Moderate-magnitude earthquakes induced by magma reservoir inflation at Kilauea Volcano, Hawai'i

Although volcano-tectonic (VT) earthquakes often occur in response to magma intrusion, it is rare for them to have magnitudes larger than ∼M4. On 24 May 2007, two shallow M4+ earthquakes occurred beneath the upper part of the east rift zone of Kilauea Volcano, Hawai'i. An integrated analysis of geodetic, seismic, and field data, together with Coulomb stress modeling, demonstrates that the earthquakes occurred due to strike-slip motion on pre-existing faults that bound Kilauea Caldera to the southeast and that the pressurization of Kilauea's summit magma system may have been sufficient to promote faulting. For the first time, we infer a plausible origin to generate rare moderate-magnitude VTs at Kilauea by reactivation of suitably oriented pre-existing caldera-bounding faults. Rare moderate- to large-magnitude VTs at Kilauea and other volcanoes can therefore result from reactivation of existing fault planes due to stresses induced by magmatic processes. Key Points Unusual M4+ earthquakes at Kilauea triggered by ongoing summit inflation Summit inflation and lateral faulting consistent with seismic and geodetic data Reactivation of faults by magmatic stresses explain large VTs at volcanoes