Satellites of the European Copernicus Sentinel-1 mission measured the movement and deformation of the earth's surface after the devastating earthquakes in Venezuela with a magnitude of 7,2 and 7,5 using the method of satellite radar interferometry (InSAR). This technology allows you to record even millimeter shifts of the soil, regardless of cloudiness or time of day.
How exactly the measurement process took place?
Radar "illumination" of the territory: Unlike optical satellites, Sentinel-1 does not take ordinary pictures. Its SAR tool (synthetic aperture radar) directs radio pulses to the Earth at a diagonal angle and records the time and phase of the signal, which is reflected from the surface back to the sensor.
Comparison of "before" and "after": Scientists took two sets of radar data of the same area. The first picture was taken 18 June (a week before the disaster), And the second – 25 June, the day after the aftershocks.
Creating an interferogram: By superimposing the phases of these two signals, a special deformation map was formed – interferogram. Changes in the distance between the satellite and the earth were reflected on it in the form of colored interference bands.
What the satellite data revealed Shift scale: Sentinel-1 data showed, that along the Caracas Corridor – In La Guaira, the earth moved approximately 30–40 cm along the line of sight of the satellite.
The nature of the fault: The analysis recorded a right-sided shear deformation pattern. The affected area stretched almost 200 km from San Felipe to the capital.
Epicenter in the sea: Thanks to long-term observations, geophysicists found out, that most of the rupture occurred at sea in the blocked section of the San Sebastian submarine fault.
Damage assessment: In addition to plate motion, radar data was used to quickly create infrastructure damage assessment maps. They made it possible to identify thousands of probably destroyed buildings in Caracas and the surrounding regions.
Combining InSAR radar maps with data from ground-based GPS/GNSS stations allowed Universidad del Zulia scientists to build an accurate three-dimensional model of the, exactly how the earth's crust moved during this earthquake.
Source: https://www.esa.int