LOL I was sitting here flying when that went off in April, 7.2 we also had a 6.9 a few months later. I believe.
It refers to Large 8.0 and over.
There are an average of ten 7.0 to 7.9 quakes per year since 1900. Last year 2010 there were double that.
Ah, then we're talking about a "big one". Last time I had a look, there is none in modern recorded history on the West Coast of that magnitude or greater for certain. Oddly though, and coincidently too since we're talking about the Juan de Fuca fault and not the San Andreas, it is believed the last "big one" that hit the US West Coast was some time "shortly" before the arival of the Lewis and Clark expedition at its final destination (I believe near the mouth of the Snake?). After L&C arrived at the ocean and settled down to get down to surveying buisness they quickly noted that none (zero, zip, nilch) of the native americans native to the Pacific would set up their villages and tribes on the coasts or anywhere near it, typicaly they would be well above the coast a couple miles or inland along the rivers, again by a couple miles at least. Upon inquiring, each tribe would tell them
the same thing, a couple I believe even had very old elders who recounted to L&C of their youth or first-hand accounts told to them - some recounting about the earth shaking violently for a long time, mountains and cliffs colapsing, rocks almost as big as a mountain rolling down the mountains and into the ocean, but primarily they all recounted the same major thing - loosing so many many of their loved ones and people of their tribe to "a great wave" that, according to the legends, came in from the sea (after the shaking to those who recounted it) over 150-feet high in some areas. Some tribes and nations, more dependent/focused on the ocean life than that of the forests to their backs, were completely wiped off the continent whole without a trace. The elders didn't claim to of lost hundreds, but thousands of tribesmen, which L&C didn't think was serious or possible (primarily that there was once so many indians, less-so about a monster wave but they didn't completely buy that either)... but given what we know now what Tsunamis are capable of today (and that they do exist and can happen), it is possible that mega coastal tribes of thousands of native americans once prospered along the West Coast and were simply wiped away along with all evidence of their existence in a split second. Lewis and clark in their diary noted these tales and also refered to some physical proof they observed in old downed and huge snapped trees all below a certain elevation along the coast that would seem to verify the magnitude of the Tsunami that struck. It was obvious though that enough time had passed that the forest had started recovering and was well re-establishing itself when L&C arrived, but L&C at the time concluded the locals were simply superstitious of the ocean.
Take that information from their expedition and diarys though into today and it is belived with some certainty the last major "big one" that hit the West Coast occured ~50-100 years before L&C arrived, somewhere offshore the Oregon coast, likely along the Juan de Fuca fault and over 8.0 magnitude, resulting a gigantic tsunami that hit vast regions of the west coast, displacing most the Native Americans that once lived there and forcing them to settle further inland where the threat of a deadly and sudden tsunami was avoided.
