‘The longest record for a subduction zone is from Cascadia, where scientists have linked buried marshes and submarine landslides with a series of about 22 megaquake quakes going back 10,000 years. The time between quakes ranges from 200 to 1,000 years, with an average of about 500 years’
Related On This Site: The last big Cascadia subduction zone earthquake likely occurred on Jan 27th, 1700, at magnitude 9.0. The article suggests an occurence anywhere from 300-350 year intervals up to 400-600 year average intervals (new research suggests the former). It’s just over 311 years and counting.
Apparently, it happen at 5:25 am PST, and I had no idea. About 1 in 4 or 5 people I spoke with today either felt it, or were woken up enough to realize something had happened, but weren’t quite sure what.
Here’s a good map at the USGS site which measures how many people responded and intensity.
The vibrations and earth movement could be felt for only a few seconds, though it happened along the Nisqually fault, where the February 21, 2001 6.8 earthquake occured.