HT and Faculty of Science Install Seismic Wave Detection Instrument

As part of the strategic City Changer project, launched early last year, Hrvatski Telekom, in collaboration with Dubrovnik-Neretva County and the Faculty of Science in Zagreb, deployed a distributed acoustic sensing (DAS) instrument along a 17-kilometer fiber optic route from Gruda to Vitaljina. DAS has been quickly adopted in many geophysical applications.

DAS sensors convert telecommunications or newly installed optical cables into sensor arrays that measure strain or strain changes and can be used to track seismic signals and low-frequency mechanically and thermally induced stresses. Recent advances in DAS data analysis have been reflected in applying early warning systems for earthquakes or tsunamis, with data collected from fiber optic cables placed on land or the seabed.

"City Changer places telecom infrastructure in the focus of society's digital transformation, fostering co-creation of diverse solutions that connect key stakeholders, public and private sectors, academia, and citizens. The project emphasizes strategic partnerships that drive impactful solutions in areas that contribute strongly to societal well-being and safety. Building community resilience to natural disasters and hazards is, without a doubt, one such area. The collaboration between Hrvatski Telekom, the Faculty of Science, and Dubrovnik-Neretva County is a prime example of this," said Renato Totić, Strategic Business Project Lead at Hrvatski Telekom.

Fiber optic cables laid underwater are optimal for regions where earthquake sources or fault lines lie on the seabed. In addition to earthquake detection and analysis, submarine fiber optics can also support other geophysical measurements, such as monitoring ocean currents.

"DAS technology enables the use of optical cables as a network of sensors for seismic wave detection, turning them into densely distributed seismometers without requiring additional components. The principle relies on sending a series of laser pulses through the optical fiber and recording the return time of the naturally dispersed signal. This method enables continuous real-time measurements along the entire optical fiber length, even at distances exceeding 50 kilometers. The first earthquake recordings through this method demonstrate the vast potential of DAS technology not only in geophysics and seismology but also in a wide range of other applications," said  Josip Stipčević from the Faculty of Science.

The deployment of this system is a significant step forward in improving seismic monitoring in the region. Hrvatski Telekom, one of the first telecoms in Europe, is thus enhancing community safety by repurposing its optical infrastructure, giving it a new application dimension and adding overall value.