Over 200 Earthquakes Shook World's Largest Volcano in Hawaii: Is Eruption Imminent?

Geologists wonder if the more than 200 earthquakes that have shaken Hawaii over the past seven days will cause an eruption at Mauna Loa, the most active volcano in the world, or whether the eruption will cause a powerful earthquake.

Monitoring the Situation

There are currently no signals of an impending eruption, and Mauna Loa is not currently erupting. However, as evidenced by increased seismic activity and summit inflation, Mauna Loa is still experiencing high levels of instability. Scientists from the USGS' Hawaiian Volcano Observatory (HVO) believe that the resumed magma intake of 2-5 miles under the top of Mauna Loa is what is causing the present instability.

HVO recorded 35 small-magnitude (below magnitude 3) earthquakes during the previous 24 hours, located 2-3 miles under the Mokuweoweo caldera and 4-5 miles beneath the northwest face of Mauna Loa at a higher height. Historically, these two areas have seen earthquake activity when there has been instability on Mauna Loa.

Meanwhile, aftershocks from a devastating earthquake in the region on Friday are still being felt close to the hamlet of Pahala on Mauna Loa's southeast slopes. According to USGS, the Pahala area has had more than 150 aftershocks in the last 48 hours. Twenty of these seismic occurrences had a magnitude more than 2.5, while 4 had a magnitude greater than 3.

Also Read: Mauna Loa, Hawaii's Biggest Volcano, is Currently in an Active Phase

Public Risk

The Mauna Loa volcano's summit was closed to the public on October 6 due to an overall uptick in seismic activity in previous weeks. Since June 2022, the number of earthquakes has increased from 5 to 10 per day to 10 to 20 per day in July and August and then to 40 to 50 per day during the first two weeks of the month. On September 23 and 29, there were daily peaks of around 100 earthquakes.

The National Park Service said in a news statement announcing the closure of the summit area, "Due to high seismic activity on Mauna Loa and as a precautionary measure, Hawai'i Volcanoes National Park is closing the Mauna Loa summit backcountry until further notice." The public may still access Mauna Loa Road and the lookout at 6,662 feet in height.

Researchers are attempting to predict what will occur next.

Jefferson Chang, a geophysicist at HVO, stated, "Whether these huge, shallow earthquakes under volcanoes lead to eruptions, or if it is the magma moving stresses along faults that generate earthquakes, is a bit of a chicken or egg dilemma. These are two end-member possibilities, and both are most likely correct. Volcanic eruptions and earthquakes frequently occur in tandem."

Continued Research

HVO researchers examine various monitoring streams to track changes in Mauna Loa's behavior. These changes may let scientists know when an eruption is more likely. One of the signs that raise the likelihood of a Mauna Loa eruption from "not necessarily" to "very likely" is the occurrence of large shallow earthquakes. For instance, the 1984 eruption of Mauna Loa was preceded by an earthquake with a magnitude of 6.7. Only two days before the eruption began in 1950, a significant earthquake also preceded the eruption. On the other hand, a large earthquake, such as the 7.7 magnitude one that occurred in Kalapana in 1975, had little effect on the island's eruption activity.

Large shallow earthquakes "may constitute a tragedy on their own, not only a potential prelude to volcanic eruptions," according to Chang. "Large earthquake damage can lower the dangers and risks by strong shaking.