Which mechanical effect primarily initiates deep-focus earthquakes within subducting lithospheric slabs?

💡 Explanation

When a subducting slab descends, dehydration embrittles the rock matrix because water is released from minerals undergoing phase transitions, raising pore pressure and lowering effective strength. Therefore, dehydration embrittlement initiates deep-focus earthquakes, rather than melting, magnetism or tides, which have significantly lower impact at those depths.

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