‘Stormquakes’ are nothing to fear: scientists

‘‘Stormquakes’’ all around Earth are generating continuous seismic noise in New Zealand, scientists say.

Seafloor shaking caused by storms can rumble like a magnitude 3.5 earthquake and can last for days, according to a US study in which the scientists have coined the term ‘‘stormquakes’’.

GNS science seismologist Dr Stephen Bannister said New Zealand scientists have been aware of ‘‘seismic background noise’’ generated by energetic storms for decades. ‘‘In New Zealand we have weeks that are much ‘noisier’ than others and that is directly related to the occurrence of incoming storms,’’ Bannister said.

‘‘If we dug really deep in to the data, we could potentially see connections to micro earthquakes.’’

Storms are triggering giant waves in the sea, which cause another wave. The secondary waves interact with the seafloor and cause shaking.

The increasing climate means the storms, and the shaking, could become more frequent.

However, the scientists behind the US study said the stormquakes are more an oddity than something dangerous.

Bannister said the research was interesting, but didn’t represent a significant hazard.

The country’s constant seismic noise was a feature of being a small island nation with a large coastline, and exposure to oceanic storms, he said. The national network of seismic instruments, operated by GeoNet, continuously records the seismic background noise from incoming storms.

‘‘This is where ocean wave energy converts to seismic surface wave energy as it hits the edge of the continental shelf and coastline around New Zealand.’’

Bannister said GNS Science has been involved in studies with Victoria University to dissect New Zealand’s’ seismic noise.

Their work focused on seismic tomography – ‘‘imaging’’ the

Earth’s crust with seismic waves produced by earthquakes, he said.

University of Auckland physics associate professor Dr Kasper van Wijk said the magnitude of the shaking was not going to ‘‘rattle us’’, but could become more frequent. ‘‘From my understanding, we’re going to see more storms, so we’ll see more events like this that we can detect.’’

The research was interesting and could be explored more in New Zealand, van Wijk said.

The research posed an opportunity to use the shaking to find out more about the Earth and its structure, he said.

‘‘Signals like this could potentially provide more information. It could be more information about what the earth looks like, what rocks look like and the structure underneath.’’

‘‘In New Zealand we have weeks that are much ‘noisier’ than others and that is directly related to the occurrence of incoming storms.’’ GNS science seismologist Dr Stephen Bannister