More than 40 earthquakes occurred in an area below Mauna Loa on Thursday, but the volcano is NOT erupting.
The Hawaiian Volcanic Observatory at the US Geological Survey reported that the small swarm of surface seismicity began at 1 a.m. HST on Thursday morning. It occurs below the upper seismic zone of Ka’ōiki, below the southeastern flank of Mauna Loa and northwest of Kīlauea Peak. Other Mauna Loa monitoring data streams remain stable and show no signs of increased activity.
REMARKS
On March 18, 2021, (HVO) recorded more than 40 earthquakes below the upper seismic zone of Ka’ōiki, about 13 miles WNW of Vulcan. These earthquakes occur in a group about a mile wide and 0.5-4 miles below the surface.
The biggest event in this sequence, starting late Thursday afternoon, was a magnitude 3.5 earthquake. Most of the events were smaller than magnitude 2 and were not widely reported by residents. Reported sensation events were described as weak shaking, with a maximum intensity of II on the modified Mercalli intensity scale.
The grouping of shallow earthquakes in this region does not mean that an eruption is imminent. HVO has experienced shallow earthquakes in this area for decades over several eruptive cycles in both Kīlauea and Mauna Loa. These earthquakes show no signs of magmatic involvement and are part of the normal readjustments of the volcano due to changing stresses inside it. Other monitoring data flows for Kīlauea and Mauna Loa, including soil deformation, gases and images, show no signs of increased activity.
HVO continues to closely monitor geological changes, seismicity, deformation and gas emissions at Kīlauea and Mauna Loa volcanoes. HVO will issue additional messages and changes to the alert level, as justified by the change of activity.
For more information about earthquakes in the Kaʻōiki Pali area, see the article Volcano Watch entitled “Why are swarms of earthquakes around Kaʻōiki Pali?” published by HVO scientists on March 1, 2012: https://www.usgs.gov/center-news/volcano-watch-why-do-swarms-earthquakes-occur-around-ka-iki-pali.
For information on recent earthquakes in Hawaii and eruption updates, visit the USGS Hawaiian Volcano Observatory website at https://www.usgs.gov/observatories/hawaiian-volcano-observatory.
Mauna Loa activity summaries are available by phone: (808) 967-8866. Other summaries of the Hawaiian volcano are also available by phone: (808) 967-8877.