Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
The European Space The agency released a satellite image showing the wake left by a two earthquakes that shook 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 ordinary pictures; instead, they use their radar to “beam” the Earth and record the time it takes for the signal to return to the sensor. By comparing two ground measurements taken on different days, scientists can tell if the ground has moved, even if the movement is too small to be seen with the naked eye.
In order to create a map, scientists compared what they saw on June 18—one week before the earthquakes—with what happened on June 25, the next day. two earthquakes of magnitude 7.2 and 7.5 respectively. These simulations allowed them to create what is known as an interferogram that shows how the ground was deformed after the event.
ESA explains that what appears on the map are colored bands that repeat horizontal lines in the north. Each complete repetition of this process—blue, green, yellow, red, and blue again—represents a constant increase in the change in distance between the satellite and the ground. The amount of rotation that appears between one component and another, also results in downward displacement.
The formation of the bands seen in the north of the map corresponds to the region where the earthquakes occurred, which is also where the most changes took place. These bands follow the path of the San Sebastián fault system, one of the main tectonic features in northern Venezuela. ESA estimates that the displacement in this region was 30 centimeters (12 inches).
