By Brooks Baehr - bio | email
MANOA (HawaiiNewsNow) - The earthquake that triggered the deadly tsunami off Japan earlier this month surprised scientists who did not expect such a powerful quake at that location.
Now Greg Moore, Chair of the Department of Geology and Geophysics at the University of Hawaii, and Rhett Butler, a geophysicist and seismologist who works with Moore at U.H., are now rethinking the source of the tragedy wondering how the next event might impact Hawaii.
"The surprise as a seismologist is knowing the earthquake record in this area where there had been nine major damaging earthquakes in the last 100 years, many of them creating tsunamis, large amount of strain release going on, magnitude in the mid 7's to the mid 8's ... that you could build up enough strain energy to now have a magnitude 9 earthquake," Butler said.
As tectonic plates collide off the coast of Northern Honshu, pressure builds. Scientists theorized the magnitude six, seven, and eight earthquakes there over the past 100 plus years were relieving sufficient pressure to prevent a magnitude nine earthquake from developing. Now they realize that was not the case.
"Apparently when stress builds up and drops, it doesn't go to zero," Moore said while referencing a graphic to illustrate his point. "Finally it (the stress) builds up until you have an enormous amount of energy still left, and a huge earthquake," he added.
What might this mean for Hawaii? Moore and Butler agree it means tsunami sources, including the Aleutian Islands, where magnitude 7's and 8's occur on a somewhat regular basis may be building toward a catastrophic magnitude nine earthquake.
"If you are just getting 8.5's up on the Aleutian arch, could you get a nine up there?" Butler asked.
"If there were a magnitude 9 earthquake up in the Aleutians … it would send a fairly large tsunami down to Hawaii," Moore said.
A comparatively small 7.8 magnitude quake in the Aleutians generated a tsunami that killed 96 people in Hawaii in 1946. And in 1957 an Aleutian quake with an 8.3 magnitude produced 50 foot high run-up on Kauai.
"And so, you have to be concerned that potentially a magnitude nine along the Aleutian arch is potentially damaging and is that something we need to really look at," Butler added.
Thursday on Hawaii News Now at 6 p.m. Moore and Butler answer questions about earthquake clusters. There have been so many big quakes around the Pacific in recent years, are we destined to have another soon?