EarthScope is using GPS as an Earthquake Early Warning System

When a large earthquake occurs, a warning of seconds to minutes can make a big difference. That warning may give you enough time to move to a safer place, for trains and elevators to be stopped, and for industrial machines to be shut off. In Japan, when an earthquake occurs, people receive text messages on their cell phones warning them of coming earthquake waves.
This movie shows a simulated magnitude 7.8 earthquake on the southern San Andreas Fault in California. The different colors show how fast the ground is moving due to the passing earthquake waves. Notice how long it takes the waves to reach the different cities along the fault.
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Question 1:
How could someone be helped by an earthquake early warning system?
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Question 2:
Which is better to give earthquake early warnings: seismometers or GPS?
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Question 3:
What should I do during an earthquake?
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