Satellites Measured 60 Centimeters of Ground Shift: NISAR Reveals the Full Force of Venezuela’s Twin Earthquakes
Featured image: NISAR interferogram showing ground displacement from the June 24 Venezuela earthquakes. Credit: NASA Earth Observatory/Lauren Dauphin, data from Eric Fielding/NISAR science team at JPL
When twin earthquakes struck northern Venezuela on June 24, the ground moved. How much it moved, and where, had to be measured from space. The answer, provided by NASA’s NISAR satellite within 24 hours of the quakes, was up to 60 centimeters (24 inches) of westward displacement along the fault section nearest Caracas and La Guaira.
The first earthquake, magnitude 7.2, struck near San Felipe at approximately 6 p.m. local time. Thirty-nine seconds later, a magnitude 7.5 mainshock hit near Yumare. It was the strongest earthquake to hit Venezuela since 1900. Together they killed more than 1,700 people, injured some 5,000, and damaged or destroyed approximately 58,870 buildings, concentrated along the coastal La Guaira state and the capital Caracas.
NISAR, the NASA-ISRO Synthetic Aperture Radar mission launched in 2024, was overhead. For the first time, its Urgent Response (UR) system was activated for a major earthquake, delivering preliminary ground displacement maps within 12 to 24 hours of the event.
InSAR: measuring Earth’s deformation from orbit
The technique, called Interferometric Synthetic Aperture Radar (InSAR), compares two or more radar images of the same area taken at different times. By measuring the phase difference between the images, scientists can detect changes in the distance between the satellite and the ground down to the centimeter scale.
NISAR carries both L-band and S-band radar, viewed at an angle of approximately 40 degrees from vertical. This oblique perspective allows the instrument to capture both horizontal and vertical components of ground displacement. On a strike-slip fault like the one that ruptured in Venezuela, where most of the motion is horizontal, this capability is critical.
The pre-quake images were taken on June 13 and June 18. Post-quake images were acquired on June 25 and June 30. The resulting interferogram shows a vivid map of the rupture: red areas indicate ground that moved east and up, blue areas show ground that moved west and down. A thin band of white near the town of Morón marks the fault rupture at depth, where the two sides slid past each other without measurable displacement.
“The NISAR data shows up to 24 inches of ground movement in the area that was most heavily damaged,” said Eric Fielding, a geophysicist at NASA’s Jet Propulsion Laboratory and member of the NISAR science team. “These are reasons why the damage in Caracas and La Guaira was so extreme. InSAR tells us a lot about what happened during this earthquake.”
A new capability for disaster response
The Urgent Response system is designed to do exactly what it did for Venezuela: provide rapid, actionable data to disaster response teams without waiting for weeks of precise orbit determination. The system uses predicted orbit data to produce preliminary maps within a day, then reprocesses them with precise orbit data one to two days later.
The USGS subsequently used the NISAR data to refine its finite fault model of the earthquake, producing a more accurate picture of how the rupture propagated along the fault. “That is extremely helpful for the people who need to understand why damage was so severe in that area,” Fielding said.
ESA’s Copernicus Sentinel-1 satellite, which carries a C-band SAR, also produced interferograms showing approximately 30 centimeters (12 inches) of line-of-sight displacement from the same event. The combination of L-band (NISAR) and C-band (Sentinel-1) data gives seismologists a more complete picture: L-band radar can penetrate vegetation and dry sand to measure ground motion in areas where C-band cannot.
The fault that has been waiting to break
The earthquakes occurred on the San Sebastián fault system, part of the Caribbean-South American plate boundary. Scientists have long known these faults were accumulating strain. The rupture propagated offshore toward the east, then back onshore near the international airport north of Caracas, which helps explain why the capital region saw such severe damage despite being slightly farther from the epicenters.
NASA’s Disasters Response Coordination System coordinated the satellite-based assessment, while a separate damage assessment by researchers Corey Scher and Jamon Van Den Hoek at Oregon State University used Sentinel-1 radar to estimate the building damage count.
For the NISAR mission, the Venezuela response was a test of a capability that will be needed again. The satellite’s global coverage and rapid revisit time mean it will be the first eyes in the sky for many of the world’s next major earthquakes. The data it returned in June proved the concept works, and it worked fast enough to matter. The ground in Venezuela shifted 60 centimeters. From orbit, NASA saw every centimeter.