(BIVN) – The elevated unrest to the south-southwest of Kīlauea’s summit prompted a detailed information statement from the USGS Hawaiian Volcano Observatory on Monday evening:

KĪLAUEA INFORMATION STATEMENT

Kīlauea volcano is not erupting. Elevated unrest to the south-southwest of Kīlauea’s summit has continued over the past 24 hours in association with an intrusive event that began in early October. Tremor was observed on seismic stations nearly island-wide today, from approximately 2:20 p.m. to 3:00 p.m., and was strongest at Kīlauea summit. No significant changes in ground tilt were observed during this tremor event. Unrest may continue to wax and wane with changes to the input of magma into the area. The summit of Kīlauea remains at a high level of inflation and eruptive activity at the summit is possible with little or no warning. No unusual activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone. The current Volcano Alert Level remains at ADVISORY. The current Aviation Color Code remains at YELLOW. This update summarizes recent observations and outlines possible scenarios.

RECENT OBSERVATIONS

The most recent eruption at Kīlauea summit ended on September 16, 2023. Following this eruption, seismicity and ground deformation remained at background levels until the first week of October. Rates of ground deformation then began to increase, especially in the region extending from the south caldera to the Koa‘e fault zone. A series of seismic swarms began in this region on October 4, 2023, peaking at more than 250 earthquakes on October 5. Magma did not reach the surface, and rates of seismicity and deformation diminished after October 5, suggesting an intrusion. Unrest has continued to wax and wane since then.

Overall inflationary ground deformation has continued intermittently with days-long periods of increased rates alternating with days-long periods of little or no ground deformation. In total, approximately 120 microradians of change have been recorded by the Sandhill (SDH) tiltmeter over the past three weeks. (Note: the SDH tiltmeter went offline on October 9 due to instrument maintenance and was reset; an offset was estimated from other geophysical measurements and added to the SDH time series to approximate deformation during this outage.) GPS and satellite radar data confirm that over 10 cm (4 inches) of inflation has occurred in this region since late September. At Kīlauea’s summit, the Uēkahuna (UWE) tiltmeter has shown more persistent but slower inflation, with approximately 20 microradians of change over the past three weeks.

Since October 5, intermittent seismic swarms have continued, varying from less than 20 events per day to more than 150 events on October 22. Generally, higher numbers of earthquakes coincided with times when the SDH tiltmeter showed increased rates of inflationary ground motion, from October 3-6, 16-18, and 21-23. Most of the earthquakes related to this unrest have been smaller than magnitude-2 and have occurred at depths of around 1–3 km (0.6–2 mi) below the surface. Seismic signals indicating magma movement, such as low-frequency tremor, have also been observed at Kīlauea summit stations, most recently on the afternoon of October 23, 2023.

A map of the recent intrusive activity is available here.

INTERPRETATION AND CONTEXT

These patterns of ground deformation and earthquakes indicate that a magmatic intrusion is occurring beneath the south-southwest region of Kīlauea’s summit. Numerous intrusions have been recorded here in the past, most recently in 2021 and 2015. In August 2021, an intrusion here occurred over about a week and was followed by an eruption within Halema‘uma‘u about a month later (the eruption that began on September 29, 2021). In May 2015, an intrusion here lasted less than a week and occurred during ongoing eruptions within Halema‘uma‘u and at Pu‘u‘ō‘ō. Intrusions also occurred here in the 1960s, 1970s, early 1980s, and in 2006, but only one of these events led directly to an eruption in that area. In December 1974, an intrusion began following this path southward, but then erupted as a series of short fissure segments with a total length of 5 km (3 miles) as it turned southwest. Of note is the fact that, before the 1974 eruption, earthquakes had migrated farther southwest than HVO has observed during recent unrest.

Information about the 2021 intrusion in this region.

Information about the 2015 intrusion in this region.

Information about the December 1974 eruption in this region.

WHAT WE ARE DOING

HVO continues to closely monitor Kīlauea volcano, watching for any signs of accelerated rates of earthquakes or ground deformation, or signs of shallowing earthquake locations, which usually precede a new outbreak of lava or propagating dike. We are also closely monitoring gas emissions and webcam imagery.

With permission from Hawai‘i Volcanoes National Park, HVO has installed two new webcams to monitor the region of unrest extending south-southwest of Kīlauea’s summit. These webcams can be accessed at the links below.

· S2cam

· MITDcam

All Kīlauea summit webcam views are available (here).

Note: All HVO webcams will be offline on Wednesday, October 25, from approximately 9:00 a.m. until 11:00 a.m. HST for system maintenance.

HVO will continue to post daily updates on our web site, along with photos, videos, and maps as they are available (here).

You can also receive daily Kīlauea updates via email by subscribing to the Volcano Notification System (here).

HVO is in frequent communication with Hawai‘i Volcanoes National Park and Hawai‘i County Civil Defense. Hawai‘i Volcanoes National Park has closed two trails in Kīlauea’s summit region given the unrest.

WHAT WE CAN EXPECT

Kīlauea volcano is not erupting. Unrest to the south-southwest of Kīlauea’s summit continues. It is unclear how long unrest will continue. It is not possible to say with certainty if current unrest will lead to an eruption. Although it is not possible to forecast an exact outcome, here are three possible scenarios that could play out in the coming days to weeks:

1. Magma continues to accumulate in the region south-southwest of Kīlauea’s summit, but eventually stops with no eruption.

2. Magma continues to accumulate in the region south-southwest of Kīlauea’s summit, with an eventual eruption inside the caldera, similar to recent eruptions at Halema‘uma‘u. In this scenario, we would expect to see accelerating rates of ground deformation and earthquakes beneath the caldera 1-2 hours before lava reaches the surface.

3. Magma continues to accumulate in the region south-southwest of Kīlauea’s summit, with an eventual eruption outside of the caldera, to the south or southwest. In this scenario, we would expect to see earthquake locations migrating away from the caldera, as they did prior to the December 1974 eruption, followed by accelerating rates of ground deformation and earthquakes 1-2 hours before lava reaches the surface.

No unusual activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone.