Scientists have discovered seismic warning signals that can precede an earthquake.

It isn't yet clear whether the new insights, gained from studying a large fault in Alaska, can help alert us to any coming quakes here.

But the observation has raised the possibility that real-time monitoring of similar precursory signals from large faults could one day be used as a tool for forecasting damaging earthquakes.

The research team, which included seismologist Yoshi Kaneko of GNS Science, studied a number of earthquakes on the 180km-long Minto Flats Fault Zone in central Alaska.


They found that two quakes some years apart, of magnitude 3.7 and 3.8, were preceded by a "nucleation process" characterised by a radiation of high- and low-frequency waves lasting about 20 seconds.

The process, which was predicted only by computer models and laboratory analogue experiments at this stage, involved numerous smaller earthquakes and a very-low-frequency earthquake occurring at about 19km deep that transitioned into a normal earthquake.

The generally accepted view was that earthquakes start abruptly, with no evidence of a precursory process.

But the Alaskan research had shown there were complex processes at play deep within the seismogenic zone of some large faults.

Kaneko said the study benefitted from a temporary deployment of earthquake-recording instruments in the region that was not well-monitored previously.

The instruments enabled precise measurement of timing, depth and location of the precursory signals that led up to the earthquakes.

To explain the nucleation process, the study proposed a computer model in which slow slip on a fault transitions to fast slip that results in a normal earthquake.

Kaneko said more work would be needed to confirm the validity of the computer model of the Alaskan nucleation process.


"Research from around the world suggests these type of precursory signals are very rare," he said.

"We haven't rigorously searched for this type of signal in New Zealand yet, but we plan to do this in the future."

It wasn't known if faults in New Zealand would show the same kind of precursory activity as the Alaskan fault.

"As of now, we know that most earthquakes start abruptly, without any nucleation signals," Kaneko said.

"This fact makes it very difficult to predict earthquakes."

The research, just published in major scientific journal Nature Geoscience, was part of an international collaboration and partly supported by Royal Society Te Apārangi's Rutherford Discovery Fellowship.

It comes after a multi-nation project of the East Coast of the North Island to install a new sub-seafloor earthquake observatory.

The new listening post, established amid New Zealand's high-risk Hikurangi Subduction Zone, focuses on "slow slip" earthquakes, which have been implicated in several large-scale events around the world.