Two earthquakes, one Thursday night and another Friday afternoon, rattled East Hawaii.
The Hawaiian Volcano Observatory recorded the first, a magnitude-4.6 temblor located beneath Kilauea Volcano’s south flank, at 11:20 p.m. Thursday.
The earthquake was centered about 4.3 miles south of Pu‘u ‘O‘o at a depth of approximately 4.2 miles.
Very light shaking was reported throughout the Big Island, Maui, and Lanai. The U.S. Geological Survey’s “Did you feel it?” service received more than 725 felt reports within the first hour after the earthquake.
According to HVO seismologist Ashton Flinders, the earthquake had no apparent effect on Kilauea or Mauna Loa volcanoes.
“Aftershocks are possible and may be felt,” Flinders said.
Kilauea’s south flank has been the site of 20 earthquakes of magnitude-4.0 or greater during the past 20 years. Most are caused by abrupt motion of the volcano’s south flank, which moves to the southeast over the oceanic crust.
This quake was likely an aftershock of the 2018 magnitude-6.9 earthquake as the volcano continues to settle.
The second quake in as many days was recorded by HVO at 2:19 p.m. Friday. It was a magnitude-4.3 earthquake also located beneath Kilauea’s south flank.
The temblor was centered about 3.5 miles south of Pu‘u ‘O‘o, about 1 mile north of Thursday night’s quake, at a depth of about 4.4 miles.
Weak shaking was reported around the Big Island. The “Did you feel it?” service received more than 220 felt reports within the first hour after the earthquake.
Flinders said the Friday quake had no apparent effect on Kilauea or Mauna Loa.
“It is not uncommon for aftershocks like these to happen in relatively short succession,” Flinders said. “Further aftershocks remain possible and may be felt.”
Aftershocks such as these quakes are the result of crustal settling from larger temblors, such as the M6.9 that occurred May 4, 2018. The location, depth and waveforms recorded as part of these two earthquakes are consistent with slip along this south flank fault.
HVO continues to monitor Kilauea and other Hawaiian volcanoes for any changes.
A map showing the locations of the earthquakes is posted on the HVO website at http://volcanoes.usgs.gov/hvo/earthquakes/. More details are available at the National Earthquake Information Center website at https://earthquake.usgs.gov/earthquakes/eventpage/hv72028657/.
Significant damage to buildings or structures because of these temblors was not expected.