"Usually, when you shear clay-rich fault rocks in the laboratory in the way
rocks are sheared in a fault, as the speed increases, the rocks become
stronger and self arrests the movement," said Saffer. "Matt noticed another
behavior. Initially the rocks reacted as expected, but these clays got
weaker as they slid further. They initially became slightly stronger as the
slip rate increased, but then, over the long run, they became weaker."
rocks are sheared in a fault, as the speed increases, the rocks become
stronger and self arrests the movement," said Saffer. "Matt noticed another
behavior. Initially the rocks reacted as expected, but these clays got
weaker as they slid further. They initially became slightly stronger as the
slip rate increased, but then, over the long run, they became weaker."
If I remember my mineralogy, the clay mineral grains are plate-shaped and tend to orient with their flat sides horizontal. They might also have static electric charges that cause them to orient symmetrically and gives them some strength when they are tightly packed. They could resist forces that tend to disrupt their orientation up to the point where their organization is destroyed, at which point they would lose their coherence, and thier resistance.
I don't know, but it makes a good story.
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