When earthquakes suddenly strike, Earth shakes, rattles, and rolls, and NASA springs into action. Using both airborne instruments and orbital satellite constellations that peer down from their remote spaceborne perches, specialists in NASA’s Disasters Program crunch data to develop visualizations — maps, images, and detailed graphics – that support search and rescue efforts. Such information can point emergency responders to areas most affected, and inform decision-makers on where and how to direct disaster relief to the neediest communities.
About 50 earthquakes – also known as quakes, tremors, or temblors – occur each day around the world. Earthquakes are caused by a sudden release of energy in the Earth's crust as the world’s enormous tectonic plates rub against one another, creating seismic waves. Although most earthquakes don’t have a noticeable effect on life and work, large-magnitude quakes near cities and towns can cause catastrophic devastation, destroying buildings and infrastructure — and, in some cases, taking thousands of lives.
Earthquakes that occur near coastlines or under oceans can also generate tsunamis with waves over 100 feet high that can sweep away anything in their path and quickly ravage communities. Immediately following an earthquake, aftershocks (subsequent smaller earthquakes) may continue for weeks, causing additional damage and hampering recovery.
On July 4 and 5, 2019, two large-magnitude earthquakes struck near Ridgecrest, California, generating surface ruptures and damaging homes and businesses. A NASA Disasters Program research team conducted a series of drone flights to map the post-quake changes in topography and terrain in three dimensions.
NASA satellite imagery had already revealed land deformation, including surface ruptures and ground displacement. Although the information derived from orbiting instruments is indispensable, bringing aircraft into the equation sharpens the view. Data derived from airborne observation nearer the ground has a higher resolution and often reveals additional details not initially apparent.
In particular, synthetic aperture radar (SAR) can “see” how the ground below has changed, and researchers use this data to create 3D images. These images are analyzed and compared to pre-existing visualizations to produce interferograms — maps that highlight disturbed geographical features and vividly demonstrate changes in topography.
The Advanced Rapid Imaging and Analysis (ARIA) team—which is affiliated with NASA’s Disasters Program and based at the Jet Propulsion Laboratory in Pasadena, California—also uses SAR-derived data collected by the European Space Agency’s Copernicus Sentinel 1-A satellite. Information gathered in this way isn’t affected by cloud cover and can be acquired day or night. ARIA researchers have used SAR in disaster management support during a number of earthquake responses around the world.