New Research, Maps Highlight Need For Earthquake And Tsunami Prep
The earthquake and tsunami threat to the Northwest from the offshore Cascadia fault was in the news in multiple ways Thursday. Canadian researchers have reconstructed a prehistoric record of great earthquakes on that shared fault. It reconfirms that we're due for another Big One.
Coincidentally in Oregon, tsunami preparedness is getting a renewed look.
A team of researchers on Vancouver Island analyzed a sediment core taken from Effingham Inlet in Barkley Sound. They found evidence of 22 major earthquakes over the past 11,000 years -- an average of one about every 500 years. But radiocarbon dating shows the interval can be as little as 200 years or longer than 900.
That means the next Big One could strike any day now -- the last Cascadia megaquake happened in January 1700.
The chronology described in the new research paper correlates closely with the results of prior digs in coastal salt marshes in Oregon and Washington State and sampling in undersea canyons and two lakes.
"It's becoming more and more clear that big subduction earthquakes are reliably recorded in many environments, something that will eventually allow us to combine all these data and estimate slip models and magnitudes for past earthquakes," said Oregon State University Prof. Chris Goldfinger. "At least that's where I think the science is headed." Goldfinger's previous sleuthing on the Cascadia fault was cited by the Canadian team.
This latest research was published online in the Canadian Journal of Earth Sciences on the same day that Oregon legislators in Salem listened to ideas for how to better prepare for tsunamis. Emergency planner Jay Wilson says a top recommendation in the new Oregon Resilience Plan is to relocate coastal schools, hospitals, and fire stations to higher ground.
"We know you can't move all these homes off the beach and people don't want to live that far away. But if there is key infrastructure for there that they are going to have to rely on, relocation needs to be the first discussion point."
This comes just as the state of Oregon has completed a four-year process of remapping the tsunami hazard zone on its coast. In most places, the new maps show more streets and buildings at risk than previously thought.
On the Web:
Study: Northwest paleoseismic event chronology - Canadian Journal of Earth Sciences
Oregon Tsunami Clearinghouse - DOGAMI
Oregon Resilience Plan - Oregon Office of Emergency Management
Resilient Washington State - Washington DNR