The fault zone expected to generate the next big one lies underwater between 40 and 80 miles offshore of the Pacific Northwest coastline. Earthquake scientists have listening posts along the coast from Vancouver Island to Northern California. But those onshore seismometers have detected few signs of the grinding and slipping you would expect to see as one tectonic plate dives beneath another, with the exception of the junctions on the north and south ends of what is formally known as the Cascadia Subduction Zone. It is a puzzle, according to University of Oregon geophysics professor Doug Toomey. What is extraordinary is that all of Cascadia is quiet. Its extraordinarily quiet when you compare it to other subduction zones globally. The bottom line: Even with more sensitive instruments, its still eerily quiet out there. Which leads the researchers to conclude the dangerous Cascadia fault zone is stuck - or in science-speak, it is fully locked. ... The evidence pointing to the colliding tectonic plates being completely stuck has serious implications for earthquake risk on land in the Pacific Northwest. If there were low levels of offshore seismicity, then we could say some strain is being released by the smaller events, Toomey said. If it is completely locked, it means it is increasingly storing energy and that has to be released at some point.
Posted on: Thu, 04 Dec 2014 02:15:12 +0000
Trending Topics
Recently Viewed Topics
© 2015