Tens of thousands of us Hamiltonians were jolted awake at the exact same moment this morning, as pressure that had been slowly building beneath the central North Island was suddenly released, sending a ripple of shaking across the country.

Not many of us are usually up at 4:51am on a Saturday, but the magnitude 5.9 earthquake, which struck close to the Earth’s surface near Taumarunui, west of Taupō, rattled homes across Hamilton.

We felt the consequences of the ground beneath this part of New Zealand slowly being stretched. As it stretches, cracks in the Earth's crust - called faults - can suddenly slip, releasing energy as an earthquake.

This is completely normal around the Taupō Volcanic Zone, where one of the Earth's tectonic plates is slowly sliding beneath another, putting the crust under constant tension.

Think of it like slowly breaking apart a block of chocolate. It bends at first, but eventually it snaps. That sudden snap is what happened deep beneath us this morning.

Pets and residents of Hamilton Zoo were among the first to sense the rumbles this morning. In Fairfield, Kush says it was Chicken the cockatiel who felt it first.

Hamiltonians living near the Zoo say some of the animals sounded confused. The Siamang Gibbons reportedly started singing during the shake.

Laura, from Nawton, says her dogs reacted before she realised what was happening.

Tom in Rotokauri received an emergency alert on his phone, got out of bed and noticed the hanging lights swinging and his pool water sloshing back and forth.

Seconds before the shaking began, many Android users across Hamilton received a loud earthquake warning. Some say the alert was more startling than the shaking itself.

The warning system works by using tiny motion sensors built into Android phones. When thousands of nearby phones detect the first vibrations of an earthquake, they automatically alert Google's servers, which quickly send alerts to people further away. Smart.

Those closest to the epicentre usually get little or no warning because the shaking reaches them almost immediately. But people further away, like many in Hamilton this morning, can get a few seconds' notice. iPhones don’t have this feature, sorry..

At Waikato Hospital, the shaking was particularly noticeable on the upper floors. Jeanette says her brother, on the eighth floor, felt the building sway.

Kelly, on Level 5, was feeding her baby when "the door swung open, the walls were swaying and making a creaking sound. It went on for about a minute."

Neil in Chartwell says his house was creaking and swaying for about 15 seconds after it woke him up. Ta Li in Frankton got a fright, like many other Hamiltonians.

Visitors felt it too. Isabella, staying at the Novotel in Hamilton's CBD, says the shaking woke her from sleep.

Hamilton has a pretty good reputation when it comes to natural hazards. Earlier this year, scientists ranked us as the major city with the lowest overall natural hazard risk in New Zealand.

Most earthquakes felt in Hamilton happen somewhere else - like the one this morning. Even when an earthquake is a long way away, the shaking can travel hundreds of kilometres through the ground.

Paul from Claudelands still remembers feeling the 2016 Kaikōura earthquake from his home in Hamilton.

But scientists have actually discovered several active fault lines beneath Hamilton, many of them found during the construction of the Waikato Expressway.

Research from the University of Waikato shows these faults are capable of producing moderate to large earthquakes - but they rupture very rarely.

Based on what researchers know today, Hamilton experiences strong earthquakes, on average, about once every 3,000 years. The local faults have produced several large earthquakes over the past 15,700 years.

While earthquakes that start in the Waikato are uncommon, we have experienced several notable events fairly recently, including magnitude 6.2 earthquakes in 1891 and 1921, and a magnitude 6.3 earthquake in 2012.

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