| We propose to use time-varying gravity data from the GRACE satellite in a novel way, to monitor relaxation of the solid earth following large earthquakes. The continuous spatial data cover-age will be a first in the solid earth sciences and of particular relevance because major earthquakes occur along oceanic shores. We aim to use these new data to resolve a significant controversy about stress relaxation in the outer few hundred km of the earth; previous studies of post-seismic deformation appear to be at odds with results from rock mechanical laboratory experiments. This issue is fundamental for our understanding of the seismic cycle (loading, slip, relaxation) of major earthquakes. We will focus our attention on a number of recent large earthquakes. Through the combination of different models of postseismic deformation and optimally filtered regional GRACE solutions, we will explore the physics of the stress relaxation processes induced by each seismic event. This approach has already provided interesting results for the case of the 2004 Sumatra earthquake, while the application to other regions will be a prime. One of the main purposes of this research will be to constrain relaxation models that are compatible with laboratory results. |
