Using vertical deformations of the earth determined by GPS to estimate earth properties and loads on the earth

SMALLEY, ROBERT; BEVIS, MICHAEL; SKVARCA, PEDRO; KENDRICK, E ; LENZANO, LUIS; LENZANO M. G

Workshop; Workshop Internacional La Geomática en las Ciencias de la Tierra; 2012

Earth's crust and lithosphere support loads through two physical mechanisms, elasticity and isostasy. If the load is known, Earth?s response can be used to estimate the physical properties of the crust, lithosphere and mantle involved in the response. Conversely, if the Earth?s properties are known, the response can be used to ?weigh? the load. GPS technology has sufficient precision to measure the vertical and horizontal deformation signals of the Earth associated with surface loading applied by rivers, lakes, and glaciers. We present an examplefrom GPS measurements performed during the past 17 years in the area of the Southern and Northern Patagonian Ice Fields of Chile and Argentina. The GPS network is composed of ~60 campaign sites and ~10 continuous sites that provide a dense, 2-D sampling of the deformation field associated with ice mass changes in the. A sparse regional network is used to define the vertical component of the geodetic reference frame. We process dual frequency GPS phase data using precise orbits and GAMIT/GLOBK. We observe a rapid, broad, pattern of crustal uplift that can be modeled as the glacial isostatic adjustmentto recent ice mass loss of athin lithosphereover a lowviscosity mantle,that is the result of subduction of the Chile Ridge beneath the region. Non-secular vertical and horizontal displacements, representing the elastic response of the crust to changes in current ice mass variations and other loads, are also observed in continuous GPS time series.