Two earthquakes that rattled the island of Hawai'i on Friday could be tied to the Mauna Loa volcano at Hawai'i Volcanoes National Park/NPS, Janice Wei file

Two moderate earthquakes, one of which registered as a magnitude 5 temblor, rattled the island of Hawaii on Friday morning and could be related to recent geologic activity at Mauna Loa in Hawai'i Volcanoes National Park, the U.S. Geological Survey reported.

"The first earthquake (magnitude-4.6) was slightly offshore and south of Pāhala, at about 13 kilometers (8 miles) depth. It was followed 24 seconds later by a larger magnitude-5.0 earthquake just south of Pāhala, 7.4 kilometers (4.6 miles) beneath Highway 11," the USGS's Hawaiian Volcano Observatory said. "These two larger earthquakes were followed by a string of aftershocks, mostly less than magnitude-3.0, but including some larger ones up to magnitude-4.0. ... The aftershocks could continue for several days to possibly weeks and may be large enough to be felt."

Last week the observatory reported an uptick in earthquakes beneath the iconic volcano in July and August, when the daily number of temblors doubled from 5-10 a day to 10-20. More recently, 40-50 quakes a day have been recorded over the past two weeks, the observatory reported. On September 23rd and 29th, there were more than 100 earthquakes a day, it added.

The two quakes Friday morning were reported by more than 600 people from the Island of Hawaiʻi and felt to a lesser extent across the entire state, the observatory said. "Shaking from the larger earthquakes may have been strong enough to do minor local damage, especially to older buildings. The two earthquakes occurred within 24 seconds of each other creating shaking of longer duration and possibly greater intensity than either of the earthquakes would have created on their own," it added.

"This sequence of earthquakes appears to be related to readjustments along the southeast flank of Mauna Loa volcano," the geologists noted. "There has been no immediate effect on the continuing unrest beneath Mauna Loa summit, which remains elevated at levels similar to the past week. On several occasions large earthquakes have preceded past eruptions of Mauna Loa, though these have typically been larger than today’s earthquakes. It is not known at this time if this sequence of earthquakes is directly related to the ongoing unrest on Mauna Loa."

Rising to more than 2.5 miles (4 kilometers) above sea level, Mauna Loa, a shield volcano, is the largest active volcano on Earth. According to the USGS, the Hawaiian name "Mauna Loa" means "Long Mountain." It is among Earth's most active volcanoes, having erupted 33 times since its first well-documented historical eruption in 1843, the agency adds. "It has produced large, voluminous flows of basalt that have reached the ocean eight times since 1868. It last erupted in 1984, when a lava flow came within 4.5 miles (7.2 kilometers) of Hilo, the largest population center on the island."

Kīlauea, Mauna Loa's sister volcano in Hawai'i Volcanoes National Park, erupted for months in 2018, with the national park suffering significant damage, as did surrounding communities. Those eruptions covered nearly 13 square miles of the island with lava flows, which also forced thousands to evacuate their homes; more than 700 homes were destroyed by the eruptions. Damage estimates ran to at least $100 million, with the park's Crater Rim Drive significantly cracked and buckled while the park's Jagger Museum sustained significant structural damage from thousands of related earthquakes.

A summit eruption that began within Kīlauea's Halema‘uma‘u crater on September 29, 2021, is ongoing, the USGS notes.