Quake Alarms May Buy Time --in Some Cases

Mexico City has had an early warning system for earthquakes for six years, giving about a minute’s notice on radio stations that a big quake has begun in the Pacific subduction zone 200 miles away and will soon be shaking residents of the Mexican capital.

A minute may not be long, but for those hearing the warning, there is time to put glasses or shoes on, retrieve a flashlight if it’s dark, and dive for safe cover. For a business or utility, there may be time to shut down vital systems.

Such a government-coordinated general warning system in Los Angeles for big quakes on the San Andreas fault and elsewhere remains at least five years away. And that deadline seems to be receding. It has not changed in the last year and a half.

But at least two private warning systems are being marketed locally which can provide a home, a school or a manufacturing plant with at least some warning that primary quake waves arriving in the city will soon be followed by much stronger secondary waves.

Of course, for any warning system to work, the quake has to be at least 50 miles away. There could have been no timely warning within Los Angeles of the Northridge earthquake.

Two months ago, EQ Technologies Inc. of Sherman Oaks began selling through Home Base stores an Israeli product called EarthQuake Alert. It looks a bit like a smoke detector and sounds an alarm in a home when a microprocessor inside detects P (primary) waves.

The price of the device, powered by four AA batteries, is about $100, and the firm is seeking additional sales outlets.

Another company, Earthquake Safety Systems of Ventura, is marketing a more elaborate device for $8,000. It is being sold through various dealers to large institutions only, such as schools and industrial plants. Its warning sounds through public address systems and it uses regular power supplies with a battery backup if the power goes down.

Scientists at Caltech and the U.S. Geological Survey point out that neither product can convey quite as early a warning as the Mexican system because they detect the P waves only when they arrive at the sites of the individual devices.

The Mexican system, by contrast, uses sensors that detect the waves at their points of origin, and through electronic connections immediately interrupts broadcasts in Mexico City.

Over a 200-mile distance, the Mexican system may convey a warning about 30 seconds faster than the systems being marketed in Los Angeles, according to Egill Hauksson, a Caltech seismologist.

Also, Hauksson said, “If the S [secondary] wave is going to be very damaging, the P wave would be strong enough to be felt all over the place anyway. You wouldn’t need a detector to tell that a major earthquake was happening.”

Still, Hauksson acknowledged that the devices for sale in Los Angeles “might give people a little bit of a leg up.” Added his Caltech colleague Thomas H. Heaton, “Any additional information you get on an earthquake may be useful.”

One reason, as pointed out by Nachum Inlender, manager of EQ Technologies, is that many times when an earthquake is just beginning, people don’t realize what it is. There is a famous film of a movie studio during the 1933 Long Beach earthquake that shows actors confused for crucial seconds before it becomes obvious what is happening.

“We recommend that families become acquainted with our EarthQuake Alert alarm, and then they will know definitely that it is going to be an earthquake,” Inlender said. “Then, they can take precautions right away.”

He said the processor in the device is able to distinguish between a sonic boom, a truck passing by and P waves, so false alarms are avoided.

Andrei Reinhorn, a professor and chairman of the department of civil engineering at the State University of New York at Buffalo, tested the $100 device for homes and found it reliable.

But Reinhorn warned in an interview that the device might not function if a house is on bedrock. “It depends very much on soil conditions,” he said.

The device contains a warning on its cover: “All users and homeowners are advised that, even when working properly, the EarthQuake Alert may fail to signal a destructive earthquake if the user is located at the epicenter of the quake, the geological foundation below the home fails to transmit to the system the proper preliminary temblor waves or if there are other obstacles to the . . . system sensing the necessary preliminary waves.”

Still, Inlender said, “The Mexican system is not available in the United States. . . . Consumers cannot wait. Right now, we have an instrument that can help, and it’s available.”

While the EarthQuake Alert alarm is customarily attached to a bedroom wall, the more elaborate and expensive Earthquake Safety Systems device is directly attached to the ground.

Owen Widdicombe, an officer of that firm, said that fewer than 100 of its devices have been sold to schools, but hundreds have been sold to industrial firms.

“The schools often don’t have the money,” he said. “We have only one in the Los Angeles Unified School District, at Jefferson High School.”

During the Northridge earthquake, the system did perform as designed at Colton and Apple Valley schools, Widdicombe said, but because that quake occurred at 4:31 a.m., there were no students on hand.