INESC TEC researchers detected long-distance seismic activity in Madeira

The team led by INESC TE researcher Orlando Frazão detected, for the first time, long-distance seismic activity on Madeira Island, using Distributed Acoustic Sensing (DAS) technology.

The team that also features Susana Silva, Catarina Monteiro, and Cristina Cunha, installed an HiFi – Distributed Acoustic Sensor at EMACOM’s Submarine Cable Station at the Amparo site (Madeira) to monitor seismic activity. The HDAS equipment, provided by the University of Alcalá, Spain, was installed on a fibre of the EllaLink cable to measure and record strain along the 50 km of optical fibre. The collaboration with FCCN ensured internet connectivity from the island to the mainland – a process that benefited from the vital support provided by Jaime Dias and António Carlos Sá (Systems Administration Service), namely in terms of data storage.

The INESC TEC team collected, processed, and analysed the data, in collaboration with Hugo Martins from the IO-CSIC in Madrid, Spain. Said analysis, carried out between January 31 and February 10, 2023, showed different events – including a telesism with a magnitude of 7.8 on the Richter scale that occurred in Turkey on February 6, 2023 (as depicted in Figure 1).

Figure 2 displays the wavenumber spectrum as a function of the distributed acoustic detection frequency, illustrating the propagation of the earthquake through oceanic and seismic waves in the ocean. This earthquake was not felt by the population, nor did it cause any damage, but it was detected by seismic stations in Madeira, Porto Santo, and the Canary Islands. The HDAS technology employed in these tests also proved capable of detecting other long-distance and local events of lower magnitude. This marks a significant advance in seismic monitoring capabilities through DAS technology, using existing submarine cables. Furthermore, the technology shows high potential in the fields of oceanography and cetology, and its effectiveness in structural monitoring of underground fibre optic cables has already been demonstrated.

INESC TEC and the other institutions are part of the European project SUBMERSE, which aims to install DAS and SoP equipment in Portugal, Greece, and Norway to store, process, and analyse geophysical data.