CORVALLIS, Ore., June 11 (UPI) -- An undersea volcano located about 250 miles off the Oregon coast produced clear seismic signals hours before an eruption, researchers say.
Last year, researchers at Oregon State University correctly forecast the eruption of Axial Seamount in advance.
Documentation of inflation of the undersea volcano from gradual magma intrusion over a period of years led to the eruption forecast, but new analyses of data from underwater hydrophones also show an abrupt spike in seismic energy about 2.6 hours before the eruption started, an Oregon State said in a release Sunday.
The researchers say such a finding could lead to short-term forecasting of undersea volcanoes in the future.
The link between seismicity, seafloor deformation and the intrusion of magma can provide new insights into eruption patterns, they said.
"Axial Seamount is unique in that it is one of the few places in the world where a long-term monitoring record exists at an undersea volcano -- and we can now make sense of its patterns," researcher Bill Chadwick said.
"We've been studying the site for years and the uplift of the seafloor has been gradual and steady beginning in about 2000, two years after it last erupted.
"But the rate of inflation from magma went from gradual to rapid about 4-5 months before the  eruption. It expanded at roughly triple the rate, giving a clue that the next eruption was coming."
Meanwhile, hydrophones on Axial monitoring sound waves for seismic activity recorded a burst of small earthquakes just hours before the eruption.
"Now that we know some of the long-term and short-term signals that precede eruptions at Axial, we can monitor the seamount for accelerated seismicity and inflation," researcher Bob Dziak said, noting the researchers hope next time to "catch the volcano in the act."