a reply to: Oneredbird
As you probably know, the area in and around Van Island gets plenty of smaller tremors, but bigger quakes are pretty rare. Within around 200 miles of
the approximate middle of the island (49.5 N, 125.5 W) there have been 25 quakes of mag 6.0 Mw**
or bigger since 1900, including 7 since 2000.
The largest of those (in this century) was a 6.7 Mw on Nov 2, 2004. It didn't cause much damage. The most powerful since 1/1/1900 was on June 23,
1946, when they had a mag 7.5 Mw.
But that's a fairly small area and there have been bigger quakes along or near the main west coast fault lines in the same period, including around
mag 8 just a few hundred km further north from Van Island. Down south from there, heading into Oregon and Cali, the quakes have tended to be
However, there has not been a megathrust quake along the Cascadia Subduction Zone (off the coast there) since Jan 26, 1700, when there was one around
a mag 9. Not possible to say when the next one may be. It's geologically "imminent", but that's from the perspective of long term averages. It could
be 100 years or more before it occurs. On the other hand, as the region is now within the broader average time interval for one, it could be today.
(Very low odds on that, though, thank goodness!)
So, does this mean your prediction is unlikely? Yes, but it's not beyond the realms of possibility and there is a small chance of such a quake in that
region, even in the next 3 days. However, a mag 6.4 Mw would only cause some local damage and hopefully not a lot of it. Whether it causes any serious
damage at all just depends exactly where it is. If it's at sea, like many of the prior ones have been, then it's not likely to produce major drama
unless it's a lot bigger than (say) a 6.4. The scale is logarithmic, so a 7.4, for example (with about ten times the shaking), would be far worse and
could have serious effects across a wider region.
"Mw" is the short form for "Moment magnitude", which is the scale seismologists have been using for larger quakes for the past few decades.
The mainstream media, being slow learners, still use "on the Richter scale", even though the larger quakes they mostly report about are not
measured by the USGS and others in Richter, but Moment Magnitude.