From single-point sensors such as optical fiber gyroscopes that are used in rotational seismology and sensor arrays such as fiber Bragg grating (FBG) arrays that are used for high-resolution seismic prospecting to integrated noise measurement over fiber deployed in-field, optical fiber sensors have certainly helped geophysicists and seismologists over the past two decades.

Fiber optic sensing technologies open new ways for observations of the full motion within the seismic wavefield with unprecedented precision. These include point observations of three translation vectors, three rotation axes and six components of strain as well as a single-axis strain distribution using distributed optical fiber sensors. Distributed Acoustic Sensors, for instance, allow for an extremely dense spatial sampling of the seismic wavefield with a relatively small logistical effort while Distributed Temperature Sensors enable continuous monitoring of subsurface geophysical features such as groundwater flow dynamics, permafrost conditions, and geothermal reservoirs' thermal behavior, offering valuable insights into environmental processes and geotechnical studies.

This session will cover technical aspects of fiber optic sensors and ranges from working principles and instrumentation designs to performance characteristics and deployment strategies to testing and calibration techniques for any kind of fiber optic sensing technology which is useful for the observation of geophysical parameters.

We welcome contributions to novel fiber optic measurement techniques that advance any observation of geophysical parameters. These include distributed sensing technologies for ground motion and temperature, integrated strain measurements using polarization analysis or ultra-stable lasers on telecommunication fibers, sensing array technologies used for recording seismic wave patterns, as well as technologies for point measurements of ground strain, rotation and displacement.

Invited speaker: Cecilia Clivati (INRIM, Italy)

According to the World Bank report “Natural Disaster Hotspots: A Global Risk Analysis”, about half of the world’s population lives in geographic regions prone to geohazards. In addition, fast rates of urbanisation and population growth increase the number of people settled in these high-risk areas. Therefore, monitoring for risk mitigations becomes increasingly important.

Additionally, the expanding exploitation of sustainable energy sources (such as geothermal energy) requires a comprehensive understanding of geological structures and stress conditions in the subsurface, in order to correctly assess the social and environmental impacts of subsurface-related operations.

Tackling challenges related to monitoring geohazards and sustainable usage of the subsurface requires obtaining large datasets in a cost-effective manner. Fibre optical cables offer a low-cost solution for sustainable monitoring of the subsurface. This session invites contributions showcasing the diverse applications of fibre optic technologies in addressing natural hazards related to earthquakes, volcanoes, landslides, glaciers, and tsunamis, as well as in the context of monitoring and managing geo-energy systems. The purpose of this session is to collect a broad range of showcases of the successful usage of fibre optic methods, highlight existing problems, and facilitate the discussion to resolve potential bottlenecks.

Invited speaker: Zhongwen Zhan (Caltech, USA)

Fibre optic sensing has proved to be efficient, even in harsh environments. The physical properties of the fibre glass and the protecting layers covering the fibre allow the cables to be deployed in difficult-to-reach locations (e.g., oceans, space, boreholes) and with extreme conditions (e.g., extreme temperatures, high pressures, acidic surroundings). Within these environments, fibre optic deployment also outperforms conventional sensors. This is due to the instrumental integrity and logistical advantages of fibre optic deployment, which allow for the acquisition of new data from regions and places that were previously difficult to access.

Despite the improvements, harsh environments also pose a challenge within the fibre optic sensing technology in many aspects, beyond material properties. Possible cable arrangements can be limited to the morphology of the region of interest (e.g., topography, ground coupling), which ultimately affects the quality of the data and the information that can be retrieved from it. Therefore, researchers in the field must also consider deployment, coupling, and cable arrangement to obtain as much information as possible from these unexplored regimes.

In this session, we welcome contributions that involve fibre optic sensing applications in extreme environments such as boreholes, deep ocean, acidic soil, space, and exoplanets. Contributions that explain the technical challenges of extreme locations, request solutions, and highlight the benefits of the existing, offering solutions for reducing costs and solving technical challenges, are particularly welcome.

Invited speaker: Marc-André Gutscher (Geo-Ocean, France)

Fibre optic sensing supported by the recent improvements in optical and atom interferometry, has enabled accurate and high-coverage sensing of the full ground motion wave-field and environmental parameters. Even in inaccessible domains or poorly instrumented environments, such as urban and submarine areas, a variety of signals have been successfully detected, ranging from microseism to teleseismic earthquakes, including volcanic events. The high sensitivity of the instrument is reflected in an increased number of possible applications. In this regard, the seismic source and wave-field characterization in harsh environments, the ocean bottom, the correction of tilt effects, as well as seismic ambient noise interferometry are just a few examples (some non-exhaustive examples).

However, the peculiarities of the acquired data demand the customization of signal processing techniques. If on the one hand traditional algorithms in geosciences are tailored to handle either the high spatial or the temporal resolution, on the other hand, the combination of high spatio-temporal acquisition throughput has fostered the widespread adoption of recent breakthroughs in Big Data analysis and advanced data analytics engines.

The session aims to highlight the innovation in classical methods/procedures and the recent technological advances on fibre optic sensing data analysis in any field of geosciences: seismology, volcanology, glaciology, geodesy, geophysics, natural hazards, oceanography, urban environment, geothermal applications, laboratory studies, large-scale field tests, planetary exploration, gravitational wave detection, fundamental physics.

Contributions dealing with processing, analysis and modelling for fibre optic sensing users are equally solicited. The overarching objective is to gather ingenious approaches in the application of the state-of-the-art algorithms in the geophysical field as well as recent cutting-edge techniques, such as High Performance Computing and Artificial Intelligence processes, with particular emphasis on Machine Learning models.

Invited speaker: Martijn Van den Ende (Université Côte d'Azur, France)

The widespread availability of fiber optic cables below the city streets provides a unique opportunity to leverage this existing infrastructure to improve our modern society’s resilience. The existing telecommunication fiber optic networks can be repurposed as massive arrays of sensors to investigate various aspects of our urban environment. Over recent years, many studies have proved that fiber sensing can be effectively utilized forvarious applications, including broadband seismic monitoring, near-surface property mapping, groundwater level monitoring, structural integrity assessment, and earthquake ground motion prediction for seismic hazards.

This session aims to bring together not only researchers, but also fiber optic network owners, photonics manufacturers, and experts in rock mechanics from both laboratory and mining contexts, all sharing an interest in the application of fiber optic sensing for enhancing societal resilience. Policymakers interested in exploring the use of telecommunication fiber cable for this purpose are also warmly invited to actively engage in the collaborative discussion.

We invite studies focusing on the utilization of telecommunication networks for all aspects of urban planning, from near-surface structure investigation to seismic monitoring, wave propagation, ground motion analysis, and finally, developing real-time monitoring and early warning systems for natural disasters. We also welcome contributions related to applications such as infrastructure resilience, including monitoring the health and integrity of civil structures, bridges, tunnels, highways, pipelines, dams, and other critical infrastructure. Furthermore, we are enthusiastic about further untapped capabilities or challenges of fiber optic networks for urban resilience purposes. If you have any other case studies or even witness challenges (e.g., signal saturation, fiber coupling problems, data confidentiality, and protection of personal life) on utilization of telecommunication fiber in diverse settings, including urban, rural, or coastal environments — both on land and underwater — with varying cable lengths, we encourage you to share your experiences/problems and possible technical/scientific solutions in this session.

Invited speaker: Hsin-Hua Huang (Academia Sinica, Taiwan)