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North American dynamics and western U.S. tectonics
Author(s) -
Humphreys Eugene D.,
Coblentz David D.
Publication year - 2007
Publication title -
reviews of geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 8.087
H-Index - 156
eISSN - 1944-9208
pISSN - 8755-1209
DOI - 10.1029/2005rg000181
Subject(s) - plate tectonics , geology , asthenosphere , craton , mantle (geology) , seismology , tectonics , intraplate earthquake , drag , geophysics , lithosphere , tectonophysics , shear (geology) , paleontology , mechanics , physics
Interest and controversy exist on the origin of forces that move and tectonically deform plates, especially regarding the relative importance of loads applied to the plate margins and base and those created internally (e.g., by elevated potential energy in uplifted regions). To quantify these loads, we evaluate predicted interplate stress through two‐dimensional finite element analysis of the North American plate, finding that boundary loads are most important, followed by internal and basal loads. Craton root basal drag of ∼4 MPa opposes absolute plate motion, compared to basal tractions elsewhere that average ∼0.4 MPa, suggesting that North America is separated from a relatively static deep Earth mantle by a weak asthenosphere. San Andreas shear (∼1.5 TN/m), gravitational collapse, and southern Cascadia pull all contribute importantly to western U.S. deformation; the region also is relatively weak. Important future work includes incorporating three‐dimensional plate structure onto global flow calculations and including the global set of plates.