This project aims to take advantage of a new satellite mission to extract 3-D displacement maps for volcanoes and slowly-deforming tectonic regions, by combining the new data with data from existing missions. These measurements will be used to better understand volcanic plumbing systems and improve estimates of earthquake hazard.
Radar Interferometry (InSAR) is a technique that provides measurements of surface displacement from space, with centimetre-to-millimetre accuracy. These measurements are used in the natural hazards community for measuring tectonic strain rates, estimation of fault slip during earthquakes, and monitoring of volcanoes and landslides. They are also used for monitoring of anthropogenic activities such as oil and gas extraction and drawdown of underground water storage.
The UK Centre of Excellence, COMET, which is led from the University of Leeds, has an ongoing effort to monitor volcanic deformation globally, and to provide alerts when deformation rates change or new deformation appears. Another aim is to use long time series of regular radar acquisitions to measure tectonic strain rates with sufficient accuracy to improve earthquake hazard maps.
1-D to 2-D
InSAR measurements are intrinsically 1-D; they only give the displacement of the ground towards, or away from, the satellite. As radar satellites do not look directly downwards, but off to the side (usually the right), there is a component of both horizontal and vertical motion in the measurements. Therefore, by combining measurements made when the satellite is moving approximately south-to-north with those made when it is moving approximately north-to-south, it is possible to extract a 2-D displacement field. This gives the components of the displacement that lie in an almost vertical plane striking east-west. For right-looking satellites, the plane is tilited slightly from the vertical to dip northwards. The limitation of this is that northward displacement cannot be separated from vertical motion, and motion perpendicular to this plane cannot be measured at all.
2-D to 3-D
In early 2024, NASA and the Indian Space Agency will launch a new satellite mission called NISAR. Unlike other radar satellites, it will point to the left side, and hence be sensitive to displacement in a southward-dipping east-west plane. When combined with measurements from right-looking satellites, such as Sentinel-1, this will enable us to extract the full 3-D displacement field. However, there are challenges to overcome. The radio wavelength used by NISAR is longer than that of Sentinel-1 and the noise characteristics are different; the satellites have different sensitivities to phase change during propagation through the ionosphere and to changes in vegetation and soil moisture. The measurements are also made at different times, which makes combination non-trivial when the rate of ground motion varies.
In this project the student will develop an optimal approach to combining data from left- and right-looking satellites to estimate 3-D deformation, both for steady-state processes, such as tectonic strain build up, and also for non-steady-state processes, such as volcanic activity and earthquakes. The student will apply these algorithms to volcano test cases and a region with N-S trending strike-slip faults. The student will also apply the approach to volcanoes globally.
1) Develop an algorithm to estimate 3-D steady-state and episodic deformation rates by combining left-looking and right-looking satellites
2) Apply the approach to volcano test cases, including those with significant N-S motion, such as Kilauea, Hawaii.
3) Apply the approach to a region with N-S trending strike-slip faults, for example the West-Lut fault in eastern Iran, and estimate the strain rate for the region.
4) Extend the method to volcanoes globally.