Ongoing (2015-) magma surge in the upper mantle beneath the Island of Hawaiʻi

“Surges” in magma supply from the mantle can lead to significant changes in eruptive behavior, thus their early identification is critical to long-term eruption forecasting. Here, we document and analyze two order-of-magnitude increases in seismicity in the upper mantle beneath southern Hawaiʻi between 2015 and 2020. We interpret the anomalous seismicity, which involved the rapid formation of new multiplets and a change in fault-plane solution orientations relative to pre-2015 events, as reflecting a substantial increase, or “surge” in mantle-derived magma, and we suggest that the intruded magma has been driving concurrent unrest at Mauna Loa, Kīlauea, and Lōʻihi Volcanoes through mechanical stress transfer.