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← GeographyWhich outcome occurs when increased water saturation weakens subduction zones?
A)Decreased shear strength, triggering megathrust earthquakes✓
B)Elevated mantle viscosity, volcanic eruption cessation
C)Enhanced fault lubrication, increased plate velocity
D)Accelerated sediment compression, methane hydrate release
💡 Explanation
Increased water saturation in subduction zones reduces effective normal stress, enhancing pore pressure and reducing the shear strength via the mechanism of effective stress. Therefore, large, infrequent megathrust earthquakes are more likely, rather than changes in mantle viscosity due to different compositional reasons.
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