More than 40 earthquakes occurred in an area below Mauna Loa on Thursday, but the volcano did NOT erupt.
The U.S. Geological Survey’s Hawaiian Volcano Observatory reported that the small swarm of shallow seismicity began at 1 a.m. Thursday morning. It occurs below the upper seismic zone of Ka’ōiki, below the southeastern flank of Mauna Loa and northwest of the summit of Kīlauea. Other Mauna Loa monitor streams remain stable and show no signs of increased activity.
OBSERVATIONS
On March 18, 2021, (HVO) recorded more than 40 earthquakes below the upper seismic zone of Ka’ōiki, approximately 13 km WNW of the volcano. These earthquakes occur in a group about one kilometer wide and 0.5 to 4 kilometers below the surface.
The biggest event in the series, such as late Thursday afternoon, was an earthquake with a magnitude of 3.5. The majority of the events were less than 2 and were not widely reported by residents. Reported sensory events were described as weak tremor, with a maximum intensity of II on the Modified Mercalli intensity scale.
Grouping of shallow earthquakes in this region does not mean that an eruption is imminent. HVO has recorded shallow earthquakes in this area for many decades during different eruption cycles at both Kīlauea and Mauna Loa. These earthquakes show no signs of magmatic involvement and are part of normal volcanic readjustments due to changing stresses in them. Other monitoring data streams for Kīlauea and Mauna Loa, including landslides, gas and images, show no signs of increasing activity.
HVO is closely monitoring the geological changes, seismic, deformation and gas releases at the Kīlauea and Mauna Loa volcanoes. HVO will issue additional messages and alert level changes as justified by changing activity.
For more information on earthquakes in the Kaʻōiki Pali area, see the Volcano Watch article entitled, “Why Do Swarms of Earthquakes Occur Around the Ka’ōiki 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.
Visit the USGS Hawaiian Volcano Observatory website at https://www.usgs.gov/observatories/hawaiian-volcano-observatory for information on recent earthquakes in Hawaii and eruption updates.
Mauna Loa activity summaries are available telephonically: (808) 967-8866. Other Hawaii volcano summaries are also available by phone: (808) 967-8877.