Global Stress Variation over Time

Abstract:

Understanding how stress changes over time is important as it is related to studies of earthquake triggering and mantle rheology. We calculate stress variation at the Earth’s surface on the global scale from 2003 to 2014, resultant from several major physical forces acting on the Earth. The physical forces we considered include the surface loading due to terrestrial water storage (TWS), force associated with post-glacial rebound (PGR) and tidal loading (including solid tide and ocean tide). The stress change associated with TWS is calculated in this way: we infer TWS from monthly gravity field of the Gravity Recovery and Climate Experiment (GRACE), in which gravity variation associated with PGR has been removed; we then estimate stress change at the Earth’s surface as the elastic response of the GRACE-inferred TWS change. The stress change associated with PGR is calculated as the rate of viscoelastic stress change responding to ice loading from ICE-5G model. And, tidal stress is calculated as the elastic response of the Earth to the traction forces of the Sun and the Moon (solid tide) and to the loading of ocean tide. The total stress change is the sum of the stress changes associated with these three types of forces. As first result, in the study period from 2003 to 2014, the radial normal stress variation exhibits a prominent decreasing trend in southern Africa and Queen Maud Land of Antarctica, an increasing trend in Alaska of the US (United States), Greenland and Marie Byrd Land of Antarctica, and strong annual cycles in southern Africa and Alaska of the US. We will present the geographical distribution of global stress variation from 2003 to 2014 and discuss its possible implications.