High-Resolution Subsurface Geophysical Characterisation of Icelandic Volcanic Layering

Integrating geophysical techniques at two contrasting locations—fractured young lavas in southwestern Iceland and older layered basalts in eastern Iceland—constrains the structure and shear-wave velocity of the volcanic subsurface. The results show that relying on a single geophysical method often yields non-unique solutions that can obscure velocity profiles and overlook sharp structural contrasts. Findings from southwestern Iceland reveal that young, faulted ‘a‘ā flows have a complex architecture with shallow, eroded layers, resulting in a reduced Vs30. Conversely, older Miocene bedrock in eastern Iceland shows a well-layered, consolidated structure with a higher Vs30. We demonstrate that modelling Scholte waves from legacy marine seismic data can generate regional velocity models consistent with onshore measurements.