Saturday’s 4.3 Mauna Loa Earthquake has no Apparent Effect on Volcano

The US Geological Survey’s Hawaiian Volcano Observatory recorded a magnitude-4.3 earthquake located beneath Mauna Loa’s south flank on Saturday, April 3, at 11:15 a.m., HST. This earthquake was preceded by a magnitude-3.9 at approximately the same location on 11:02 a.m., HST. 

The magnitude-4.3 earthquake epicenter was 3 miles NW of Pāhala, near Wood Valley, with a depth of approximately 5 miles below sea level.

The USGS “Did you feel it?” service received more than 130 felt reports within the first hour of the earthquake, including one report from Kaua‘i. 

According to HVO Scientist-in-Charge Ken Hon, the earthquake had no apparent effect on Mauna Loa or Kīlauea volcanoes. “At this time, we have not observed any changes in activity at Mauna Loa or Kīlauea as a result of this earthquake. Please be aware that aftershocks are possible and may be felt. HVO continues to monitor Kīlauea and other Hawaiian volcanoes for any changes.”  

The HVO reports that both the magnitude-4.3 and magnitude-3.9 earthquakes on Saturday “appear to be slip along vertical faults caused by southeast motion of Mauna Loa’s south flank.” Saturday’s earthquakes are significantly shallower and west of the location of the ongoing seismic swarm under the Pāhala area that began in August 2019, according to the HVO. 

“This does not represent a significant departure from the seismic activity observed over the past year and the Volcano Alert Level for Mauna Loa remains at ADVISORY. Other Mauna Loa monitoring data streams show no significant change in deformation rates or patterns that would indicate increased volcanic hazard at this time,” the HVO reports.  

The Alert Levels / Color Codes remain at WATCH/ORANGE for Kilauea and at ADVISORY/YELLOW for Mauna Loa at this time.