The European Space Agency released a satellite image that shows the upheaval left behind by the pair of earthquakes that rocked Venezuela last week.
The image was created using observations from the Sentinel-1 satellites, which are part of the European Copernicus program. These satellites do not take conventional photographs; instead, they use their radars to “illuminate” the Earth’s surface and record the time it takes for the signal to return to the sensor. By comparing two measurements of the same location taken on different dates, scientists can determine whether the ground has shifted, even when that shift is too small to be seen with the naked eye.
To create the map, scientists compared an observation taken on June 18—one week before the earthquakes—with another taken on June 25, the day after the pair of earthquakes that were mangitude 7.2 and 7.5 respectively. This comparison allowed them to construct what’s known as an interferogram revealing how much the ground deformed following the event.
The ESA explains that what stands out in the map are the repeating colored bands that form horizontal rows in the north. Each complete repetition of the sequence—blue, green, yellow, red, and blue again—represents a fixed increase in the change in distance between the satellite and the ground. The more complete cycles that appear between one area and another, the greater the cumulative ground displacement.
The pattern of bands observed in the northern part of the map corresponds to the region at the epicenter of the earthquakes, which is also where the main deformation occurred. The bands roughly follow the path of the San Sebastián fault system, one of the main tectonic structures in northern Venezuela. The ESA estimates that the displacement in the region was on the order of 30 centimeters (12 inches).
That doesn’t necessarily mean the ground rose or fell by 30 centimeters, though. Earthquakes can cause ground to rise, fall, or move laterally—or some combination of all these movements. An interferogram detects overall changes, not which direction it shifted. That will require different types of imagery as well as on-the-ground surveys. The latter is unlikely to happen for a while, though, as Venezuelan authorities and international partners rush to respond to the growing humanitarian crisis amidst collapsed buildings and destroyed infrastructure.
Space agencies and data processing centers around the world have joined forces to share information that can help with recovery efforts. NASA, for example, activated its Disaster Response Coordination System to identify key risk sites.
This story originally appeared on WIRED en Español and has been translated from Spanish.
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