Present-Day Architecture of the Magma Plumbing System beneath Hekla Volcano from Magnetotelluric Imaging

Hekla volcano, one of Iceland’s most active stratovolcanoes, is characterised by very short eruption precursory times and a complex tectonic setting at the intersection of the South Iceland Seismic Zone (SISZ) and the Eastern Volcanic Zone. Despite its frequent activity, the geometry and connectivity of the magmatic system beneath Hekla remain poorly constrained. In this study, we use three-dimensional magnetotelluric (MT) imaging to investigate the electrical resistivity structure beneath Hekla and its implications for magma storage and transport.

This study forms part of a newly funded project under the Research Ireland Frontiers for the Future Programme, with objectives to (i) characterise the present-day structure, depth extent, and geometry of the magmatic system beneath Hekla, (ii) identify low-resistivity zones that may serve as proxies for partial melt and magma migration pathways, and (iii) assess potential magmatic interconnection between Hekla and the adjacent Torfajökull volcanic system, including the possibility of a shared deep magma source. Preliminary 3D inversion results based on MT data from 20 broad-band stations reveal two principal conductive features. Shallow (<2 km) N–S-trending conductive anomalies are observed beneath and southeast of the central edifice. These features are interpreted as groundwater-saturated fracture networks associated with regional faulting within the SISZ. At greater depths (approximately 6–24 km), a pronounced NW–SE-oriented conductive body is imaged beneath Hekla, oriented obliquely relative to the ENE-trending surface fissure swarm. This deeper anomaly is interpreted as a magma storage zone and may play a key role in controlling Hekla’s eruptive behaviour and rapid unrest development. In 2025, the MT network was expanded with data from over 30 additional stations, significantly improving spatial coverage and resolution. This contribution presents the newly acquired data and integrated 3D inversion results combining the new and existing datasets, providing enhanced constraints on the crustal-scale magmatic architecture beneath Hekla and its relationship to regional tectonic structures.