EAPSI: The Effect of Seasonal Hydrological Loading on Vertical GPS Time Series

Materna Kathryn, Berkeley CA

Investigators

Abstract

Continuous GPS time series have recently enabled the study of a variety of ground deformation sources. One non-tectonic deformation source, particularly important for vertical GPS time series, is seasonal changes in elastic loading. For example, this can occur when water reservoirs annually cycle between empty and full. If the contributions of water loading to the GPS time series can be modeled and understood, it is possible to make timely, accurate, and locally useful estimates of surface water storage simply from GPS measurements. To that end, this study aims to identify the components of surface water loads in the continuous GPS measurements from Myanmar. The vertical GPS signals in this dataset are known to contain some of the largest annual oscillations in the world, likely due to the Asian Monsoon. However, the degree to which changes in surface water storage can explain the GPS oscillations remains unknown. This work will be completed with Professor Emma Hill, a leading researcher in GPS geodesy at the Earth Observatory of Singapore. This research will also benefit from collaboration with the many researchers in Dr. Hill's research group who are working on a large-scale study of geodetic data from Myanmar. This project will decompose the GPS time series into components from elastic loading and other sources through a loading model. Gravity measurements from the GRACE satellite mission will be used to constrain surface water loads. The elastic deformation will then be modeled for each GPS station using a reference earth structure. It is hypothesized that much of the seasonal variation in the vertical GPS time series, which can reach 5 cm/year in amplitude, is due to hydrologic loading. This project will produce a specific model of the seasonal loading effects on the deformation field. The correlations between the GPS and GRACE time series should also provide locally specific estimates of water storage levels at each continuous GPS station in Myanmar. This award, under the East Asia and Pacific Summer Institutes program, supports summer research by a U.S. graduate student and is jointly funded by NSF and the National Research Foundation of Singapore.