Coupling at Mauna Loa and K̄ılauea by stress transfer in an asthenospheric melt layer

The eruptive activity at the neighbouring Hawaiian volcanoes, Kı̄lauea and Mauna Loa, is thought to be linked1–3, despite both having separate lithosphericmagmatic plumbing systems. Over the past century, activity at the two volcanoes has been anti-correlated, which could reflect a competition for the same magma supply1,2. Yet, during the past decade Kı̄lauea and Mauna Loa have inflated simultaneously3. Linked activity between adjacent volcanoes in general remains controversial4–6. Here we present a numerical model for the dynamical interaction between Kı̄lauea and Mauna Loa, where both volcanoes are coupled by pore-pressure diffusion, occurring within a common, asthenospheric magma supply system. The model is constrained by measurements of gas emission rates7,8, indicative of eruptive activity, and it is calibrated to match geodetic measurements of surface deformation at both volcanoes, inferred to reflect changes in shallow magma storage. Although an increase in the asthenospheric magma supply can cause simultaneous inflation of Kı̄lauea and Mauna Loa, we find that eruptive activity at one volcano may inhibit eruptions of the adjacent volcano, if there is no concurrent increase in magma supply. We conclude that dynamic stress transfer by asthenospheric pore pressure is a viable mechanism for volcano coupling atHawai‘i, and perhaps for adjacent volcanoes elsewhere. An understanding of the processes responsible for the spatiotemporal distribution of volcanic activity is of global significance (Fig. 1). Its relevance was illustrated recently by the eruption of Ejyafjallajökull Volcano, Iceland, and associated speculation about the increased likelihood of a subsequent and related eruption at nearby Katla Volcano9. Global analyses indicate that the number of eruptions at volcanoes spaced closer than 200 km and erupting within days of each other increases significantly (approximately 4 standard deviations above the average)4,5. This is commonly attributed to stress transfer due to earthquakes or aseismic fault displacements10, and requires that both volcanoes are in a critical state and primed for activity5. Global positioning system (GPS) records for Mauna Loa and Kı̄lauea (see Methods), which are locatedwithin a distance of a few tens of kilometres from each other, reveal that Kı̄lauea, which was actively erupting, and Mauna Loa, which has not erupted since 1984, inflated concurrently during the past decade. This raises the questions of whether and how both volcanoes might be dynamically connected1–3, and if an eruption of Mauna Loa could bemore likely in the near future. Volcanism in Hawai‘i is the consequence of hot upwelling mantle and partial melting at depths >80 km, centred approximately 20 km south of Kı̄lauea11. Melt segregation by compaction of the asthenospheric partial melt zone12 may result in porous