How other countries warn people a disaster is on its way
The new Civil Defence alert system tested last week was an insight into how technology can warn Kiwis out of harm’s way.
The Ministry of Civil Defence and Emergency Management (MCDEM) reported the signal was successfully broadcast from the top of the North Island to the bottom of the South Island.
However, it estimated only a third of the mobile phones in the country would have received the test alert – about 2 million phones.
“[It’s] very encouraging,” said communications manager Anthony Frith. “The main issues that have surfaced are to do with the variability between handsets, so we are collecting information from the public about this.”
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New Zealand’s new system will be used when hazards appear that involve threats to life, health or property, or in some cases for test purposes.
While the Civil Defence say the emergency alerts are not strictly to be used in the event of an earthquake or tsunami, the technology mirrors what is being used in other countries that, like New Zealand, live under the threat of earthquakes.
In September a massive 7.1-magnitude quake ripped through Mexico City toppling more than 40 buildings and killing 370 people, experts believe the death toll could have been far worse if it had not been for its warning system.
WHAT HAPPENS IN OTHER COUNTRIES?
Today the technology exists to detect earthquakes so quickly, that an alert can reach some areas before strong shaking arrives.
Essentially this is done by detecting the first energy to radiate from an earthquake called the P-wave energy, which rarely causes damage. This data allows an estimate of the location and magnitude of the earthquake.
The anticipated ground shaking across an affected region is worked out and a warning is provided to local populations, before the S-wave arrives (they travel about 2 kilometres per second slower than P-waves through rock) which is the strong shaking that usually causes most of the damage.
Mexico’s civil defence network currently provides up to 60 seconds’ warning of earthquakes to Mexico City in the event of an earthquake along the southern coast, and as many as 30 seconds to Oaxaca City if an earthquake occurs near the coast of that state, with shorter times for earthquakes centred closer to the city.
Their sensor network is regarded as the first earthquake early warning system available to the public, and came about after the 1985 Mexico City earthquake – which killed as many as 30,000 people – prompted authorities to have a rethink.
More than 100 sensors off the coast lines and in its mountains, monitor movement and send warning signals to authorities and those who have receivers. More than 90,000 users in Mexico City, including almost all public schools, have receivers.
It costs about 20,500 pesos – around NZ$1600 per device – for the cheapest system and installation. Mexico City also has a system of loudspeakers that give out a warning to the public.
More than 20 million people live in the capital and surrounding area, and shockwaves from earthquakes may arrive at the city much later.
However, following its latest earthquake the Mexican Government’s civil defence – known as C5, for Command, Control Computing, Communications and Contact – announced a new smartphone program to add to its warning capabilities. It is an app that is downloaded for free and sends an alert much like New Zealand’s new system.
Japan uses an earthquake early warning which alerts its national meteorological and hydrological services, as well as the general public.
Japan has 4235 seismometers – a machine which measures the motion of the ground – installed throughout the country, and when two or more detect movement the Japanese Meteorological Agency roughly predict the earthquake’s epicentre and warn people through TV and radio that strong shaking is expected.
It aims to help minimise damage by alerting people to take shelter or move away from dangerous areas such as cliffs. Railways use this warning to slow down trains, and factory workers use it to stop assembly lines before the shaking reaches them.
It was considered to be effective during the 2011 Tohoku earthquake and tsunami which killed more than 10,000 people – authorities believe many more people would have died without warning system.
Japan also operates a mobile alert system, and after 2007 it was mandatory for all cellphones on the market to be able to receive this service.
The US Federal Emergency Management Agency estimates that earthquakes cost the country around US$5.3 billion annually. Almost three quarters of the damage occurs along the West Coast, and 60 per cent in California alone.
The last big one in the US struck Southern California, a 7.8 magnitude quake in 1957.
Their first warning system began transmitting real-time warnings to select users in California in 2012. By 2016 seismometers were installed in the Pacific Ocean, and in April they introduced ShakeAlert – an alert system used along the entire West Coast.
However the country’s early warning system is still at half-capacity, and long term funding needs must be secured before the system can begin sending general public notifications.