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New seismometer network fills knowledge gap

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Waihōpai – A new network of seismometers in Southland will fill a seismic blind-spot to uncover any hidden earthquake fault lines in the deep south.

University of Otago researchers, funded by the Toka Tū Ake Earthquake Commission, has started installing seismometers across 19 Southland sites.

The aim is to capture smaller earthquakes than the existing Geonet network to get a better understanding of seismic activity and hazard in the region.

Historically, EQC thinks Southland is a low seismicity area, but the distance between Geonet sensors is over 100km and a lot of the smaller earthquakes go unrecorded.

These new sensors will be roughly 30km apart, which will give us a much better idea of active fault lines in Southland.

Previous seismic activity is often judged by indicators on the surface where land has been uplifted and broken in past earthquakes, but in Southland those indicators may not always tell the full story.

EQC says there is a lot of scarring in the Central Otago landscape from prehistoric earthquakes because it is dry, but the weather in Southland is very wet, and so the evidence from past earthquakes is removed from the landscape more quickly.

The vast plains of Southland are similar to the Canterbury landscape before the 2010-11 earthquakes.

These regions are similar in that we expect there are active faults concealed beneath these plains, but we cannot necessarily identify them from looking at the landscape alone.

EQC funds about $20 million in natural hazard research each year to help communities, councils and decision makers to be better prepared.

Similar seismic deployments have greatly improved the understanding of the location and frequency of earthquakes in surrounding regions such as Fiordland and Central Otago, but there is a significant knowledge gap about the upper crust fault lines and seismicity in Southland.

The region also lies at the junction of multiple geological terranes of contrasting materials that may influence where earthquakes occur.

The team of researchers will be working closely with a variety of landowners who have agreed to install the sensors on their land.

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