Tuesday, February 7, 2023

Edge effects in fault mechanics

 When you test rock samples in a big machine, you see the fracture patterns.  This was my background in rock mechanics.  Geotechnical engineering and rock mechanics is a dead field now, because everybody and their dog thinks they can do it.  This has led to amazing failures.  The same goes for basic physics.

If you compress a rock sample you'll will get 'triplet' failure.  That's a thrust (compression) failure with wings of strike-slip or shear.  Usually the shear failure starts first.  Rock is 'scale invariant' or 'fractal similar' from the crystal scale, to the tectonic plate scale.  That means you can project small rock failures to large earthquakes -- it's all the same.  As an example you always put a scale on your rock photos because you can't tell the difference between large and small.

The New Madrid earthquake zone is failure in a very large testing machine.  There is the central thrust and two shear wings.  This is now stable for hundreds of years.  The central thrust created two points of high shear stress and this was taken care of by the wings which fade with distance.  The area continues to take in water, and is always active, but it is stable.

New Madrid was in a uniform stress field of high compression.  Turkey is in a complex wrench situation, and we don't know the stress field.  Nevertheless, the edges must crack out.  This is tension (pulling) rather than compression (squeezing).  It has led to an unusual intersection at the top.  Both sections are wrenching each other open, and the 'fade out' starts at the middle.  I fought with my brain to not go into a 'brain storm' over this while I slept, and it's working.  I'm not killing myself for an original thought.

For this triplet to  be complete, we need another monster earthquake at the bottom and parallel to the upper section.  But the existing fractures interfere, and the stress field is not uniform.  I only give it a 20% chance for the next week or two, like New Madrid.  More physics could be done, but we live in a world of dogma, and no Scientific Method.

Earthquakes and the atmosphere are exactly the same physics.  We haven't had 'newsworthy' earthquakes for 30 years now, so I went into atmospheric physics.  

The lack of physics in both fields will lead to big disasters, as the groupthink shakes out.  I'm contemplative right now, and forcing myself to relax.

ps.  we now have to find out how these faults ruptured.  If it initiated at the intersection, and the rupture to the south had a fade-out, then less chance of a new rupture.  If it initiated at the water, then a greater chance.

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