hide
Free keywords:
-
Abstract:
Regions with complex topography display a variable degree of deformation during seismic and volcanic events. In the Reykjanes Peninsula rift, both extension and strike-slip motion result from its highly oblique angle with respect to the plate opening, leading to NE- and N-striking structures, including eruptive fissure swarms, tensile fractures, normal faults and strike-slip faults. Structural domains have been explained by factors like tectonomagmatic cycles or proximity to rift axes. However, pre-existing topographic gradients were not previously considered relevant for the resulting fracture network of the area, as suggested by studies at other sites.
Following a period of uplift in the Svartsengi volcanic system, a 2-meter-deep graben formed in November 2023 due to a ~15-km long dike intrusion. In this work, we use high-resolution photogrammetric data from before and after this event to explore how Mount Thorbjorn, situated on the western part of the graben, responded to this deformation event. A Digital Elevation Model (DEM) difference map suggests tilting of the mountain towards the east and reactivation of pre-existing faults. Comparison of orthophotos before and after the event revealed new surface fractures, many corresponding to reactivated buried discontinuities, mainly expressed as normal motion and with fissures showing opening. Statistical analyses were used to test the topographic controls on the resulting faulting pattern, and sandbox analogue experiments helped better understand the process. Preliminary results suggest that the distribution of the fractures is influenced by topography, with denser patterns observed in higher elevation areas, and changes in their strike due to surface adjustments.
