Questions about earthquakes off the Oregon coast – please read on…?
I live in Washington state, and receive notifications from the USGS about earthquakes in the Pacific Northwest area. There have been a series of quakes off the Oregon coast over the past 10 days or so – the largest was a 5.2. I’m not a geologist by any stretch of the imagination, but I was watching the news last night, and a short piece on the quakes mentioned that this kind of series of quakes is usually associated with volcanic eruptions. Of course, right now, there IS no volcano in that region; is it possible that we’re about to see a new one begin? I’d be curious to know what people educated in this sort of science think – thanks!
Btw – I’m not "worried" about it or anything; I’m just wondering if it’s POSSIBLE. I certainly think it would be fascinating to see if it occurs, but I have no idea if that’s possible. I do remember MANY years ago (I’m 53) the process of a volcano (in the Atlantic, I think) turning into an island; it was documented in something like Life or National Geographic, but I was much too young at the time to do much more than look at the pictures.
http://earthquake.usgs.gov/eqcenter/recenteqsww/Maps/10/230_45.php
Ok – yeah, I know about the Cascade volcanoes, of course (I can look out my window and see Rainier, after all…). I guess it’s just that the USGS folks are saying there’s no volcano in the immediate area of the quakes, so I’m wondering if it’s reasonable at all to think that another one MIGHT form. Of course, I know it would take an EXTREMELY long time to form to the size of a Rainier or a St. Helens, but *could* this be the start of a new one?
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3 comments
idiot detector on October 24, 2009 at 7:00 pm
There is always that possibility.
However, this area is different from the area you referenced where an island built in the Atlantic — that was the island of Surtsey off the coast of Iceland that began erupting in 1963 — which is on the mid-ocean ridge. Obviously, this is not a mid-ocean ridge.
Since the coast of Oregon is on a strike slip fault (basically a continuation of the San Andreas), it is not as likely to have associated volcanoes as it would if it were a major subduction zone like Indonesia or Japan.
However, there is a subduction aspect to this fault line as it turns from a true strike-slip motion to more of a subduction as the Juan de Fuca Plate is being subducted beneath the North American Plate. Basically the Juan de Fuca plate is being crushed between the Pacific and North American Plates, so the earthquakes could also be the result of this crushing instead of the more typical subduction-type earthquakes.
Where there is subduction, there is an opportunity for volcanoes.
The "Cascadia Subduction Zone", a 1000 km long thrust fault which is the convergent boundary between the Juan de Fuca and North American plates and is the most extensive fault in the Pacific Northwest area. It surfaces about 50 miles offshore along the coasts of British Columbia, Washington, Oregon and northern California. No historic earthquakes have been directly recorded from this source zone. According to recent research, an earthquake estimated to be as large as 8.0 to 9.0 occurred in this zone in January of 1700.
Yankie K on October 24, 2009 at 7:00 pm
Your living next a subduction zone where the pacific ocean is sliding under North America, the earth quakes you are experiencing form the ocean are probably linked to movement in this subduction.
Harmonic earthquakes are know to precede a volcanic eruption but these would be very shallow and I would imagine be inland to the east.
Rossghjr on October 24, 2009 at 7:00 pm
Your statement that there is no Volcano in the region is false, all of the major mountains in the Cascade range are volcanic in nature, Mount Saint Helens, Mount Hood, Mount Rainer, Crater Lake, Shasta Etc…. These mountains/volcanos are typically inactive for long periods of time with breif periods of very violent activity…