USGS reports earthquake swarm and magma intrusion at Kīlauea summit in late September
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The U.S. Geological Survey reported that satellite imagery shows the extent of a near surface dike emplaced on September 30 to October 1, 2026, in Kaluapele, the summit caldera of Kīlauea volcano. The current Volcano Alert Level is WATCH and the Aviation Color Code is ORANGE.
An earthquake swarm began around 2 p.m. HST on September 30 about 1 mile beneath the vent complex in Halemaʻumaʻu. About 30 located events occurred in this area and by 8 p.m. HST the seismicity had moved northeastward at the same depth. An additional 50 events were located before 4 a.m. HST on October 1. The largest event was magnitude-3.5 at 7:55 a.m. HST on October 2. About 130 earthquakes were recorded in total.
The tilt at the Uēkahuna tiltmeter showed more than 40 microradians of change towards the northwest over about eighteen hours. The localized nature of the tilt changes indicated the intrusion was near the western rim of Kaluapele and much closer to the surface than the Halemaʻumaʻu magma chamber.
InSAR satellite images from September 24 and October 2 were used to construct an interferogram showing the interpreted location and length of the dike intrusion. The dike extends from the established vent area in Halemaʻumaʻu and cuts across the northwestern part of Kaluapele. The path follows fractures in the caldera floor that formed in 2018.
The dike path mapped within a thousand feet of the surface and magma is exploiting fractures formed during the 2018 collapse. Six vents opened on and below the northwest wall of Halemaʻumaʻu on September 14-16.
The USGS said the impact of increased pressurization and earthquakes on the next episode of lava fountaining, if any, is unknown. It is not possible to forecast an exact outcome of this activity.
