November 29, 2023

Discovering new fault lines is becoming more common – GNS scientist

Watch: GNS scientist on the three new fault lines discovered in the Auckland region.

A GNS scientist says it’s becoming more common for new fault lines to be discovered thanks to laser technology. 

It comes after research released in May revealed three active fault lines in Auckland’s Franklin region. 

The active faults identified are the Pukekohe (Waiuku) Fault, the Paerata Fault and the Aka Aka Fault.

GNS Science produced the first detailed geological map of the region in nearly 30 years, which showed these faults for the first time in such detail.

“One of the features which we saw in the landscape there, thanks to having some very detailed technologies… is telltale signs in the landscape of fault movements having broken through to the ground surface in times past in several locations there,” geologist and geomorphologist for GNS Science David Barrell told AM on Thursday. 

These new faults were discovered for the first time thanks to laser radar technology, Barrell said.  

“One of the things which is a major asset in our toolbox these days is Lidar (Light Detection and Ranging), which is produced by laser scanning of the ground from aircraft and it produces an exquisitely detailed picture of the land surface,” he said. 

“In that, we can see steps in the landscape which can only really be explained by the ground having been moved and they’re on the lines of faults that we knew about and they indicate to us that these faults have moved in the geologically recent past.”

Barrell told AM co-host Ryan Bridge it’s not something locals in the area need to be worried about as the research suggests the fault lines have low seismic activity.

“The thing with the Pukekohe area, it’s an extinct volcanic field, the last eruption was about 500,000 years ago and that has sort of formed the foundation of the land surface through there,” he said. 

“It’s a long period of time in which any fault movements that have occurred through that half million years, the expression can still be seen in the landscape, so because we can see them there doesn’t mean that it’s very recent activity… so we’re seeing the cumulative effects of movement over a very long period of time, it doesn’t mean that they’re wildly active.” 

Barrell said it’s becoming increasingly common for new faults to be discovered thanks to the technology they have. 

“We can see details that were never really apparent when all you had beforehand was aerial photographs because the ground is covered in crops and livestock and trees and so the Lidar can see through all of that and we can see features of the land surface that are becoming revealed to us in many places where we hadn’t seen it before,” he explained. 

Watch the full interview with David Barrell in the video above.

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