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

Introduction

Interferometric synthetic-aperture radar (also known as 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.

Background Information

The 2016 Kaikoura earthquake was a magnitude 7.8 (Mw) earthquake in the South Island of New Zealand that occurred two minutes after midnight on 14 November 2016 NZDT (11:02 on 13 November UTC). Ruptures occurred on multiple faults and the earthquake has been described as the "most complex earthquake ever studied". Wikipedia-2016 Kaikoura earthquake

On 12 November 2017 at 18:18 UTC (21:48 Iran Standard Time, 21:18 Arabia Standard Time), an earthquake with a moment magnitude of 7.3 occurred on the Iran–Iraq border, with the Iraqi Kurdish city of Halabja, and the Kurdish dominated places of Ezgeleh, Salas-e Babajani County, Kermanshah Province in Iran, closest to the epicentre, 30 kilometres (19 mi) south of the city of Halabja, Iraqi Kurdistan. Wikipedia-2017 Iran–Iraq earthquake

Brief explanation of interferogram: The coloured fringes map the deformation of the surface of the Earth in the direction of the view from the satellite in units of the radar wavelength (2.8 cm) between colour cycles. esa-interferometry

Sentinel-1 Data and Software

Table 1: Data Acquisition

Data	Data Time	Data Download Link
Before 2016 Kaikoura earthquake	2016 Nov. 03	esa download link Full name: S1A_IW_SLC__1SSV_20161103T072220_20161103T072250_013774_0161F9_2F68.
After 2016 Kaikoura earthquake	2016 Nov. 15	esa download link Full name: S1A_IW_SLC__1SDV_20161115T072214_20161115T072244_013949_016775_84CF.
Before 2017 Iran–Iraq earthquake	2017 Nov. 11	esa download link Full name: S1A_IW_SLC__1SDV_20171111T150004_20171111T150032_019219_0208AF_EE89.
After 2017 Iran–Iraq earthquake	2017 Nov. 17	esa download link Full name: S1B_IW_SLC__1SDV_20171117T145926_20171117T145953_008323_00EBAB_AFB8.

System Requirements	SNAP Download
Windows or Mac OS X Requires at least 16 GB memory RAM A Solid State Drive, as opposed to Hard Disk Drive, will speed up processing Close other applications Do not use the computer while a product is being processed Remove the previous product once a new product has been generated.	Sentinel-1 Toolbox - The current version is 7.0.0 (22.07.2019 13:30 UTC). Download Link (Version depends on your working environment!)