Summary
The density of a subducting plate is shown to become greater than the density of the adjacent mantle rock at a subduction depth on the order of 60 km. The density increase results from high pressures generated within the plate during its motion into mantle rock whose long-term strength is much less than the long-term strength of the plate. This positive density contrast between the plate and mantle is in addition to any positive density contrast that may result from the plate not being in thermal equilibrium with the adjacent mantle rock. The effect of this pressure induced density contrast on the overall down-dip stress distribution in the plate is shown to be insignificant on earthquake formation except, possibly, near the upper, near-surface portions of the plate. Implications of this result in terms of the inclusion collapse theory of deep earthquakes are discussed.
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Brady, B.T. Pressure overloads within a subducting plate and the density contrast between the plate and mantle: Some geophysical implications. PAGEOPH 114, 469–477 (1976). https://doi.org/10.1007/BF00876946
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DOI: https://doi.org/10.1007/BF00876946