GEOPHYSICAL IMAGING OF STOCKHOLM’S SUBSURFACE AT A MUNICIPAL SCALE – IMPLICATION FOR USE AND PLANNING OF ITS UNDERGROUND URBAN SPACE

19th WORLD CONFERENCE OF THE ASSOCIATED RESEARCH CENTRES FOR THE URBAN UNDERGROUND SPACE, Belgrade, Serbia, November 4-7, 2025. (Paper No: 2.18.120,  pp. 432-440)

 

АУТОР(И) / AUTHOR(S): Emmanuel Alofe, Mehrdad Bastani, Ari Tryggvason

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DOI:  10.46793/ACUUS2025.2.18.120

САЖЕТАК / ABSTRACT:

The absence of the underground space and its usage in the current Stockholm city plan raises concerns about the urban underground space planning culture of Sweden. This issue becomes even more alarming because it is unclear, both in the literature and among practitioners, whether a map of Stockholm’s subsurface exists at a municipal or district scale for planning purposes, despite the extensive use of the subsurface. Therefore, we processed airborne geophysical datasets, namely magnetic and very-low-frequency (VLF) electromagnetic, acquired over Stockholm municipality, to produce municipal-wide geophysical signature maps of the underground infrastructures in Stockholm. Stockholm’s underground metro, a significant infrastructure across the city, served as a guide for the geophysical imaging, which included other underground infrastructures with similar geophysical signatures. Two maps were produced: the VLF electrical current density map, which was derived using a transformation from its raw data; and the magnetic anomaly map, which shows the residual between measured and upward continued (UC) fields. Our results show that Stockholm’s central area, known as the innerstaden in Swedish, has a significantly higher infrastructure density than other areas, necessitating a rethink for further underground development in this area. We also find geophysical signatures, typical of major infrastructures, beneath the development focus areas proposed in the city plan outside the innerstaden area, which should be incorporated into the developments in these areas. Although our results are presented as 2D maps and are thus limited in the vertical dimension, the transformation algorithms and filters applied during processing were in 3D. Inspite of the results’ dimensionality, they provide preliminary insights into the subsurface of Stockholm municipality at a resolution that may be suitable for strategic planning decision at a municipal scale. These results could be further developed into 3D models for a more holistic municipal-scale planning of Stockholm’s underground space. 

КЉУЧНЕ РЕЧИ / KEYWORDS:

magnetics, VLF, underground, Stockholm, planning

ПРОЈЕКАТ / ACKNOWLEDGEMENT:

We express our gratitude for the research grant (grant no: 2021-00106) from the Swedish Research Council Formas, within the National Research Program for Sustainable Spatial Planning (Nationella forskningsprogrammet för hållbart samhällsbyggande), which made this study possible. We also thank the Swedish Geological Agency (Sveriges geologiska undersökning, SGU) for supplying the geophysical datasets used in this study. We would also like to extend our appreciation to the anonymous reviewers for their valuable feedback.

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