Overview
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.
Resources
Graphics
Map showing SuGAr stations, recent rupture patches on the Sunda megathrust, and volcanoes in Sumatra
Videos
Introduction to the Southeast Asia SEA-Level (SEA2) Program
Facilities
Sumatran GPS Array (SuGAr)
Map showing SuGAr stations, recent rupture patches on the Sunda megathrust, and volcanoes in Sumatra
Segmentation of the SFZ and historical earthquakes. The SFZ has generated many historical earthquakes with magnitude ≥7 (Sieh and Natawidjaja, 2000)
Cross-section of the island of Sumatra, Indonesia