An eminent U.S. seismologist is urging the installation of a national early warning system to alert people to an impending earthquake.

Richard Allen, director of the University of California, Berkeley's Seismology Laboratory and professor of Earth and planetary sciences, writing a Comment piece in the journal Nature, has taken politicians and public officials to task for not putting an early warning system in place before the next major quake occurs.

Recent decades have seen dramatic improvement in the technology to detect quakes, he said, largely led by Japan, as proven by the advance warning people there received about the deadly earthquake that struck in 2011.

With the advance notice trains were stopped, chemical plants shut down and people were able to take cover, Allen said.

While California, Oregon and Washington have initiated programs to create early warning systems for parts of their areas, that's not enough, Allen wrote; there should be an expansion of such systems to cover the entire United States, particularly areas most at risk.

It's not a matter of whether a major quake will strike, it's when, Allen said, and if people have prior warning -- the amount of which would depend on how far they are from the epicenter -- then lives could be saved and property damage minimized.