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NASA's Space Place

Earth-Shaking GPS News

Alex H. Kasprak
National Aeronautics and Space Administration

Early Saint Patrick’s Day morning, residents of Los Angeles woke up to a jolt. The ground was rumbling. Then, suddenly, it seemed as if the whole world was kicked out of place. It was an earthquake.

Within seconds, computers at the United States Geological Survey pinpointed the quake’s center and calculated how strong it was. They figure that out with a network of seismometers—tools that measures how much the ground shakes. But some scientists think that GPS (Global Positioning System) devices can help provide the same information even faster and with greater accuracy.

Getting this information right as soon as possible is important. That’s because the big waves traveling through the ground from an earthquake are slow enough that you can actually warn other areas to prepare for some shaking before the waves get there.

But right now it can be hard to get an accurate estimate right away. Sometimes the strength of a quake or the location of its center is miscalculated at first. The St Patrick’s Day quake, for example, was originally reported as being stronger than it actually was.

And this is where GPS comes into play. That’s right, the very same system that tells you where you are on the Earth and helps you navigate to the nearest pizzeria, may also monitor ground motion caused by earthquakes. Scientists are currently testing such a system. They are taking existing GPS base stations—with extremely accurate GPS receivers—and adding new tools to them so they can sense subtle movements in the ground as they occur.

The GPS base station provides the location down to a few centimeters. The new tools monitor and detect slight movements of the Earth’s crust at the station’s location. With a network of these stations, you may have enough information to estimate the earthquake’s center and its magnitude and then issue a warning automatically and within seconds.

This would not help people right near the center of the earthquake. Yet even a few seconds of warning could be the difference between life and death for people further away. They could prepare by taking cover, shutting down dangerous things like natural gas lines, stop elevators at the nearest floor, and slow down moving trains.

Earthquake monitoring is not easy. Predicting earthquakes remains pretty much impossible. But an early warning issued by a network of extremely accurate GPS stations could be just the tool to help reduce some of the risks of these Earth-shaking natural disasters in the future.

Learn about how GPS works at NASA’s Space Place: and be sure to check out a fun animation and poster about how it can be used to hunt down a tasty pizza:

A GPS antenna outside of Los Angeles, California. Credit: USGS.