'Massive jolt and shaking': 4.9 earthquake in Hawke's Bay

The quake struck the Central Hawke's Bay.

A strong shake has been felt across Hawke's Bay this afternoon.

A 4.9 magnitude earthquake struck 5km north of Waipukurau in Central Hawke's Bay.

The quake was described as moderate by Geonet.

It occurred at 4.54pm at a depth of 36km.

Locals reported the quake felt stronger than just a moderate shake.

Omg! Massive jolt and shaking here in Marewa Napier. Gave me a heck of a fright. #eqnz geo net says moderate?

— The Hanan (@Thebighanan) September 4, 2021

"Wowza that was a shake," Andrew Biggs tweeted.

"And that will be quite enough of that thanks Mother Nature," added Andrene Low.

Mum just laughed and told me it’ll be fine 😩

I broke a nail gripping the sofa 😞😞😞 #eqnz

— NinjaKitty - 0.5 Vaxxed🥷🐈‍⬛🇯🇵🇳🇿💮 (@JackyNinjakitty) September 4, 2021

Several Hawke's Bay residents with Android devices also received a Google mobile phone alert about the earthquake.

Napier woman Meg Affleck was watching television at home when she got the Android alert "just a second before it hit".

She said it was the biggest earthquake she'd felt in a long time and it had left her feeling "quite uneasy".

"It's not often I run for cover but for this one I did."

The system had previously been used to alert Android users following a 5.1 magnitude earthquake in August.

The quake was described as moderate by Geonet - but was widely felt. Map / Geonet

Napier woman Selina Hargreaves was standing outside talking to her daughter when she felt a "big jolt".

"It was big enough that I had to steady myself."

Her daughter who was inside said it lasted for around 10-15 seconds.

It was one of the "sharpest and biggest" quakes she had felt but not the longest, Hagreaves said.

Wendy Webster in Waipawa felt a "loud rumble" followed by a "big jolt".

"It pushed me sideways my granddaughter, who was sitting on edge of bed, heard it coming.

"The big jolt pushed her over sideways on her bed."

Napier resident Craig Cooper was on the second storey of his Hospital Hill home when the earthquake began.

He says it was the strongest quake he had felt in the past three years.

"It was a little scary - they don't usually rumble our house like that, it shook slowly but powerfully.

"I looked at my wife and said 'quake'. She was standing up, I was sitting - we both felt it."

The quake was "strongly felt" at Parkhill Stables in Mangatarata Rd in Waipukurau, Shani Hughes said.

"Initially we heard a loud noise and thought maybe a tree limb had come down on the house.

"Then the jolts started and seemed to go on for a while.

"We thought it must've been reasonably close as it was quite noisy."

She said the horses appeared fine afterwards.

"It's approaching foaling time for us and we've had a mare foal early due to the stress of an earthquake once so I always like to go and check."

Nicola Giddens in Dannevirke heard the rumble which "sounded like a truck going past".

"I knew it wasn't, then had a bit of a wobble.

"I don't usually hear them like that. It was definitely a different noise."

'A second before quake hit' - How the alert went to phones so quickly

The alerts in this afternoon's quake were sent out to Android phone users as part of the Android Earthquake Alerts System, a trial launched in NZ and in Greece earlier this year.

It uses a physics-based approach to determine the earthquake magnitude and location.

Accelerometers built into most Android smartphones are used to detect seismic waves which indicate a potential earthquake with this signal sent to Google's earthquake detection server, along with a coarse location of where the shaking occurred.

The server then takes this information from many phones to figure out if an earthquake is happening, where it is and what its magnitude is.

Alerts are only issued for earthquakes estimated be a 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.