Volcanotectonic interactions between Mauna Loa and Kilauea: Insights from 2-D discrete element simulations

Numerical simulations using the discrete element method (DEM) are carried out to examine the dynamics and internal deformation of overlapping volcanoes constructed upon a weak décollement horizon, as analogs to the Kilauea–Mauna Loa system of volcanoes in Hawaii. Employing a frictional rheology, the DEM simulations capture much of the complex deformation behavior of Mauna Loa and Kilauea volcanoes, here referred to as the primary and secondary edifices, respectively. The models demonstrate incremental displacements of the outer flanks of the volcanoes and concurrent summit subsidence, leading to characteristic low slopes and inward dipping strata. Slip discontinuities that develop within the piles define steeply dipping normal faults along the upper flanks and beneath the edifice summits, that accommodate subsidence and flank spreading. Edifice overlap influences dynamic behavior significantly; even small topographic perturbations restrict the internal deformation and spreading of the confined flanks. The degree of buttressing depends on the relative positions of the two edifices. If the secondary edifice grows high upon the flanks of the primary edifice, outward spreading of the underlying flank is enhanced; if the secondary edifice is built low upon the primary flanks, spreading of the underlying flank is effectively prevented, or possibly reversed. Furthermore, as the second edifice grows, it subsides into the underlying flank, partitioning it into a mobile downslope region entrained by spreading of the second edifice, and a comparatively stable upper flank region. These results suggest that much of the mass of Kilauea volcano may lie deeply buried within the underlying flank of Mauna Loa, while older Mauna Loa rocks may lie far from their source beneath the mobile flank of the younger volcano.