Faulting and crater development controlled by pre-existing topography - evidence from drone and satellite observations during the 2021 Cumbre Vieja eruption

Volcanic terrains host complex and commonly steep morphologies and are often also subject to tensile and shear faulting episodes. Previous studies demonstrated that strike slip and dip slip faults deflect at topographic highs and may locally diverge to develop multiple fault branches with varying strike and dip directions. Although fault deflection is associated with dike-related faults, a direct link to the positioning of eruption craters could not be established yet. Here we show that the Cumbre Vieja eruptions occurred in a complex pre-existing topographic and structural environment that affected fault development and evolution of eruption vents. 

We investigate available satellite radar data from the CosmoSkymed and TerraSAR-X missions, to track the temporal and spatial evolution of summit craters and faults. We find that summit craters are closely aligned in a direction NW-SE and developing a nested structure. We also conducted repeat drone measurements to acquire close-range optical images of the summit and nearby flanks. Results allow an in-depth analysis of the morphology of craters and the geometry, traces and throws of faults. We find that in late stages of the eruption important tensile faults evolve, and deflect at pre-existing topographic highs. We further find that these faults are developing complex sinkholes and secondary features due to their burial by loose unconsolidated material (i.e. tephra), and that the faults converge again at topographic lows, with varying degrees of the slip or dilation tendency. We discuss the coalignment of these structures with crater alignments, and present results from analogue models aiming to better constrain the varying deflection of faults controlled by topography.