Skip to comments.Vanity: Question about Seismic activity
Posted on 10/01/2007 5:22:14 PM PDT by Blogger
Posted this question on another thread but had very little response. As I look at the ring of fire right now, there is a massive amount of activity, BIG activity in the Pacific ocean towards Asia. There is also a lot of activity in South America and a little in Central America. The only thing on my chart on the west coast that registered at 4.0 or above was a small quake in Oregon.
Question is, with all of these plates shifting, and the plates around our nation's plates staying pretty quiet, what is this doing to our risks of a massive release? The answer I received was that maybe a lot of these smaller ones are enough to relieve the pressure build up. Any seismologists or other earthquake experts out there?
No one knows. There is not enough historical data to empirically answer your query
My understanding is there is always “massive” activity on the ring of fire, that just goes with the subduction. The plates that form the two sides of the San Andreas fault are moving lateral to each other, not one under the other like most of the ring of fire. The San Andreas blows off a big quake every 150 years or so. The last big one along the SA fault in Northern California was the 06 San Francisco quake, and in Southern California it was the 1857 Fort Tejon quake.
California is due for a big one on the SA, regardless of what is going on around the Pacific.
Maybe the Three Gorges Dam is at fault. ;-D
I would not want to be in Memphis if the New Madrid fault has a happy day
I’m not an expert but I’ve been watching quakes online for about 8 years. It usually is more active on the eastern side of the Pacific. I don’t know why. Just something I’ve observed over the years. However, looking at that map, it does seem unusually quiet over here on the Western-Hesmisphere-side of the ring of fire. Especially Alaska. I don’t know what that means, either. Hope I helped. :)
“I would not want to be in Memphis if the New Madrid fault has a happy day”
I’m not sure I’d want to be ANYWHERE in Southwest Missouri if New Madrid cuts loose, much less Memphis.
Firstly, I am not a seismologist. However, I do have an opinion.
I think there is very little correlation to what is happening on the other side of the world. The scale is too immense.
The theory of stress release does work on a local level though.
It seems that the scale(richter) scale of these earthquakes is huge. Quite a few 7s or higher. Seems unusual, but I could be wrong.
Very interesting about 1857 Fort Tejon quake.
New Madrid is interesting. I’ve been watching that one a while and it is pretty quiet for something that blew so big in 1811.
Of course, there is the seismicity of Yosemite as well. But these are things that we don’t think of so much when we think American earthquakes. We tend to think West Coast. And it has been oddly quiet.
I’m about 70 miles NW of New Madrid. All of my immediate family lives somewhere along the New Madrid fault.
Once you start looking at that stuff daily for years you realize it pretty much always looks like that.
I've noticed when people START looking at global seismic maps they really astonished at the level of activity. Also there's greater news coverage of worldwide quakes.
Not nearly as much as people think. Each whole number of magnitude is about 32 times more energy release.
The overwhelming majority of worldwide seismic stress is released in massive earthquakes. All the little quakes DON'T really add up.
For example, in Southern California it would take over 30,000 magnitude 4 quakes to release the same stress as a damaging magnitude 7 quake. So while people may comfort themselves when a 4.0 occurs there that "at least it's releasing stress" really it's irrelevant.
even the 7 & 8 pointers?
There have been 12 Mag 7+ quakes worldwide this year; in an average year, there are 18 such quakes. So, actually, we're a hair BELOW average in the number of such quakes.
However, there is on average 1 Mag 8+ quake a year, and we've had 3 already, so that number is above average. It's not a record for the number of such quakes.
There was an interesting article in a scientific journal a few years ago that showed some tentative evidence that there were decadal-scale cycles in subduction quakes vs. large strike-slip quakes (like the San Andreas)- almost all the 8+ quakes are subduction ones so you'd ger more of the REALLY big quakes in the subduction cycles, which we'd appear to be in now, if such a thing does exist.
There's certainly been no statistically glaring increase in large quakes, though.
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