Google alert confusion rattles Bay residents
Shaking of cellphones generated warning
It wasn’t just the 5.1 magnitude earthquake that woke residents across Hawke’s Bay on Monday morning. Many bleary-eyed Android users were also left in a state of confusion after receiving a Google mobile alert which described it as an estimated 6.0 magnitude quake off the coast.
The inaccurate alert, generated by Google detecting widespread shaking of cellphones across the region, had some wondering whether they needed to head to higher ground.
Government-funded alerts system GeoNet reported the quake was centred about 10km southeast of Tokoroa in the Waikato region and struck at a depth of 160km shortly after 1am.
It was widely felt, particularly in the North Island, with almost 2800 people recording their responses on the GeoNet website. A social media post by GeoNet explained deep earthquakes, such as this one, were typically widely felt, but not usually close to the centre.
Residents across Hawke’s Bay took to social media after being confused by the alert issued by Google, which described the quake as a 6.0 magnitude quake and put the epicentre off the east coast.
Hastings-based Jill Fallowfield said she was woken by her cat meowing in her face.
“I’m guessing she could feel it coming so I got up to see what was up with her and felt the jolt.
“A few minutes later I got the Android emergency message that said it was out at sea so looked at GeoNet, who said Tokoroa.”
It was confusing and left her wondering whether there had been two separate quakes.
Others said they had been surprised by the alert. Many said they did not know about the system.
One woman said she heard the quake and felt her house creak but did not receive the alert and was “gutted” not to get it. Others were relieved not to have received it.
What is Google doing?
The alerts went to Android phone users as part of the Android Earthquake Alerts System, a trial launched here and in Greece this year. It uses a physics-based approach to
determine magnitude and location.
Accelerometers built into most Android smartphones detect seismic waves, which indicate a potential quake, with this signal sent to Google’s earthquake detection server, along with a rough location. The server takes this information from many phones to see if a quake is happening, where it is and its magnitude.
Alerts are only issued for quakes estimated be magnitude 4.5 or larger and are different from the National Emergency Management Agency system used to alert mobile phone users about Covid-19 lockdowns, as well as tsunamis and earthquakes.
Google comment has been sought.
Geonet not immediately right either
John Ristau, a GNS Science seismologist, explained earthquakes measured by GeoNet go through a
series of automatic and preliminary solutions.
“In this case the first automatic solution was magnitude 3.4, which was reviewed, based on additional data, to magnitude 5.1.
“Having an initial magnitude lower than the final magnitude is not uncommon for deep earthquakes.
“Nearby stations typically underestimate the magnitude of deep earthquakes, sometimes by quite a bit, and we have to wait for data from further away stations to get a proper magnitude.”
On the Google alert confusion, Ristau said he welcomed any innovation that helped build the country’s resilience to earthquakes, which complemented the crucial work done by GNS Science and GeoNet.
The National Emergency Management Agency is the official agency for providing advisories and warnings.
A spokesman for the agency said they had not been involved in the development of the Google earthquake early warning system, but it was intended to provide people with a few seconds heads up that earthquake shaking may be imminent.
This helped people “mentally prepare” and take immediate life-safety actions such as drop, cover and hold, before seeking further information from official channels.
He said GeoNet continued to be “the definitive source” of earthquake information for New Zealand.
“We encourage everyone to download their app as it is an easy and fast way to check the details of all earthquakes located in and around New Zealand.”
National advisories and warnings, when there is a serious threat, are published on its website civildefence. govt.nz, and Twitter @nzcivildefence.