocean floor at speeds of four to seven kilometre per second, but sensor networks “go beyond them” by traveling at the speed of light allowed by fibre optics. Which gives you to issue alerts tens of seconds before the earthquake affects the archipelago, famous for its automation. “Even if it’s three seconds ahead, it makes a difference. It’s enough time to open doors, turn off the gas or for the elevators to stop in the right place automatically”, says Rui Moura.
Mexico and the US already have sensor networks — and there are plans for Portugal to join the “mitigation” club. The project has been developed by IPMA, Instituto de Telecomunicações and Instituto D. Luís, in the LEA consortium. The objective is to take advantage of the replacement of the ring of submarine telecommunications cables that link the continent, Azores and Madeira with sensor cables. Fernando Carrilho believes that the investment pays off, “even with a 10% increase in costs”.
The renovation will have to be completed by 2027, when the current cables expire. “The State Budget already provided for this investment, but it ended up not being approved. It is an urgent decision that will have to be taken soon”, concludes Fernando Carrilho.