6.7 quake risk
New fault in our backyard
A newly discovered fault line near Morrinsville could potentially produce a 6.7-magnitude earthquake.
This is comparable to Christchurch’s 2010 Darfield earthquake.
GNS Science located a 25km fault line in Te Puninga, 27km from Hamilton, and is working to determine how great the earthquake risk is to surrounding residents.
Based on its length of 25km, the fault could generate a 6.7 magnitude earthquake, earthquake geologist at GNS Science Dr Pilar Villamor said yesterday.
‘‘If it ruptured, Morrinsville would potentially experience the same level of shaking Christchurch had during the 2010 Darfield quake,’’ she said.
‘‘And it would be relatively strong in Hamilton as well.’’
The area, which is traditionally safe from quakes, allows the Earthquake Commission to understand the risk of future earthquakes in the area and how to prepare for the risk.
‘‘Some of the changes are seldom, and an earthquake might not happen in our lifetimes.
‘‘But it’s more about being aware of the fault and planning for it,’’ Villamor told Stuff.
Areas closer to the fault line will experience stronger shakes and possibly some liquefaction, but the region won’t ‘‘suffer more shaking just because we know about it’’.
Two large trenches were dug on the Te Puninga dairy farm on Monday, 3km from Morrinsville, after high-resolution satellite data that looks through vegetation noticed a ridge going through the farm.
The trenches expose soil layers displaced by previous earthquakes over the past 20,000 years and samples are taken from each layer.
The samples are dated by experts at the University of Waikato and in Spain.
‘‘This will tell us how often the fault has ruptured, and the magnitude of the quakes it has produced,’’ Villamor said.
‘‘That information in turn will help us to understand the risk of future earthquakes in the area and how to prepare for that risk.’’ Researchers mark each fault line using colourful tabs.
The fault line is connected in depth, but as it gets closer to the surface it’s broken up when a rupture occurs.
The Earthquake Commission invests $17 million each year in scientific research and data to reduce the impact of natural hazards on people and property.
The project, along with others around the country, allows researchers to get a better idea of the areas otherwise deemed as safe from earthquakes, that are actually at risk.
EQC chief scientist Jo Horrocks said fault lines are all over New Zealand.
‘‘We know where all the big ones are, but these little ones can be all over the place,’’ Horrocks said.
‘‘Even though these low hazard faults don’t go off very often, it doesn’t mean they can’t ever go off.
‘‘The people of Hamilton are not facing any greater risk than they were yesterday.
‘‘It may be concerning to people, but more knowledge is always a better thing.’’
Field work will be complete within a week, but the project is expected to last until the end of the year.
Local iwi Nga¯ti Ha¯ua and Nga¯ti Hako, the Waikato Regional Council and local land owners are in support of the project.