LAUSR

The deep magmatic architecture of the Hawaiian volcanic system is central to understanding the transport of magma from the upper mantle to the individual volcanoes. We leverage advances in earthquake monitoring with deep learning algorithms to image the structures underlying a major mantle earthquake swarm of nearly 200,000 events that rapidly accelerated after the 2018 Kīlauea caldera collapse. At depths of 36 to 43 kilometers, we resolve a 15-kilometers-long collection of near-horizontal sheeted structures that we identify as a sill complex. These sills connect to the lower depths of Kīlauea’s plumbing by a 25-kilometers-long belt of seismicity. Additionally, a column of seismicity links the sill complex to a shallow décollement near Mauna Loa. These findings implicate the mantle sill complex as a nexus for magma transport beneath Hawai‘i and furthermore indicate widespread magmatic connectivity in the volcanic system. Description A magmatic nexus The island of Hawai‘i is shaped by its well-known volcanoes, Mauna Kea, Mauna Loa, and Kīlauea. Although Kīlauea is currently by far the most active, the other volcanoes could still erupt as well. Wilding et al. used more than 200,000 seismic events to map out the geometry of the magma feeding into these volcanoes at a 40-kilometer depth (see the Perspective by Flinders). The magma forms a sill complex that connects Kīlauea and Mauna Loa, and there is some evidence of connection to Mauna Kea. The observations suggest far greater underground connections between the volcanoes and provide an interesting insight into magma transport. —BG Interacting magmatic sills at about 40-kilometer depth under the island of Hawai‘i feed into multiple different volcanoes.