A satellite’s-eye-view of land warped by earthquakes

The European Space Agency’s Sentinel satellites scan the planet’s bumps and dips with radar vision, pinging signals to the surface and measuring the time it takes for them to return.

This way, they map and monitor phenomena such as sea ice extent, oil spills and land deformed by earthquakes to an accuracy of a few centimetres.

Radar scans from 20 August (Sentinel-1B) and 26 August 2016 (Sentinel-1A) show how the land rose and warped resulting from the 24 August earthquake that shook central Italy. 

Each colour “fringe” corresponds to a few centimetres of surface deformation. Adding the fringes gives scientists an idea of the total amount of ground movement, and in this case, it came to around 20 centimetres of shifting.

The satellites whiz around the planet in a polar orbit – that is, their path loops them up and over the poles – covering the entire Earth’s surface in just six days. On Sentinel-1A’s next pass, it will cover the black and white area to give a complete view of the region.

While Sentinel-1B is pretty new – it was launched in April this year – Sentinel-1A has been an eye in the sky since April 2014.

So when an 8.3-magnitude earthquake struck the coast of central Chile, triggering tsunami warnings and coastal evacuations, on 16 September 2015, Sentinel-1A’s scans before and after (above) showed how the powerful earthquake shook the boundary of the Nazca and South American tectonic plates.

By counting the coloured fringes, scientists estimated that the earthquake caused a displacement of 1.4 metres.

The 25 April 2015 earthquake in Nepal killed more than 8,000 people and injured more than 21,000 – the worst natural disaster to strike the country in 80 years.

Sentinel-1A’s scans – above – from 17 and 29 April 2015 show around 12,000 square kilometres shifted in the earthquake – half of which uplifted and the other half, north of Kathmandu, subsided. 

The biggest earthquake in 25 years struck California’s Napa Valley in the early hours of 24 August 2014.

Two Sentinel-1A images from 7 August and 31 August over this wine-producing region showed maximum ground deformation of more than 10 centimetres.

The image also clearly maps the infamous San Andreas Fault running along the coastline.