Magnitude 5.7 earthquake strikes Mauna Loa volcano on Hawaii’s Big Island; no tsunami expected

Hawaii's Mauna Loa volcano, in the background, towers over the summit crater of Kilauea volcano in Hawaii Volcanoes National Park on the Big Island. Photo / AP

A magnitude 5.7 earthquake struck the world’s largest active volcano on Friday — Mauna Loa on the Big Island of Hawaii — knocking items off shelves and cutting power in a nearby town but not immediately prompting reports of serious damage.

The earthquake, which didn’t cause a tsunami and which the US Geological Survey initially reported as magnitude 6.3, was centred on Mauna Loa’s southern flank at a depth of 37km, 12km southwest of Pahala.

“It shook us bad to where it wobbled some knees a little bit,” said Derek Nelson, the manager of the Kona Canoe Club restaurant in the oceanside community of Kona on the island’s western side. “It shook all the windows in the village.”

There was a power outage affecting about 300 customers in Naalehu that appeared to be related to the earthquake, said Darren Pai, spokesman for Hawaiian Electric Company.

The earthquake struck after 10am local time, less than two hours before an unrelated quake with a preliminary magnitude of 4.6 shook Southern California.

Mauna Loa last erupted in late 2022. It’s one of five volcanoes that make up the Big Island, which is the southernmost in the Hawaiian archipelago.

Earthquakes can occur in Hawaii for a variety of reasons, including magma moving under the surface. In today’s case, scientists believe the likely cause was the weight of the Hawaiian Islands bending and stressing the Earth’s crust and upper mantle.

That’s what caused a magnitude 6.9 earthquake that struck off Kiholo Bay on the Big Island’s northwest coast in 2006. That temblor damaged roads and buildings and knocked out power as far away as Honolulu, on the island of Oahu about 322km to the north.

The observatory said today’s earthquake didn’t affect either Mauna Loa or a neighbouring volcano, Kilauea.

Jessica Ferracane, a Hawaii Volcanoes National Park spokeswoman, said there was no apparent damage to its roads or visitor centres. Earthquakes are not uncommon, she said, but this one was “much more intense” than usual.

The Hawaiian Islands have been built by successive volcanic eruptions over millions of years. The vast majority of earthquakes in Hawaii occur on and around the Big Island. About once every 1.5 years, there is an earthquake in the state that is magnitude 5 or greater, according to the Hawaiian Volcano Observatory.

The Big Island is mostly rural and hosts cattle ranches, coffee farms and resort hotels. But it also has a few small cities, including the county seat of Hilo, population 45,000.

Today’s earthquake could be felt in Honolulu. Big Island Mayor Mitch Roth was at a cardiologist appointment there and initially thought he was experiencing side effects from a procedure: “All of a sudden I felt like I was getting dizzy.”

He said he immediately got on the phone with his emergency management officials when he realised it was an earthquake, and that he was heading to the Honolulu airport to try to get an earlier flight back.

Grace Tabios, owner of Will and Grace Filipino Variety Store in Naalehu, said the shaking knocked down her husband, who was working at their coffee farm in Pahala. At the store, jars of mayonnaise and medicine from the Philippines fell off the shelves.

“Some things fell down but didn’t break,” Tabios said.