“Mapping Kīlauea’s Magma Reservoirs” is a Research Spotlight by science writer Matthew R. Francis, published in Eos on 3 November 2026 (doi: 10.1029/2026EO260347).
It summarizes a high- resolution seismic tomography study of magma storage beneath the summit of Kīlauea volcano in Hawai‘i.
Researchers (Lin et al.) deployed a dense array of 1,815 small (nodal) seismometers in a roughly 12 km × 12 km mesh at Kīlauea’s summit.
They combined recordings of natural earthquakes with controlled seismic signals from a large vibroseis truck (“T-Rex”) that generates artificial vibrations. This hybrid passive and active- source approach produced millions of P- and S- wave arrivals.
Joint inversion of the travel- time data yielded 3- D models of P- wave velocity (Vp), S- wave velocity (Vs), and Vp/Vs ratio in the upper ~4 km (relative to sea level), on a 500 m grid. Resolution tests showed recovery of sub- kilometer to kilometer- scale structure.
The models clearly image two principal magma storage regions, each roughly 2 km across:
- One beneath Halemaʻumaʻu crater (in the main caldera).
- One beneath the south caldera.
Both appear as localized zones of reduced Vs (and moderately reduced Vp) with elevated Vp/Vs at depths of about 1- 3 km below sea level.
These anomalies are laterally distinct near the surface but appear to merge into a broader low- velocity zone at greater depth. Higher- velocity rock surrounding them is interpreted as stronger intrusive complexes that help confine the magma.
The seismic anomalies spatially match independent geodetic models of deformation sources, supporting the magma- reservoir interpretation.
Despite decades of monitoring, previous seismic images of Kīlauea’s summit plumbing lacked the resolution needed to sharply delineate individual reservoirs because of sparse sensor coverage.
The new hybrid dense- array approach overcomes that limitation and provides an improved framework for understanding magma storage and transport. The authors note that the methodology has already proved useful in other Kīlauea studies and could be applied at other active volcanoes.
The Eos article is a concise, accessible summary rather than the full technical paper; the original research contains the detailed models, resolution tests, and comparisons with geodetic data.
Kīlauea is one of the world’s most active volcanoes and the youngest on the Island of Hawaiʻi. It is in the shield- building stage of Hawaiian volcanism.
Written records begin around 1823 (after missionary William Ellis visited the summit), though oral histories and geologic evidence extend much further back.
Activity is predominantly effusive (fluid Hawaiian- style lava flows and fountains), with occasional explosive events.
Geologic records show frequent summit and rift- zone eruptions over millennia. Explosive phases occurred in the past, including a major event around 1790 (Keanakākoʻi Ash) that killed hundreds (part of a warrior party) and left preserved footprints in ash deposits
From the early 1800s until 1924, activity was nearly continuous at the summit caldera (Kaluapele), often featuring lava lakes in Halemaʻumaʻu. Major overflows filled parts of the caldera. Notable early events include the 1823 Southwest Rift Zone eruption and the 1840 East Rift Zone eruption.
20th Century Highlights
- 1924: A series of powerful steam explosions (phreatic) in Halemaʻumaʻu ejected rocks and ash; one person was killed. This ended the long period of continuous summit lava- lake activity.
- 1934– 1952: Quiet period (nearly 18 years of inactivity).
- 1952: Summit eruption in Halemaʻumaʻu (June– November) with lava fountains, ending the long quiescence.
- 1955: Lower East Rift Zone (Puna) eruption, first there since 1840, opened multiple vents and destroyed property.
- 1959: Spectacular Kīlauea Iki eruption with fountains up to ~580 m (1,900 ft).
- 1960: Kapoho eruption on the lower East Rift Zone destroyed the village of Kapoho.
- 1969–1974: Maunaulu (East Rift Zone) eruption, one of the longest and most voluminous flank eruptions of the prior 2,200 years.
- Other short summit and rift eruptions occurred through the 1960s- 1970s and early 1980s.
The Long Puʻuʻōʻō Eruption (1983– 2018)
This was Kīlauea’s longest and most voluminous historical East Rift Zone eruption (over 35 years). It began on January 3, 1983, with fissures that focused at Puʻuʻōʻō (and later Kupaianaha). It produced ~4.4 km³ of lava, covered >140 km², added new land to the coastline, and destroyed over 200 structures (including much of Kalapana in 1990). Activity was nearly continuous, with pauses of weeks to months.
From 2008 to 2018, a concurrent summit lava lake existed in a new vent within Halemaʻumaʻu, producing a persistent gas plume.
2018 Lower East Rift Zone Eruption and Summit Collapse
In May 2018, magma drained from the summit and Puʻuʻōʻō into the lower East Rift Zone (Leilani Estates area). This produced the largest and most destructive eruption in at least 200 years: ~1 km³ of lava, dozens of fissures, destruction of ~700 structures, and a magnitude- 6.9 earthquake. The summit caldera collapsed in stages (deepening Halemaʻumaʻu by hundreds of meters). The eruption ended in early August 2018.
Post- 2018 Activity (Reawakening)
After a quiet period, activity resumed:
- December 2020- May 2021: First post-2018 summit eruption in Halemaʻumaʻu (boiled off a water lake that had formed in the collapse pit).
- September 2021- December 2022 (or into 2023 in some accounts): Longer summit eruption filling more of the deepened crater.
- Additional short summit eruptions in 2023 (e.g., January, June, September).
- June 3, 2024: Brief (~8.5-hour) Southwest Rift Zone eruption.
- September 15- 20, 2024: Nāpau Crater eruption on the middle East Rift Zone (first ERZ eruption since 2018).
An episodic lava- fountaining eruption began on December 23, 2024, in Halemaʻumaʻu. By mid- to- late October 2026 it had produced at least 55 episodes of high fountaining (peaks exceeding 500 m / ~1,640- 1,770 ft in some episodes), with pauses of days to nearly two months.
Lava has raised the crater floor significantly (over 100 m in places) but remains contained within the caldera. Scientists use summit tilt (inflation, deflation) to forecast episode windows. As of early November 2026, activity continued with overflows and reinflation after episode 55 (October 17, 2026).
Kīlauea’s eruptions are closely monitored by the USGS Hawaiian Volcano Observatory. Patterns often involve magma storage in summit reservoirs (Halemaʻumaʻu and south caldera) that feed both summit and rift- zone activity. For the absolute latest status, check the USGS HVO website, as conditions can change rapidly.
High-Resolution Body-Wave Tomography of Kı̄lauea’s Summit Magma Storage System From a Dense Passive and Active Source Experiment
This paper presents the highest- resolution seismic images yet of the shallow magma storage system beneath Kīlauea’s summit.
The authors conducted a 37- day hybrid seismic experiment in May- June 2023 that combined a very dense array of nodal seismometers with controlled-source (vibroseis) signals.
Experiment Design
- 1,815 three- component nodal seismometers deployed in a ~12 times 12 km mesh across the summit and caldera.
- 396 vibroseis source positions using a large T- Rex vibroseis truck that generated controlled seismic vibrations.
- Combined with natural local earthquakes.
- Resulted in ~15 million P- and S- wave arrivals
Methods and Results
Joint inversion of the earthquake and active- source travel times produced 3- D models of:
- Compressional- wave velocity (Vp)
- Shear -wave velocity (Vs)
- Vp/Vs ratio
Models cover the upper ~4 km (relative to mean sea level) on a 500 m grid. Resolution tests confirm recovery of sub- kilometer to kilometer- scale features.
Key findings:
- Two principal magma storage regions, each ~2 km across:
- Beneath Halemaʻumaʻu crater
- Beneath the south caldera
- Both appear as zones of reduced Vs (and moderately reduced Vp) with elevated Vp/Vs at depths of 1- 3 km below sea level.
- The anomalies are laterally distinct at shallow levels but appear to merge into a broader low- velocity zone at greater depth.
- Surrounding higher- velocity rock is interpreted as stronger intrusive complexes that help confine the magma.
- The seismic anomalies spatially match independent geodetic (deformation) models of magma reservoirs, supporting the interpretation.
Previous seismic images lacked the resolution to clearly separate individual reservoirs because of sparse permanent station coverage.
This hybrid dense- array approach overcomes that limitation and provides a much sharper view of how magma is stored and potentially connected beneath the summit.
The authors note that the methodology can be applied at other active volcanoes.
The images show magma stored in two regions. One under Halemaʻumaʻu is consistent with hot, fractured rock that may contain magma and gases.
The second under the south caldera is more confined. They are separate near the surface but may link deeper. Higher- velocity rock around them acts as a mechanical boundary.
Journal: Journal of Geophysical Research
DOI: 10.1029/2026JB034515
First published: 15 October 2026, (Open Access)
Provided: Eos
Authors: Guoqing Lin, Steven Roecker, Roger Denlinger, Dan O’Connell, Ninfa Bennington, Elizabeth Vinarski, Ashton Flinders, Matthew M. Haney
Abstract
Imaging magma storage beneath active calderas requires resolving crustal structure at scales comparable to those of individual reservoirs. To identify potential reservoirs beneath Kı̄lauea, Hawai’i, we conducted a hybrid seismic experiment at its summit for 37 days in 2023 that combined more than 1,800 three-component nodal seismometers with 396 vibroseis source positions, yielding about 15 million 𝑃– and 𝑆-wave arrivals. Joint inversion of earthquake and active-source travel times yields three-dimensional models of 𝑉𝑝, 𝑉𝑠, and 𝑉𝑝/𝑉𝑠 within the upper ∼4 km beneath the summit relative to mean sea level, parameterized on a 500 m grid, within which the resolution tests demonstrate recovery of sub-kilometer to kilometer-scale structure. The models delineate two principal magma storage regions beneath Halema’uma’u and the south caldera, each on the order of 2 km across. Both reservoirs are expressed as localized zones of reduced 𝑉𝑠 and moderately reduced 𝑉𝑝 with locally elevated 𝑉𝑝/𝑉𝑠 at depths of 1–3 km below sea level. The anomalies are laterally distinct at shallow levels but appear to merge within a broader zone of reduced velocities at depth. Surrounding higher-velocity domains likely represent mechanically stronger intrusive complexes that confine magma storage. Spatial correspondence between seismic velocity anomalies and independently modeled geodetic deformation sources supports the interpretation that the imaged structures represent magma storage regions. These results demonstrate that dense nodal arrays combined with hybrid passive-active tomography can resolve reservoir-scale structure at active volcanoes and provide an improved framework for interpreting magma storage and transport beneath Kı̄lauea.
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