Sandra Hahn

Research Interests

My primary research interest is the application of magnetic methods in archaeology. This spans from the use of magnetometer prospection to discover and investigate archaeological sites, the reconstruction of their occupation histories through archaeomagnetic dating, to comprehend magnetic anomalies by integrating approaches from palaeo-, environmental-, soil- and rock magnetism. By combining these techniques, I aim to address unresolved questions in, improve our understanding of subsurface features, and help bridge the interpretative gap between magnetometer survey data and the results of archaeological excavation.

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Understandig magnetic anomalies in magnetometer prospecting in archeology

Magnetometer prospecting is one of the most widely used geophysical methods in archaeology, allowing for the detection and mapping of subsurface features of potential archaeological origin through recorded spatial variations in the geomagnetic field. I have successfully applied high-resolution magnetometer surveys to archaeological sites across three continents – from identifying the lost city wall of Fara in Iraq to revealing the interior of burial mounds in Artanish in Armenia. The various case studies highlight both the immense potential of magnetometry to uncover unknown archaeological features and the interpretative challenges posed by the resulting magnetic anomalies. In my research, I address the complexity of the various aspects in magnetometer prospecting: from surveying practice, including the testing of new data-acquisition strategies and processing techniques, to the analysis of magnetic signals and the simulation of magnetic anomaly demonstrating the non-trivial relationship of the source-specific parameters as well as the geomagnetic field. I further expand this approach by integrating soil, rock, and environmental magnetic analyses to better understand the origins of observed anomalies. Through this combined methodological framework, I aim to increase the reliability of magnetometer prospection and to improve the link between geophysical survey results and subsequent archaeological excavation.

Hahn, S. E., Fassbinder, J. W. E., Otto, A., Einwag, B., & Al-Hussainy, A. A. (2022). Revisiting Fara: Comparison of merged prospection results of diverse magnetometers with the earliest excavations in ancient Šuruppak from 120 years ago. Archaeological Prospection, 29(4), 623–635. https://doi.org/10.1002/arp.1878

Hahn, S.-E. (2025). Does the Geomagnetic Activity Affect Magnetic Anomalies? ArchéoSciences, 49-1(1), 509-512. https://shs.cairn.info/journal-archeosciences-2025-1-archeosciences-2025-1-page-509?lang=en.

Stele, A., Dragomirov, D., Hahn, S., Seisenbacher, C., Häußler, G., Linck, R. and Fassbinder, J.-W.-E. (2025). How Soil and Sediment Magnetism Contribute to the Understanding of Archaeological Magnetometry Data. ArchéoSciences, 49-1(1), 405-408. https://shs.cairn.info/journal-archeosciences-2025-1-archeosciences-2025-1-page-405?lang=en.

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Palaeosecular variation of the geomagnetic field

The Earth's magnetic field is subject to fluctuations in direction and intensity, collectively known as paleosecular variation (PSV). The relationship between reversal frequency of the polarity of the geomagnetic field, PSV amplitude, and dipole field strength remains a matter of ongoing debate. As a research assistant in the preceding project, I investigated the palaeomagnetism of volcanic rocks formed in Ethiopia between 15 and 30 million years ago which documented a local correlation between PSV and reversal frequency that was inconsistent with predictions from geodynamo simulations. Building on this work, I am now contributing to efforts to determine whether this apparent decoupling between PSV and reversal frequency reflects a local phenomenon or a global property of the geodynamo.To address this question, I am involved in a joint project aimed at acquiring new high-quality palaeomagnetic data from Tertiary volcanic rocks in Germany, including three major volcanic provinces—Vogelsberg, Rhön, and Lausitz—emplaced between approximately 37 Ma and 18 Ma ago.

Research Project:

• Palaeomagnetism of Tertiary volcanic rocks from Germany (Deutsche Forschungsgemeinschaft DFG - Projektnummer 517539177)

Chi, Y., & Lhuillier, F. (2025). Paleomagnetic secular variation of early middle miocene volcanics from Vogelsberg (Germany). Journal of Geophysical Research: Solid Earth, 130, e2024JB031007. https://doi.org/10.1029/2024JB031007

Publications