The Oregon Department of Geology and Mineral Industries recently found and mapped a new fault on Mount Hood that in the past has delivered quakes in the 6 to 7 range. The fault is determined to be active and adds to the complexity of the fault system in the northwest US and southern BC. This fault is close to the hood river and so parallels the coast heading north from the mountain. But being only 70 km from Portland and if the whole fault ruptured at once the effects would be felt there and all the places between. Just another thing for the west coast to be aware of and to plan for.
This area is riddled with faults, some big some small. This one seems larger than the most but is small compared to cascadia. If and when Cascadia does go off a lot of these parallel faults will also be triggered either then or as after shocks as the plate subsides and stresses are moved around until the zone gets back into a steady state. It’s also these smaller quakes that take up strain and allow the stress on the main cascadia fault to build to a fully loaded at all parts zone before it lets go. Without these smaller parallel faults the stress would build unequally and the cascadia fault would rupture as bits an pieces instead of the all at once mega quake we are expecting.
- Hidden Mt. Hood fault discovered (seattletimes.nwsource.com)