Postseismic Viscoelastic Rebound

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Science  18 Jan 1974:
Vol. 183, Issue 4121, pp. 204-206
DOI: 10.1126/science.183.4121.204


The sudden appearance of a dislocation, representing an earthquake, in an elastic layer (the lithosphere) overriding a viscoelastic half space (the asthenosphere) is followed by time-dependent surface deformation, which is very similar to in situ postseismic deformation. The spectacular postseismic deformation following the large Nankaido earthquake of 1946 yields for the asthenosphere a viscosity of 5 x 1019 poise and a 50 percent relaxation of the shear modulus. Large thrust type earthquakes may provide, in the future, a new method for exploring the rheology of the earth's upper mantle.