Summary: 74 Scientific American, April 2011 Illustration by Tom Whalen
Earthquake early-warning networks
detect the earliest stages of an earth-
ple of the danger. The alerts can pro-
vide tens of seconds of warning time.
Most systems rely on the fact that an
earthquake comes in two parts: a fast-
moving, sudden jolt and a slower-mov-
ing wave that causes the great majority
of the damage.
Anetwork of seismometers can quick-
ly identify the earthquake's epicenter,
improve predictionsofthe earthquake's
magnitude and reduce the incidence of
ber of countries around the world. A
proposed system for California would