Turns Out Satellites Work Great for Mapping Earthquakes

Skip to story Satellite radar image of the magnitude 6.0 South Napa earthquake.Satellite radar image of the magnitude 6.0 South Napa earthquake. European Space Agency

The Nepal earthquake on Saturday devastated the region and killed over 2,500 people, with more casualties mounting across four different countries. The first 24 hours of a disaster are the most important, and first-responders scramble to get as much information about the energy and geological effects of earthquakes as they can. Seismometers can help illustrate the location and magnitude of earthquakes around the world, but for more precise detail, you need to look at three-dimensional models of the ground’s physical displacement.

The easiest way to characterize that moving and shaking is with GPS and satellite data, together called geodetic data. That information is already used by earthquake researchers and geologists around the world to study the earth’s tectonic plate movements—long-term trends that establish themselves over years. But now, researchers at the University of Iowa and the U.S. Geological Survey (USGS) have shown a faster way to use geodetic data to assess fault lines, turning over reports in as little as a day to help guide rapid responses to catastrophic quakes.

Normally, earthquake disaster aid and emergency response requires detailed information about surface movements: If responders know how much ground is displaced, they’ll know better what kind of infrastructure damage to expect, or what areas pose the greatest risk to citizens. Yet emergency response agencies don’t use geodetic data immediately, choosing instead to wait several days or even weeks before finally processing the data, says University of Iowa geologist William Barnhart. By then, the damage has been done and crews are already on the ground, with relief efforts well underway.
The new results are evidence that first responders can get satellite data fast enough to inform how they should respond. Barnhart and his team used geodetic data to measure small deformations in the surface caused by an 6.0-magnitude quake that hit Napa Valley in August 2014 (the biggest the Bay Area had seen in 25 years). By analyzing those measurements, the geologists determined how much the ground moved with relation to the fault plane, which helps describe the exact location, orientation, and dimensions of the entire fault.

Then they created the Technicolor map above, showing just how much the ground shifted. In this so-called interferogram of the Napa earthquake epicenter, the cycles of color represent vertical ground displacement, where every full cycle indicates 6 centimeters (e.g. between every green band is 6 cm of vertical ground).
According to the Barnhart, this is the first demonstration of geodetic data being acquired and analyzed the same day of an earthquake. John Langbein, a geologist at the USGS, finds the results very encouraging, and hopes to see geodetic data used regularly as a tool to make earthquake responses faster and more efficient.

Barnhart is quick to point out that this method is only meant for moderate earthquakes (between magnitudes of 5.5 and 7.0). Although the Nepal earthquake had a magnitude of 7.8, over 35 aftershocks continued to rock the region, including one as high as 6.7 on Sunday. The earthquake itself flattened broad swaths of the capital city of Kathmandu, and caused avalanches across the Himalayan mountains (including Mount Everest), killing and stranding many climbers. But the aftershocks are stymieing relief efforts, paralyzing citizens with immobilizing fear, and creating new avalanches in nearby mountains.

It’s also worth remembering that the 2010 earthquake that devastated Haiti—and killed about 316,000 people—had a magnitude of 7.0. Most areas of the world, especially developing nations, aren’t equipped to withstand even small tremors in the earth. It’s those places that are also likely to have fewer seismometers, making the satellite information even more helpful.

As the situation in Nepal moves forward, the aftermath might hopefully speed up plans to make geodetic data available just hours after an earthquake occurs. Satellite systems could be integral in allowing first responders to move swiftly in the face of unpredictable, unpreventable events.

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