Scientific article reveals details of seismovolcanic crisis on São Jorge Island

A team of researchers from Portugal, the United Kingdom and Spain has just revealed in an article published in the journal Nature Communications that major geological faults can have a dual function: they can either facilitate the ascent of magma, or, on the contrary, prevent this upward movement and avoid volcanic eruptions, through a phenomenon of escape. According to the study, it was this dual function that caused magma to ascend from a point more than 26 kilometres deep and to halt this movement 1.6 kilometres from the surface, resulting in a “failed eruption” in March 2022 on the São Jorge Island, in the Azores. The data reveal that the volcanic complex known as the Pico do Carvão Fault Zone “underwent an uplift of six centimetres” which helps to illustrate the ongoing growth on the Azorean island. The study was led by the University College London and included the participation of the Instituto Dom Luiz (IDL).

“This study revealed that magma can rise rapidly and silently and also highlights the dual function assumed by geological faults, which can both be facilitators and allow the escape of volatile components that cause the magma to lose mobility,” explains Susana Custódio, researcher at the IDL and lecturer at the Department of Earth Sciences and Energy (DCTE) of the Faculty of Sciences of the University of Lisbon (Ciências ULisboa), who participated in the study on the 2022 seismic crisis.

The conclusions of the study were published in the journal Nature Communications under the title “Fault-mediated magma propagation and triggered seismicity revealed by the 2022 São Jorge Azores unrest”. The researchers used as their working basis different types of data relating to the seismo-volcanic crisis, which were recorded with greater density from 19 March 2022 and which extended over the following months, during which tens of thousands of low-magnitude earthquakes were observed.

Reports indicate the fear of local populations – but fortunately, the worst-case scenario did not materialise. And the study now published in Nature Communications helps to point to potential reasons for what happened on the Azorean island. “This was a discreet intrusion,” said Stephen Hicks, a researcher at University College London and lead author of the scientific paper, in a statement. “The magma moved rapidly through the crust, but much of its journey was silent, which makes it difficult to predict whether an eruption will occur,” the researcher added in the statement.

The data collected by the team of scientists made it possible to determine “a vertical, laminar intrusion of magma” that is thought to have come from a point 26.5 kilometres deep and, in about three days, stopped underground, but already in the upper crust. “Much of this ascent occurred with reduced seismic activity, with most earthquakes being recorded only after the magma’s ascent had stopped,” the consortium of researchers’ statement emphasises.

A few days after the first signs of the seismic-volcanic crisis, researchers from the IDL travelled to the Azores to, with the support of local authorities, install seismometers and satellite positioning receivers (GNSS) to ensure the collection of data from across the island in the following months. The data recording also included seismometers (in some cases ocean-bottom) from the Natural Environment Research Council of UK (NERC) and networks managed by the Instituto Português do Mar e da Atmosfera (IPMA) and the Centre for Seismo-volcanic Information and Surveillance of Azores(CIVISA).

The participation of the IDL was ensured by researchers from the Ciências ULisbon hub as well as from the University of Beira Interior (UBI) and the Lisbon School of Engineering (ISEL). In addition to Susana Custódio, Virgílio Mendes also took part in this study as a researcher at the IDL hub at Ciências ULisboa.
“Typically we associate seismicity with intrusion, but in this case the seismicity was different because it was peripheral in relation to the intrusion,” explains Susana Custódio.

According to the study now published, the magma was halted due to a possible escape of the liquid and gaseous components to an adjacent segment of the geological fault where the ascent was occurring. The escape of the volatile components ended up “facilitating adjacent seismicity (to the site of the intrusion) and prevented an eruption from occurring,” says Susana Custódio.

“There could have been a larger earthquake, but fortunately that did not happen and we only had tens of thousands of low-magnitude earthquakes.”

The study now published was funded by the European Research Council (ERC), the Foundation for Science and Technology (FCT), the Regional Government of the Azores, the Natural Environment Research Council (NERC), United Kingdom, and the State Research Agency (AEI), Spain.

The study, which was led by the University College London, part of the University of London, United Kingdom, was carried out with strong participation from Portuguese entities: In addition to the IDL, the University of Lisbon, the University of the Algarve, Polytechnic Institute of Lisbon, University of Beira Interior, Azores Seismic and Volcanic Surveillance and Information Centre (CIVISA), Portuguese Institute for Sea and Atmosphere (IPMA), AIR Centre and C4G also took part in the project. From the United Kingdom, the Universities of Manchester and Cardiff participated, as well as the University College London. The National Council for Scientific Research (CSIC) also contributed to the research.