By Rong-Gong Lin II -
A prototype earthquake early-warning system worked again Friday night, giving seismologists in Pasadena about a four-second heads-up before shaking was felt from the magnitude 5.1 quake that struck near La Habra.
The system is being tested by a team of scientists on a U.S. Geological Survey project to create a statewide network.
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Seismologists believe they can create a system to give 40+ second earthquake warning
