Modelling vertical displacements due to hydrological load at stations of the Geocentric Reference System for the Americas (SIRGAS)

BRUNINI, CLAUDIO; SÁNCHEZ L.; GALVÁN, ROMINA; DREWES, HERMANN; GENDE, MAURICIO

Kobe

Conferencia; IAG-IASPEI 2017 Joint Scientific Assembly; 2017

International GNSS Service

This study concentrates on modelling seasonal vertical motions caused by variations of the hydrological load at geometrical reference frame stations. The proposed model relates the response of the Earth´s crust (as measured by GNSS) to the hydrological load (inferred from GRACE). It is based on a numerical solution of the static equilibrium equation for an elastic medium (i.e. the Earth´s crust) characterized by an elastic parameter. The elastic parameter relies on the combination of Poisson?s ratio and Young?s modulus. The empirical experiments combine (a) the normal equation systems (NEQ) calculated on a weekly basis for the SIRGAS reference frame along five years, with (b) monthly grids of equivalent water height (EWH) derived from GRACE for the same time span. The solution of the combined NEQ leads to the common adjustment of seven parameters per GNSS station; namely, three position coordinates at a certain epoch, three constant velocity coordinates, and one elastic parameter. The vertical positions predicted after the adjustment agree with the SIRGAS weekly positions within ±3 mm at the one sigma level. This is interpreted as a first satisfactory evaluation of the capability of this method.