Can I feel an earthquake on my boat?

Mind you, with blustery winds and damp, cool conditions, only the most dedicated boaters were likely to have been out on the water at 5.41am when the magnitude 2.4 earthquake struck the bay’s south-east just off Mount Martha on Sunday.

But would anyone out on the water have experienced anything? We put the question to Hugh Glanville, the senior duty scientist at Geoscience Australia, the government department in charge of investigating earthquake activity.

According to Glanville, even if they were right over the top of the Port Phillip Bay earthquake’s epicentre they’re likely to have felt nothing. In contrast, Geoscience Australia received reports from more than 300 people on land who said they had felt the shake.

However, while shallow water – such as Port Phillip Bay – is relatively poor at transmitting the physical shake of the earthquake, anyone in the area of the epicentre could have heard a boom or a noise like a train going past, with water transferring the sound quite well.

“It’s likely that if anyone noticed anything about the earthquake, it would not be felt but it could be heard,” Glanville says.

“Being on the water is similar to when someone is driving a car and there’s a lot of vibration – you really wouldn’t be able to feel anything anyway.

“Most people who report they felt an earthquake are lying down or sitting still, or they can see something shaking to show there’s an earthquake happening."

For anyone on a boat to notice an earthquake, it'd need to be a significant shake, up around a magnitude 4.0 that would cause mild damage or a 5.0 that would cause more widespread damage, Glanville says.

The area around Frankston where the earthquake’s epicentre was located is part of the Selwyn Fault, a fairly new feature in geological terms that Glanville says has been around for anywhere between 1000 and 10,000 years.

The fault runs north-south along the eastern edge of Port Phillip Bay, and has been responsible for a number of small earthquakes in Melbourne’s south-east. Three earthquakes in the last decade have had their epicentre located inside the 2000-square-kilometre bay.

However, because Port Phillip Bay and the nearby Bass Strait are quite shallow, if ever there was a large underwater earthquake it is unlikely to cause a tsunami, Glanville says.

“A tsunami can enter Port Phillip Bay, but because it is so shallow it will not generate a large wave once it is inside,” he says. “If one does it’s more likely to cause localised damage as the waves bounce around inside it.”

Thanks to the protection offered by Tasmania, the bay is also well protected from the types of ’quakes that generate tsunamis, which are usually the result of tectonic platessuch as those around new Zealand that are deep in the ocean and slide against each other with enough force to generate a large wave.

On a final note, Glanville warns boaters to stay off the water if ever there is a warning issued for even a small tsunami.

“Even if it is not a wave that’s visible to the eye, these smaller tsunamis can make big changes to tides and currents. You’re better off to stay right away from the water.”

Likewise, anyone on shore should not hang around on the beach waiting for even a small tsunami to hit.

“You should get to higher ground,” he says. “Even if it is a small tsunami, a car will float in 30cm of water – stay well away from the water.”