USGS Volcano Notice - DOI-USGS-HVO-2023-12-31T10:08:31-08:00

Activity Summary:  Kīlauea volcano is not erupting. The seismic swarm that began south of Halemaʻumaʻu on December 29th ended yesterday coincident with the drop in inflation recorded at Sand Hill. Over the past day moderate rates of seismicity have returned to the southern summit region extending from the area south of Halemaʻumau crater and southwest to the Koʻae fault zone. Seismic activity is moderate in the upper East Rift Zone, but remains low along the Southwest Rift Zone. Unrest may continue to wax and wane with fluctuating input of magma to the area, and eruptive activity could occur in the near future with little or no warning. No unusual activity has been noted along the middle and lower sections of Kīlauea’s East Rift Zone.

Summit Observations:  Seismicity in the southern part of Kīlauea's summit region increased abruptly beginning at 1:10 p.m. on December 29, shortly after an increase in tilt at Sand Hill (see USGS HVO Information Statement — Kīlauea summit unrest | U.S. Geological Survey).  Locatable earthquakes averaged about 15 per hour during the height of this swarm with a peak of 27 per hour.  By noon yesterday, the average number of earthquakes dropped significantly to less than 5 per hour in coincident with the end of steep inflation at Sand Hill. In the past 24 hours earthquakes south of the caldera have continued at a lower rate than the previous day, with roughly 70 earthquakes, less than M2.5 occurring at depths of 1–3 km (0.5–2 mi). The increased seismicity began just south of Halemaʻumaʻu and the area has progressively widened to the southwest towards the Koʻae fault zone. Earthquakes are continuing with slight variations in rate and size in this region.  Periods of increased or decreased numbers of shallow earthquakes can be expected to continue during repressurization of the summit magma reservoir, which has been ongoing since the end of the September eruption. Seismicity has not reached the levels that immediately preceded recent summit eruptions at Kīlauea.

Yesterday around 11:00 a.m. HST, the rate of inflation at the Sand Hill tiltmeter, located just south of the caldera, decreased significantly and continues to record slight inflation.  The summit tiltmeter at Uēkahuna has recorded deflationary tilt over the past day, possibly starting a new DI event. Kīlauea's summit region remains at a high level of inflation; relative tilt is above the level reached prior to the most recent eruption in September 2023, and it is higher than at any time since the 2018 eruption.

Sulfur dioxide (SO₂) gas emission rates remain low. Field measurements indicated an SO₂ emission rate of approximately 80 tonnes per day on December 28, which was similar to measurements in October, November, and early December.

The strong swarm of earthquakes and rapid inflation that occurred south of the caldera on December 29 and 30 indicated that magma was being emplaced at relatively shallow levels.  This particular event led to an intrusion, but it is possible that similar events might lead to an eruption in the future. There are currently no signs of an imminent eruption at Kīlauea, but the volcano's summit region remains unsettled, with a high level of inflation and continued seismic activity. The onsets of previous summit eruptions have been marked by strong swarms of earthquakes caused by magma moving towards the surface 1–2 hours before the appearance of lava. This type of earthquake activity is not being detected at this time.

The information statement released on October 23, 2023, provides additional information and context related to recent unrest at Kīlauea's summit: https://volcanoes.usgs.gov/hans2/view/notice/DOI-USGS-HVO-2023-10-23T22:33:18-07:00

A map summarizing recent unrest around Kilauea’s summit (activity from November 11 to December 12, 2023) can be found here: https://www.usgs.gov/maps/december-12-2023-summary-map-unrest-kilauea-volcano

Rift Zone Observations:  Seismicity in Kīlauea's upper East Rift Zone increased over the past two days, with 44 events in the past 24 hours. Kīlauea's middle and lower East Rift Zones remain seismically quiet as does the Southwest Rift Zone.

We continue to closely monitor the summit and both rift zones, No unusual activity has been noted along the middle and lower sections of Kīlauea's East Rift Zone. Measurements from continuous gas monitoring stations downwind of Puʻuʻōʻō in the middle East Rift Zone—the site of 1983–2018 eruptive activity—have been below detection limits for SO₂, indicating that SO₂ emissions from Puʻuʻōʻō are negligible.

Hazard Analysis:  Levels of volcanic gases (sulfur dioxide and carbon dioxide) can remain locally hazardous even when Kīlauea is not erupting. Local concentrations of sulfur dioxide (SO₂) and/or hydrogen sulfide (H₂S) may persist in downwind areas, and residents may notice odors of these gases occasionally. Significant hazards also remain around Halemaʻumaʻu from crater wall instability, ground cracking, and rockfalls that can be enhanced by earthquakes within the area closed to the public. For discussion of Kīlauea hazards, please see: https://www.usgs.gov/observatories/hawaiian-volcano-observatory/hazards.

The Hawaiian Volcano Observatory (HVO) continues to closely monitor Kīlauea volcano.

Next Notice: HVO will issue daily Kīlauea updates. Additional messages will be issued as needed.