Measuring Ground Deformation Using Interferometry

Abstract

The 2018 earthquake near Big Island, Hawaii caused landslides and ground deformation along the east coast. Ground deformation from seismic activity is of interest to scientists as it gives indications of volcanic activity below the Earth’s surface. Measuring this deformation can be challenging and typically requires Global Positioning System (GPS) monitors in place prior to an event to measure change, however, radar satellites provide a clear picture of wide scale movements. Interferometric Synthetic Aperture Radar (InSAR) is a collection method that compares Synthetic Aperture Radar (SAR) collections to measure vertical and horizontal ground displacement. This paper will outline the processes and methods used to process raw SAR data into an interferogram, a deformation map that precisely measures the ground shift after seismic events, glacial movements, or biomass change. Processing an interferogram started with reading raw radar collections from a SAR satellite such as Sentinel-1 and subsequently applying a series of conversions and transformations to create measurable data in the form of a displacement map. The calculated displacement indicates ground a sinking or downslope movement of -0.405 meters over the most active seismic area in Hawaii. The result from the interferogram and displacement map quantifies the effects of seismic activity and how InSAR can be used to accurately measure deformation for use in planning safe urban and infrastructure growth in areas of seismic activity.