Creating Interferogram for Mapping Earthquake Deformation by using Sentinel-1 Data in SNAP

Introduction

Interferometric synthetic-aperture radar (A.K.A InSAR) is a remote sensing technique of satellite radar. It uses two and more SAR images to create DEM (digital elevation map) in surface deformations based on phase differences, so this technique can be used to monitor hazard Response like earthquake deformation and landslides, volcanic Eruptions and tornado damage.

Synthetic aperture radar (SAR) is an active radar and Sentinel-1 is the first of the Copernicus Programme satellite constellation launched by the European Space Agency, which provides providing continuous all-weather, day-and-night imagery at C-band, weather conditions like clouds won’t affect the quality of image. Active radar doesn’t need illumination from sun, the sensor of satellite can transmit signal and receive backscattered signal shortly, which means it uses the difference between the phase signals from repeatedly detecting earth surface to monitor surface deformation and landcover changes, in another word, the phase differences are from two different observations with minor different sensor position. After combining two images in coregistration step, a basic interferogram will be created.

In this tutorial, we will create two interferograms from two earthquake examples: 2016 Kaikoura earthquake (New Zealand) and 2017 Iran–Iraq earthquake, whose magnitudes are 7.8 and 7.3 respectively, each example has a paired Sentinel-1 data, including image before earthquake and image after earthquake.