On 25 April, a 7.8-magnitude earthquake struck Nepal, claiming over 5000 lives and affecting millions of people. Satellite images are being used to support emergency aid organisations, while geo-scientists are using satellite measurements to analyse the effects of the earthquake on the land.
Radar imagery from the Sentinel-1A satellite shows that the maximum land deformation is only 17 km from Nepal’s capital, Kathmandu, which explains the extremely high damage experienced in this area.
By combining Sentinel-1A imagery acquired before and after the quake, changes on the ground that occurred between the two acquisition dates lead to rainbow-coloured interference patterns in the combined image, known as an ‘interferogram’, enabling scientists to quantify the ground movement.
The ground has shifted beneath Nepal’s feet, and space agencies around the globe are rushing to measure it…Using satellites that bounce radar waves off the earth and listen to the echo, scientists are able to calculate the distance between those satellites and the earth. Comparing the measured distances before and after the earthquake shows how much the earth has changed shape.
This type of measurement isn’t perfect. Radar can be scattered by snow and heavy vegetation, according to NASA, making areas covered with those features hard to compare. Satellites also don’t look straight down on all areas of the earth, but at an angle while they orbit from pole to pole.
World Food Program which coordinates the distribution of food and other relief goods regularly publishes a report compiled by its Nepal Food Security Monitoring System (NeKSAP) field teams added with other relevant info. Click on the image below for access to the currently latest update:
Another very useful resource for those in the field is HDX, a collaboration between UN OCHA and a design firm to create a user friendly data sharing platform, described in this article on Fastcompany.