A team of scientists from the University of Hawaii at Mānoa (UHM) has determined that the probability of a magnitude 9+ earthquake hitting the Aleutian Islands is approximately nine percent in the next 50 years. An earthquake of this magnitude would have enough power to create a mega-tsunami that could threaten the inhabitants of Hawaii, and reports estimate that damage from such an event would cost nearly $40 billion.
Earthquakes occur when two sections of the earth's crust - made up of rocky plates - slip past one another. The location of this event is called the fault, and a subduction zone is the region where numerous faults occur. Due to the nature of the Aleutian Islands' subduction zone, Hawaii is particularly vulnerable to a tsunami caused by an earthquake in this region.
"Necessity is the mother of invention," said Rhett Butler, a geophysicist at the UHM School of Ocean and Earth Science and Technology (SOEST) and lead author of the study. "Having no recorded history of mega tsunamis in Hawaii, and given the tsunami threat to Hawaii, we devised a model for magnitude 9 earthquake rates following upon the insightful work of David Burbidge and others."
During the course of their research, Butler and his team created a numerical model founded solely upon the basics of plate tectonics: fault length and plate convergence rate. In order to ensure that uncertainties in the data were properly accounted for, they took advantage of Bayesian techniques.
The team validated their model using the recorded histories and seismic/tsunami date connected to the five earthquakes greater than magnitude 9 since the year 1900, which took place in Tohoku, Sumatra-Andaman, Alaska, Chile and Kamchatka.
"These five events represent half of the seismic energy that has been released globally since 1900," Butler said. "The events differed in details, but all of them generated great tsunamis that caused enormous destruction."
The team also took into account tsunamis that occurred prior to recorded history by examining evidence harbored in geological layers in coastal sediments, volcanic tephras and archaeological sites.
"We were surprised and pleased to see how well the model actually fit the paleotsunami data," Butler said.
The results revealed that the chance of a magnitude 9 earthquake in the greater Aleutians over the next 50 years is nine percent, with the margin of error being three percent. Using this data, the team estimates that the cost of such a risk is $3.6 billion, which equates to $72 million per year.
The findings were published in the April 20 issue of the Journal of Geophysical Research.
