A group of researchers have calculated the possibility of a megaquake such as Japan’s 9.0 quake and tsunami in 2011 happening on America’s West Coast. A study published in the October issue of Bulletin of the Seismological Society of America details how researchers used computer models of future seismic activity and analysis of past activity dating back thousands of years to find out how often the Pacific’s earthquake zones produced 9.0-magnitude quakes. According to the study, these zones produce earthquakes with magnitudes of at least 9.0 every 10,000 years on average.
According to NBC News, seismologists were surprised by the 9.3-magnitude quake and tsunami that hit Sumatra in 2004 as well as the megaquake and tsunami that devastated Japan in 2011. Previously, they reportedly didn’t know that subduction zones, where one geological plate is diving beneath another, were capable of producing quakes as strong as these.
Yufang Rong, a seismologist at FM Global's Center for Property Risk Solutions, was part of a team that ran computerized Monte Carlo simulations on seismic data from various subduction zones around the Pacific. They found that besides the 10,000-year average for 9.0 quakes, earthquakes of magnitude at least 8.5 should be expected every 250 years, while those 8.8 can be expected every 500 years.
However, Rong cautioned that the figures were based on statistical distribution, meaning the time frames are not rigid. “We are talking about probabilities,” said Rong.
Chris Goldfinger, a marine geologist and professor at Oregon State University, noted that the Cascadia Subduction Zone, which runs from Vancouver Island down to northern California, is overdue for a megaquake. “We’re 300 years into a 240-year cycle,” said Goldfinger.
“The most important thing is to strengthen or replace infrastructure to make sure that our lifeline systems like power and water will not be so severely damaged that they require years to repair,” said Ian Madin, a geologist and chief scientist at Oregon Department of Geology and Mineral Industries.