New Zealanders keen for an earthquake early warning system
29 August 2019
New Zealanders have welcomed the idea of an early warning system for earthquakes so they can be mentally prepared, as well as drop, cover and hold in the moments before major shaking occurs.
An EQC-funded project led by Dr Julia Becker from the Joint Centre for Disaster Research at Massey University and GNS Science has surveyed how Kiwis would use an early warning system that could give a few seconds or up to two minutes warning before they felt significant earthquake shaking.
Over 3000 New Zealanders responded to the survey with 97% stating that they thought an earthquake early warning would be useful, particularly for taking some sort of action to keep themselves safe, and 81% saying they would drop, cover, hold.
EQC’s head of Resilience Strategy and Research, Dr Jo Horrocks says the research project was extremely valuable to see how New Zealand would benefit from such a huge investment.
“Other countries already have an early warning system but they can be expensive, so it’s important to understand how New Zealanders might use the system before any planning starts,” said Dr Horrocks.
“The survey has already delivered interesting and useful results. I’m looking forward to the full report.”
Dr Becker, who conducted the survey, said that she had run a similar survey in Japan where an earthquake early warning system has been in place since 2007.
“One of the surprising things is that both countries had exactly the same rate of 83% of people saying that an early warning system would help them get mentally prepared for shaking. For people in Japan, this was the greatest value of the system.”
The project team was pleased with the large number of Kiwis responding to the survey and thanked all those for taking part.
Dr Becker says that as well as drop, cover, hold, survey participants also said they would take actions like moving away from dangerous areas or immediately pushing floor buttons to get out of a lift.
One key part of the survey looked at what level of shaking people wanted to be alerted about. “51% wanted to be warned about a moderate Modified Mercalli (MM) shaking intensity of 5, which would most likely wake you up and set some doors swinging or shift small objects,” she said “ while 25% of people surveyed only wanted to be warned if a strong MM6 earthquake where it’s difficult to walk steadily and objects fall from walls and shelves, was about to hit,” she said.
“A risk with an early warning system is that people get alerts for weak shaking and stop paying attention,” said Dr Becker who added that over 80% of people indicated they’d prefer to be warned through their mobile phone.
Dr Becker also spoke to groups of service providers including power, water, rail and hospitals to see how useful they would find an earthquake early warning system.
“We’re now analysing the results of all our research and will be reporting our conclusions and recommendations at the end of this year,” said Dr Becker.
An early warning system uses the two types of waves created by an earthquake with the P-wave arriving before the actual shaking starts.
The P-waves travel very fast and are picked up by the seismographs almost immediately to compute the earthquake location and size and rapidly send out expected shaking strength and arrival time. The S-waves that cause the shaking and damage travel more slowly, enabling a warning period of a few seconds and up to two minutes, depending on how close you are to the epicentre.