ITRF2014: A new release of the International Terrestrial Reference Frame modeling nonlinear station motions

TLDR

ITRF2014 introduces enhanced nonlinear station motion modeling, incorporating seasonal signals and postseismic deformation for earthquake‑affected sites, and makes these deformation models available as part of the frame while estimating annual and semiannual signals internally to refine the secular velocity field. The frame is built from reprocessed weekly, daily, and 24‑hour time series of station positions from VLBI, SLR, GNSS, and DORIS, with the scale defined by the arithmetic average of SLR and VLBI implicit scales, and postseismic deformation parameters derived from GNSS/GPS applied across all techniques. ITRF2014 outperforms previous releases by precisely modeling station trajectories, yielding a robust secular frame, an origin coincident with the Earth system center of mass to within <3 mm at 2010 and <0.2 mm yr⁻¹, scale differences of 1.37 ppb at 2010 and 0.02 ppb yr⁻¹, and high consistency of postseismic deformation models across techniques.

Abstract

Abstract For the first time in the International Terrestrial Reference Frame (ITRF) history, the ITRF2014 is generated with an enhanced modeling of nonlinear station motions, including seasonal (annual and semiannual) signals of station positions and postseismic deformation for sites that were subject to major earthquakes. Using the full observation history of the four space geodetic techniques (very long baseline interferometry (VLBI), satellite laser ranging (SLR), Global Navigation Satellite Systems (GNSS), and Doppler orbitography and radiopositioning integrated by satellite (DORIS)), the corresponding international services provided reprocessed time series (weekly from SLR and DORIS, daily from GNSS, and 24 h session‐wise from VLBI) of station positions and daily Earth Orientation Parameters. ITRF2014 is demonstrated to be superior to past ITRF releases, as it precisely models the actual station trajectories leading to a more robust secular frame and site velocities. The ITRF2014 long‐term origin coincides with the Earth system center of mass as sensed by SLR observations collected on the two LAGEOS satellites over the time span between 1993.0 and 2015.0. The estimated accuracy of the ITRF2014 origin, as reflected by the level of agreement with the ITRF2008 (both origins are defined by SLR), is at the level of less than 3 mm at epoch 2010.0 and less than 0.2 mm/yr in time evolution. The ITRF2014 scale is defined by the arithmetic average of the implicit scales of SLR and VLBI solutions as obtained by the stacking of their respective time series. The resulting scale and scale rate differences between the two solutions are 1.37 (±0.10) ppb at epoch 2010.0 and 0.02 (±0.02) ppb/yr. While the postseismic deformation models were estimated using GNSS/GPS data, the resulting parametric models at earthquake colocation sites were applied to the station position time series of the three other techniques, showing a very high level of consistency which enforces more the link between techniques within the ITRF2014 frame. The users should be aware that the postseismic deformation models are part of the ITRF2014 products, unlike the annual and semiannual signals, which were estimated internally with the only purpose of enhancing the velocity field estimation of the secular frame.