Open AccessEffect of viscosity structure on fault potential and stress orientations in eastern Canada
Author(s) -
Wu Patrick
Publication year - 1997
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1997.tb05653.x
Subject(s) - deglaciation , geology , seismology , viscoelasticity , mantle (geology) , lithosphere , stress field , stress (linguistics) , geophysics , geodesy , holocene , tectonics , oceanography , materials science , physics , thermodynamics , linguistics , philosophy , finite element method , composite material
SUMMARY Previous investigations of the causal relationship between postglacial rebound and earthquakes in eastern Canada have focused on the mode of failure and the observed timing of the pulse of earthquake/faulting activity following deglaciation. In this study, the observational database has been extended to include observed orientations of the contemporary stress field and the rotation of stress since deglacial times. It is shown that many of these observations can be explained by a realistic ice history and a viscoelastic earth with a uniform 10 21 Pa s mantle. The effects of viscosity structure on the above predictions are also examined. It is shown that, since most of the above observations are found within the ice margin, they are not very sensitive to lithospheric thickness. Also, the inclusion of a 25 or 50 km ductile layer within the lithosphere will not decouple the seismogenic upper crust. High viscosity (10 22 Pa s) in the lower mantle is rejected by the stress orientation and rotation observations. A low‐viscosity (6 times 10 20 Pa s) upper mantle with 1.6 times 10 21 Pa s in the upper part of the lower mantle and 3 times 10 21 Pa s in the lower part of the lower mantle below 1200 km depth has been found to give predictions that are in general agreement with the observations.