Geodesy Group - Emma Hill

Overview

Geodesy is a highly interdisciplinary science with significant application to understanding risks to society from natural hazards and climate change. It is commonly defined as the study of the Earth’s shape, size, gravity field, and how these parameters change over time.

Sources of geodetic information include tide gauges for measuring relative sea-level height, continuously operating Global Positioning System (GPS) receivers and Interferometric Synthetic Aperture Radar (InSAR) for measuring displacements of the Earth’s crust, and the GRACE satellite mission, which takes monthly snapshots of the Earth’s gravity field. These data sets together enable measurement of processes in the Earth system that include, amongst others, crustal deformation from tectonics and earthquakes, changes in sea level, volcanic deformation, melting glaciers, and changes in continental water storage.

With the advent of space-borne geodetic technologies, the quantity and spatial resolution of geodetic data have increased dramatically, and they continue to do so. Data precision has also increased dramatically, so we now need to understand not only the primary process affecting a measurement, but also many secondary processes that affect the measurements on a fine scale. For example, the gravity field at a single location can be affected by changes in nearby glaciers, hydrology, sea level, and tectonics, as well as measuring the ghosts of past ice sheets in the form of glacial isostatic adjustment.  

A focus of much of our research, therefore, is to combine multiple different geodetic data sets together to help separate the different signals in the data, and to provide better-constrained models for processes such as earthquakes and sea-level change. To place emphasis on the association of uncertainties with our results, we are investigating various techniques for Bayesian combination of data and models.

One of our primary data sets is the Sumatra GPS Array (SuGAr). This is a 48-station continuous GPS network maintained by EOS, designed to monitor tectonic deformation and earthquakes along the Sumatra subduction zone.  This network has recorded a huge number of large earthquakes over the last decade, and much of our recent work has focused on separating the effects of these different earthquakes in the time series, and studying their rupture histories. We are currently working on code to analyze the evolution of fault slip during the earthquakes, through inversion of high-rate (1-second sampling) GPS data.  

Latest Projects

Illustration of waveglider motion

Barbot's team is developing geophysical marine robots to probe the deformation of the seafloor. The end goal is to extend geodetic measurements offshore to better understand earthquakes, tectonic processes and tsunami hazards.

Combining various sources of geodetic data, including GPS and InSAR, to study natural hazards in Southeast Asia. Studies include earthquake and tsunami hazards of Indonesia and Myanmar, and regional sea-level change due to tectonic deformation....

This project aims to assess sea level variability during the Holocene with precise and accurate data.

The Gravity Recovery and Climate Experiment (GRACE) provides monthly snap-shots of earth’s gravity field, which are used to estimate regional variations in sea-level.

Studies focused on tectonic activity along the Sumatran Fault zone (SFZ), which traverses the entire 1900-km length of Sumatra, are still lacking. The SFZ is segmented and the slip rate varies for each segment, but rates are poorly known,...

SuGAr has been observing surface deformation in Sumatra since 2002.

Awards

2016

AGU 2016 Geodesy Section Award

Collaborators