Big Island ‘slow’ quake falls behind schedule
A delay in regular earth movements has scientists conjecturing
HILO » A "slow earthquake" predicted for Kilauea volcano by University of Hawaii geophysicists has failed to take place so far, but scientists are interpreting the no-show as additional information for understanding the mountain.
A slow quake is one in which the earth moves as much as in a typical major quake, but over the space of several days instead of seconds.
Only instruments can detect a slow quake.
Early in 2006, UH-Manoa earth scientists Ben Brooks, James Foster and others published a scientific paper that said slow quakes were found to have occurred in 1998, 2000, 2002 and 2005 on the western side of Kilauea.
The quakes were quite regular, happening on average every 774 days, give or take a week.
That meant there should have been another around March 17. The Hawaiian Volcano Observatory publicized the prediction on March 22, when time was already running out.
Scientists are still waiting.
"I think we're going to learn something out of the fact that it didn't happen," Foster said.
An early theory was that the violent Oct. 15 quakes on the other side of the Big Island might have upset the slow-quake schedule. That idea has pretty much been abandoned.
Foster's new, tentative theory is that the 774-day schedule was upset by earth changes associated with spreading of land just southwest of Kilauea's summit.
Starting last year, instruments showed a lot more magma rising from deep in the earth to within about two miles of the surface, said Volcano Observatory geophysicist Michael Poland.
Much of it remains below the surface, making the ground stretch, Poland said.
It is "difficult to tell" how that could affect the potential for slow earthquakes, which happen a couple of miles deeper, he said.
"There's so much that could be happening," he said.
Poland is confident that last month's slow quake was delayed but not canceled. "These slow earthquakes will continue every few years," he said.