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Broadscale Postseismic Gravity Change Following the 2011 Tohoku-Oki Earthquake and Implication for Deformation by Viscoelastic Relaxation and AfterslipThe analysis of GRACE gravity data revealed post-seismic gravity increase by 6 micro-Gal over a 500 km scale within a couple of years after the 2011 Tohoku-Oki earthquake, which is nearly 40-50% of the co-seismic gravity change. It originates mostly from changes in the isotropic component corresponding to the M(sub rr) moment tensor element. The exponential decay with rapid change in a year and gradual change afterward is a characteristic temporal pattern. Both viscoelastic relaxation and afterslip models produce reasonable agreement with the GRACE free-air gravity observation, while their Bouguer gravity patterns and seafloor vertical deformations are distinctly different. The post-seismic gravity variation is best modeled by the bi-viscous relaxation with a transient and steady state viscosity of 10(exp 18) and 10(exp 19) Pa s, respectively, for the asthenosphere. Our calculated higher-resolution viscoelastic relaxation model, underlying the partially ruptured elastic lithosphere, yields the localized post-seismic subsidence above the hypocenter reported from the GPS-acoustic seafloor surveying.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Han, Shin-Chan
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Sauber, Jeanne
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Pollitz, Fred
(Geological Survey Menlo Park, CA, United States)
Date Acquired
November 30, 2016
Publication Date
August 28, 2014
Publication Information
Publication: Geophysical Research Letters
Publisher: Wiley Publications
Volume: 41
Issue: 16
Subject Category
Geosciences (General)
Report/Patent Number
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