Prof. Rowena Lohman of Cornell will present the EAPS Geophysics Seminar, "Moving beyond phase in InSAR - trying to see through soil moisture and vegetation when we study ground deformation.” 

"Interferometric Synthetic Aperture Radar has now been used for decades to study volcanoes, earthquakes, landslides, glaciers, and other deforming features on the Earth's surface. In the early days of InSAR, SAR imagery was often only acquired once every few months, making it difficult to impossible to study areas where the landcover was fairly dynamic (forests, agricultural regions, etc.). With modern missions providing imagery every few days to weeks, we often now can generate interferograms even in areas with intensive agriculture, such as California's Central Valley. Closer inspection of this data shows, however, that the imagery contains many signals that are not produced by ground displacement. Soil moisture variability and vegetation growth also contribute to InSAR observations in ways that we were not able to see in most earlier studies, which focused (by necessity) on areas with very little vegetation.

"I will show some examples of these signals, the potential biases that they can introduce to studies of ground deformation, and some approaches we are exploring to help mitigate these factors. I will show some results from hyperarid regions that experience infrequent but heavy rainfall events - these allow us to separate and understand the effect of soil moisture from the confounding impact of vegetation in a way that we hope to then apply to areas that do have significant vegetation. I will also present results on the use of other observables that we can pull out of the SAR time series and that can support efforts to distinguish ground deformation from all of the other competing factors contributing to the interferometric phase."