How does an earthquake warning system work?

The earthquake early warning system has been deployed in only a few areas as "hot spots" for seismic activity in the world, giving a warning just minutes before the disaster.

Learn about the operation of an earthquake warning system

Mexico, Japan and the US are the countries with this system, the most advanced being ShakeAlert is located in California. It consists of seismic measuring stations that can detect P waves - nondestructive waves generated by earthquakes, which travel through the Earth's crust faster than S waves (the type that creates ground vibrations).

Seismic attacks in Nepal hom0 25/4 caused a lot of human and property damage.(Photo: NY Times)

When the P wave reaches the seismic measurement station, the information is transmitted via telephone lines, modem ports or satellites to the laboratory . Here, the computer will deploy algorithms to calculate earthquake origin and intensity. According to Reuters, ShakeAlert has issued a 5-10 second warning for the San Francisco Bay Area during the 2014 Napa earthquake.

The area around Kathmandu was affected by a massive earthquake in 1934 and 1988. At a meeting in the Nepalese capital earlier this month, disaster disaster experts predicted the next case would occur in several ten years from now.

" If Nepal has a seismic network, acting like a northern California system in the incident last year, people in Kathmandu could get a 15-20 second warning, enough for them to hide under the table or even escape the the building is collapsing, " said seismic expert Peggy Hellweg of the University of California.

According to calculations by the US Geological Survey (USGS), the investment cost of an early warning system for the entire western coastal region of this country is 38.3 million USD , while the cost of maintaining and operating costs about $ 16.1 million.

In 2012, San Francisco's fast transportation system BART was connected to ShakeAlert. A signal from the warning system automatically reduces the speed of the ships before a magnitude 4 or 5 earthquake occurs, reducing the risk of derailment. However, this system is not perfect. If the epicenter is actually in San Francisco Bay, BART will not receive a warning, P waves and S waves will come almost simultaneously.

Japan's warning system, operated by the country's meteorological agency since 2007 , is more general. It has the function of sending alerts to computers, management agencies in the city when an earthquake has great power to break the walls. Ships, nuclear reactors and plants are connected to the system and automatically deactivated when the Tohoku earthquake occurred in 2011, accompanied by tsunamis and consequently the disaster of Fukushima nuclear power plant.

Policymakers at least once reacted harshly to the limited vision of seismic experts. In 2012, the Italian court concluded that six manslaughter investigators could not predict and warn people about the 2009 L'Aquila earthquake, killing 300 people.