There was a discussion on some list about the possibility of an
aftershock in half or full synodic month for recent 7+ quake in NZ.
Let me post my message here. I'll post it in few minutes on that list
.
> As before - none of these say "tidal forces CAUSE quakes" - but all relate
> to apparent relationships between quake timings and tidal forces. Type of
> quake and effect and ... vary.
>
Occam's razor tells us to be careful about using terms "force" or
"stress" in relation to Earth tides. What we can see and measure is
displacement, but tidal "force" or "stress" are not routinely
measured. There is no need to make up things about it. That's
crucially important.
As for me, there is the difference between two phrases: "tidal forces
cause quakes" and "periodic tidal deformations pump up quakes" The
first phrase just does not sound convincing. But the second one seems
to fire up some pattern in human brain. Periodic deformations of a
heavily heterogeneous Earth body, - different rigidity, different
phases of state, temperature gradient etc, - should not it result in
some sort of ruptures?
Some would say mantle convection drives plate tectonics, thus causing
quakes. I'd reply - How do you know? Do you see it, can you measure it
directly? What's the necessity to make the things up? You can measure
Earth body deformations, play with this real thing first before
jumping on made up imaginary train called mantle convection.
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