reply to post by kdog1982
Oh, it's you!
Oh, I'm sorry, man... I remember avatars better than names. I loved that avatar. Casual dog, leaning there, looking cool.
Now I'll have to learn your new one.
Okay on topic: as you know Calif quake frequency varies around a bit, so yep, sometimes there are quiet days and weeks then it gets busy again. I
remember a while back when their weekly map showed 800-plus quakes.
But about the little quakes relieving pressure... That's a yes and no, I think. True, they might a bit, specially in that region, but the big mag
quakes are so many times larger in terms of energy release that it's hard to know if the small ones made a lot of difference.
Like, the southern section of the SAF is believed capable of producing a mag 8.1 or thereabouts, based on new assessments of possible rupture length
and so on. So, okay, there are heaps of little mag 1-range quakes, lots of mag 2s and all, and the odd mag 3 or bigger, but when we consider that a
mag 8.1 is 1,000,000 times bigger than a mag 2.1 in terms of shaking and it releases 1,000,000,000 times more energy, we'd need one heck of a lot of
mag 2.1s (for example) in the right places along the right fault to relieve that much stress.
Even with a mag 8.1 versus a mag 4.1, the mag 8.1 is 10,000 times bigger and releases a million times more energy. (It's the total energy release that
matters, as you'd certainly know.)
That means we'd need a million mag 4.1 quakes to relase the same energy as a mag 8.1 -- and like I said, that would only work if they were in the
right region and fault system to do that.
But when we consider that just oine single mag 4.0 releases as much energy as 1,000 mag 2.0 quakes, we can see the relative value in a more day-to-day
scale of relationships.
Sorry. I'm raving on. I apologize. It's gone 1 am here and can't sleep. Horrible feeling.
But whatever, my feeling is that the "little quakes ease the pressure" is part true and part misleading. They release a little bit of the pressure.
Because what I wrote above assumes a static system, where we have a fixed amount of stress.
But it's not like that. It's kind of like: imagine a dam. It's weakened by something and so we need to relieve the pressure on it. Start running water
away down the slipway. But we can't release enough fast enough, because even as we let water out, there is still other water flowing in.
That's the point I'm really trying to make and doubtless annoying everyone in the process. The little quakes are only releasing some of the stress, a
fraction of what is going in, like letting 100,000 gallons of water per hour out of a dam when there's 250,000 going in. Yes, we're helping to reduce
the rate of stress buildup, but the fact remains that sooner or later that dam will reach its failure point and break anyway. Those little quakes
might be delaying things but they won't stop the big one from happening.
And if there is an 8.1 or close to it, it will release around the same energy as one million mag 4 quakes. All in just a few minutes, and all along
one main fault rupture.
Let's hope it's a good long time before it happens.
EDIT! >>> But you are right in what you say: if there are less little quakes, then it means even less stress is being taken off the faults. I meant to
say that first but got sidetracked. By me...
edit on 24/10/11 by JustMike because: I added an edit.