Video | Business Headlines | Internet | Science | Scientific Ethics | Technology | Search

 


Deep Alpine Fault sensitive to nearby earthquakes

MEDIA RELEASE

25 August 2014

___________________________________________________________

Deep Alpine Fault sensitive to nearby earthquakes

Victoria University of Wellington researchers have discovered that seismic waves produced by earthquakes happening several hundred kilometres away trigger activity deep beneath the Alpine Fault.

Using a network of seismic recorders called the Southern Alps Microearthquake Borehole Array (SAMBA), set up during a 2009 study, PhD student Calum Chamberlain is exploring the range of seismicity occurring in the central section of the Alpine Fault.

Calum is researching under the supervision of Associate Professor John Townend and Professor Tim Stern from the School of Geography, Environment and Earth Sciences and in collaboration with Dr David Shelly of the United States Geological Survey. This work was recently published online by the journalGeochemistry, Geophysics, Geosystems (G-Cubed).

The Alpine Fault runs along the western side of the Southern Alps and forms the boundary between the Pacific tectonic plate (to the east) and the Australian plate (to the west). Calum’s PhD research involves regular helicopter trips into the Southern Alps to download data and make sure the seismic recorders are operating reliably.

“The Alpine Fault is known from geological measurements to produce large earthquakes every few hundred years, most recently in 1717 AD, but this research is focussed on much, much smaller earthquakes happening almost every day. We are investigating how the fault is being loaded towards an eventual large earthquake,” says Dr Townend.

“Our group has recently detected very small earthquakes—smaller than magnitude one—occurring at depths of 15 to 40 km near the Alpine Fault. These earthquakes have distinctive low-frequency characteristics that enable them to be detected and monitored despite their small size, and provide one of the few signs we have of present-day faulting activity deep inside the plate boundary.”

Analysing three years of data, Calum has found that low-frequency earthquakes happen almost continuously near the Alpine Fault southwest of Aoraki Mt Cook. In addition, when a large earthquake happens elsewhere in the South Island, such as the Dusky Sound earthquake of 2009 in Fiordland or the 2010 and 2011 Canterbury sequence of earthquakes, there’s a sharp spike in the production of low-frequency earthquakes.

One example is the magnitude 6 earthquake near Christchurch in June 2011 that triggered many low-frequency earthquakes on the Alpine Fault over the course of several days. “The Alpine Fault responds to earthquakes hundreds of kilometres away, showing that it’s very sensitive to the small stresses associated with seismic waves,” says Calum.

The next stage of Calum’s study is focussed on understanding the conditions beneath the fault that make it extremely sensitive to weak triggers. This work will also add to knowledge of the fault’s structure at depth.

“Documenting how often these low-frequency earthquakes occur and how they’re triggered by very small perturbations in stress is important for determining how the Alpine Fault is loaded by tectonic processes and better understanding the hazard it poses,” says Dr Townend.

The research is funded by the Marsden Fund of the Royal Society of New Zealand and Victoria University of Wellington, and viewable online athttp://doi.wiley.com/10.1002/2014GC005436


© Scoop Media

 
 
 
 
 
Business Headlines | Sci-Tech Headlines

 

Must Sell 20 Petrol Stations: Z Cleared To Buy Caltex Assets

Z Energy is allowed to buy the Caltex and Challenge! petrol station chains but must sell 19 of its retail sites and one truck-stop, the Commerce Commission has ruled in a split decision that acknowledges possible retail price coordination between fuel retailers occurs in some regions. More>>

ALSO:

Huntly: Genesis Extends Life Of Coal-Fuelled Power Station To 2022

Genesis Energy will keep its two coal and gas-fired units at Huntly Power Station operating until 2022, having previously said they'd be closed by 2018, after wringing a high price from other electricity generators who wanted to keep them as back-up. More>>

ALSO:

Dammed If You Do: Ruataniwha Irrigation Scheme Hits Farmer Uptake Targets

Enough Hawke's Bay farmers have signed up for water from the proposed Ruataniwha Water Storage Scheme for it to go ahead as long as a cornerstone institutional capital investor can be found to back it, its regional council promoter announced. More>>

ALSO:

Reserve Bank: OCR Stays At 2.25%

Reserve Bank governor Graeme Wheeler kept the official cash rate at 2.25 percent, in a decision traders had said could go either way, while predicting inflation will pick up as the slump in oil prices washes out of the data and capacity pressures start to build in the economy. More>>

ALSO:

Export Values Down: NZ Posts Biggest Annual Trade Deficit In 7 Years

New Zealand has recorded its biggest annual trade deficit since April 2009, reflecting weaker prices of agricultural commodities such as dairy products, beef and lamb, and increased imports of vehicles and machinery. More>>

ALSO:

Currency Events: NZ's New $5 Note Wins International Banknote Award

New Zealand’s new Brighter Money $5 note has been named Banknote of the Year in a prestigious international competition. The $5 note was awarded the IBNS Banknote of the Year title at the International Bank Note Society’s annual meeting. More>>

ALSO:

Get More From Scoop

 
 
 
 
 
 
 
 
 
Sci-Tech
Search Scoop  
 
 
Powered by Vodafone
NZ independent news