After a massive 8.3 earthquake rocked Chile’s northern coast on September 16, scientists immediately began analysing satellite images taken before and after the temblor to get a good idea of how far the ground moved.
This technique — called Synthetic Radar Aperture Interferometry (InSAR) — combines before and after satellite images into colourful maps — called interferograms.
The rainbow-coloured fringes, which can be similarly interpreted as the elevation contours on a map, help scientists approximate how far the ground moved on a fault following an earthquake. The European Space Union launched the spacecraft that took these images, called Sentinel-1, in the spring of 2014. It orbits about 430 miles above Earth and uses radar to sense ground movements.
After an initial analysis, scientists were able to calculate that the ground moved about 140 cm away from the satellite in the region falling between the quake’s epicentre — about 10 miles off the coast of Chile — and the edges of the affected area, Petar Marinkovic, a scientist who computes interferograms for the Laboratories For Processing Planetary Observations in the Netherlands, told Tech Insider in an email.
As of September 17, the Chile quake, which sparked tsunami warnings as far away as Hawaii and California’s coast, has killed 11 people. The region is particularly seismically-active, and has endured three major earthquakes higher than a magnitude 8 in the past five years.
In addition to helping scientists quantify exactly how far the ground moved during a quake, interferograms also create geophysical models of quakes and aid in relief efforts.
These particular satellites also help scientists keep tabs on sea ice, oil spills, winds and waves in the ocean, changes in land-use, and help in emergency response following floods and earthquakes.
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