Shallow earthquakes at Mauna Loa elevate alert level

Mauna Loa (Photo: USGS/Hawaiian Volcano Observatory)

Due to shallow earthquakes occurring in locations similar to those that preceded Mauna Loa’s two most recent eruptions in 1975 and 1984, the current volcano alert level has been raised to advisory from normal.

This increase in alert level does not mean that an eruption is imminent or that progression to an eruption is certain.

Geologists say the advisory has nothing to do with Wednesday’s earthquake in Chile, or the resulting tsunami advisory, and the timing is coincidental.

The advisory is the result of increased activity within the volcano that scientists have been monitoring for months.

The Hawaiian Volcano Observatory’s seismic stations continue to record elevated rates of shallow, small-magnitude earthquakes beneath Mauna Loa’s summit, upper Southwest Rift Zone, and west flank.

For at least the past year, the rate of shallow earthquakes has varied but overall has remained above the long-term average.

During this same time period, HVO has measured ground deformation consistent with recharge of the volcano’s shallow magma storage system. Together, these observations indicate the volcano is no longer at a background level of activity.

“We have that increased magma supply, or at least we can measure it where magma is accumulating within the volcano, and concurrent with that, we have a slight increase in seismicity, so both of those indicators together are consistent with Mauna Loa is not a dead volcano and that it’s showing albeit small signs of reawakening,” explained Frank Trusdell, geologist, USGS Hawaiian Volcano Observatory.

The current rate and pattern of ground deformation is similar to that measured during inflation of Mauna Loa in 2005, an episode of unrest that did not end in an eruption.

It is possible that, as in 2005, the present heightened activity will continue for many months, or even years, without progressing to an eruption. It is also possible that the current unrest is a precursor to an eruption, as was the case prior to eruptions in 1975 and 1984. At this early stage of unrest, it cannot be determined which of these possibilities is more likely.

HVO continues to monitor the volcano closely and will report any significant changes.

Stay informed about Mauna Loa by following volcano updates and tracking current monitoring data on the HVO web page.

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