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991219921

No, It means that the tension between tectonic plates steadily builds up, so an earthquake is more likely.

I see - the article though seems to talk about 'surface-breaking' earthquakes occurring every 100 years in that region, and that we're now at 159 years without one.

This idea of a time expectation doesn't seem to match your explanation (which seems more intuitive to me).

They're the same, really -- those quakes happen every 100 years because that's how long it takes for that much pressure to build up. 159 years without one means there's already going to be quite a lot of pressure built up that's going to have to give way sooner or later.

We know that fluid injections for fracking can cause earthquakes.

How about injecting some extremely viscous fluid deep underground within the plate boundaries?

So it can release the shear force over months or years rather than seconds. Something like pitch (https://en.wikipedia.org/wiki/Pitch_drop_experiment)

Of course, the major problem with trying quake mitigation strategies might be the legal responsibility if you cause a quake.

Aside from the very real liability issue, the idea of lubricating faults is interesting. From a practical standpoint it would be hard to inject something that remains viscous enough at the relevant temperatures. Earthquakes nucleate at about 10 km depth in the San Andreas, which is about 350 degrees C. So aside from the difficulty of drilling in these conditions, you would have to have a fluid that maintains its viscosity from surface temperatures to 350 C.

Given fracking injections are a lot shallower than 10km, I'm not sure it would have to be injected that deep. But it's a good point, that temperature will be a factor.

Getting a high-melting-point fluid down there might be done by dissolving or suspending it in water that is allowed to boil off, or having a heated injection pipeline.

Silicone and silicate lubricants are viable at those temperatures. Might not be viscous enough, though.

A low melting phosphate glass might work.

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