Insights into the 1976–2000 eruption episode of Whakaari/White Island, New Zealand: an eruption fuelled by repeated mafic recharge

Identification of Seismo‐Volcanic Regimes at Whakaari/White Island (New Zealand) Via Systematic Tuning of an Unsupervised Classifier

“…Whakaari hosts an active hydrothermal system in the upper ∼1 km of the vent fill, which strongly influences the local seismicity (Christenson et al, 2017;Giggenbach, 1987;Heap et al, 2017;Jolly et al, 2017Jolly et al, , 2018Nishi et al, 1996). Below the hydrothermal system, multiple magma storage regions are inferred at depths between 2 and 9 km (Cole et al, 2000;Houghton & Nairn, 1991;Kilgour, Moune, et al, 2021). Jolly et al (2017Jolly et al ( , 2018 detected repeating very long period (VLP) seismicity at ∼1-km depth and inferred this to be the top of a shallow magma storage zone, overlain by a magma carapace.…”

“…Whakaari is an andesitic‐dacitic composite cone 50 km north of the Bay of Plenty, in New Zealand's North Island (Figure 1). Over the last 50 years, the volcano has undergone episodes of intense fumarolic and degassing activity, including sudden explosive phreatic and phreatomagmatic eruptions, most recently in 2012/2013, 2016, and 2019 (Chardot et al., 2015; Jolly et al., 2018; Kennedy et al., 2020; Kilgour et al., 2019; Kilgour, Kennedy, et al., 2021; Kilgour, Moune, et al., 2021; Walsh et al., 2019), small lava‐dome extrusion episodes and small‐scale ash‐venting events (Jolly et al., 2017, 2020). These episodes of elevated unrest and eruptions occur between quieter periods with little or no anomalous surface activity observed.…”

“…Whakaari hosts an active hydrothermal system in the upper ∼1 km of the vent fill, which strongly influences the local seismicity (Christenson et al., 2017; Giggenbach, 1987; Heap et al., 2017; Jolly et al., 2017, 2018; Nishi et al., 1996). Below the hydrothermal system, multiple magma storage regions are inferred at depths between 2 and 9 km (Cole et al., 2000; Houghton & Nairn, 1991; Kilgour, Moune, et al., 2021). Jolly et al.…”

“…The long‐term source of magmatic fluids (magma, gases, water vapor) at Whakaari derives from intrusions into the upper and middle crust at ∼1–9‐km depth (Jolly et al., 2018; Kilgour, Moune, et al., 2021). As deep magmatic fluids ascend into the upper conduit system, they form the first phase of unrest (Figure 2).…”

“…As deep magmatic fluids ascend into the upper conduit system, they form the first phase of unrest (Figure 2). These deep‐sourced fluids may be augmented by other magmatic fluids released by dehydration and crystallization of stalled magma bodies resident at very shallow levels (∼1‐2 km deep) (Kilgour, Moune, et al., 2021). Collectively, magmatic inputs interact with meteoric fluids that circulate within the hydrothermal system of the upper volcano (Christenson et al., 2017), generating a second phase of unrest.…”