What would a safety engineer do with an extra 20-seconds?

My review of "Second Before the Big One" by Richard Allen in the April 2011 issue of Scientific American.

We have all witnessed the power and destruction of an earthquake over the last several weeks. The recent events in Japan demonstrate the challenges safety professionals face with natural disasters. Earthquakes, unlike tornadoes, hurricanes, or other extreme weather events, historically have not provided the time and means for public warnings. Some areas, Japan is one, have early warning systems. Our most earthquake prone region in the United States, California, does not have an earthquake early warning system. California is one of the most earthquake-prone places on earth, yet it lacks even a basic warning system. A partnership of universities and state and federal agencies has proposed expanding the seismic network to cover the state. The program would cost $80 million (see California Integrated Seismic Network - - www.cisn.org).


The science and technology behind an early warning system is rather straightforward. Earthquake early warning networks and systems detect states of an earthquake and sound an alarm to warn people, companies, and government agencies of danger. Most systems rely on the fact than an earthquake comes in two parts. All earthquakes are made of two types of waves. The P-wave compresses the earth as is moves, like a sound wave but does not cause much damage. The S-wave that follows deforms rock up and down like an ocean wave. It delivers most of the tremor’s violent energy.

A network of sensitive seismometers would provide the basis for wave detection to warnings. A single seismometer can estimate the magnitude of an earthquake based on the wave science. Any P-wave with a high amplitude and low frequency would trigger a warning. False and missed alarms would be minimized with networks - - an average estimate of the magnitude would be utilized. This proposed network would provide safety professionals with maybe 20-seconds of warning. For example, an earthquake centered in the Santa Cruz Mountains would have a 30 second travel time to make the 60 miles to central San Francisco.

What would a safety engineer do with extra 20-seconds when facing the prospects of a devastating earthquake? The author outlined the following examples of what could be done:

• Commuter rail systems would automatically brake reducing the chance of derailments.

• Manufacturing plants would stop operations and switch equipment into safe mode.

• Construction sites would alert workers to move out of the most dangerous locations.

• Mobile phones and personal computers would light up with personalized alerts.

• Airplanes on approach to area airports would be given last minute “go-around” signals.

• Schools would sound an audible alarm, giving students time to get under their desks.

• Elevators in high-rise buildings would stop at the nearest floor and open their doors.