Kīlauea summit rumbling; earthquake swarm observed Tuesday south of Halemaʻumaʻu crater

Kīlauea volcano on the Big Island is not erupting, but it is rumbling.

Kīlauea summit is exhibiting signs of elevated unrest. Beginning at 7:30 a.m. the morning of Aug. 15, a swarm of about 50 earthquakes that lasted several hours occurred at a depth of 1 to 2 miles throughout a 1.2-mile-long area directly south of Halemaʻumaʻu crater. The swarm was likely caused by magma movement in the volcano’s south caldera region and is a process observed consistently at the summit.

Summit tiltmeters showed no appreciable inflation associated with Tuesday’s earthquake swarm. Elevated seismicity decreased following the swarms and remains steady as of the morning of Aug. 16, but the activity is still elevated compared to last week.

During the past week, rates of seismicity increased, with 467 earthquakes of magnitude-3.2 and smaller occurring. A single magnitude-4.3 earthquake also occurred Aug. 13 in the region.

Summit tiltmeters have recorded net inflation across the summit with one brief episode of more rapid inflation on Aug. 13. No active lava has been observed since June 19 in the Halemaʻumaʻu crater.

Sulfur dioxide emissions from the summit remain low. The most recent SO2 emission rate, of about 86 tonnes per day, was measured Aug. 10. Measurements from continuous gas monitoring stations downwind of Puʻuʻōʻō in the volcano’s middle East Rift Zone remain below detection limits for SO2, indicating that SO2 emissions from Puʻuʻōʻō are negligible.

No unusual activity has been noted along Kilauea’s East Rift Zone or Southwest Rift zone. The volcano’s alert level remains at Advisory. Steady rates of ground deformation and seismicity continue along both.

The Hawaiian Volcano Observatory continues to closely monitor Kīlauea. The observatory is issuing daily Kīlauea updates and additional updates will be issued as needed.