Tuesday, 5 April 2011

When is the BIG ONE?

The only earthquake to cause significant damage in Dunedin occurred on April 9, 1974. I remember it clearly actually, even though I was only 4 years old. I was standing in the living room looking out window, the floor was rolling and I was really scared.
The quake was estimated to be 12km deep and centred 10km south of the city. (see ODT articl)
So a major faultline runs pretty much right underneath our house in Waldronville.

Taieri fault lines need research

Otago Daily Times By Eileen Goodwin on Tue, 7 Sep 2010
Research was ongoing, but it was now speculated Dunedin's 1974 earthquake was caused by the Green Island fault, rather than the Akatore fault, whichhad not been active for 1000 years, and 2000 before then. read more here

Quaking in our boots: How prepared is Dunedin?

Otago Daily Times By ohno and Kim Dungey on Sat, 18 Sep 2010

If earthquakes were as regular as clockwork, then a "big one" of magnitude 8 affecting Otago is 43 years overdue. "There is a 50% chance over the next 50 years that there will be a magnitude 8 earthquake on the alpine fault. read more here
Some facts that we should all be aware of. (source)

• The New Zealand Alpine Fault is one of the world’s most prominent and active fault lines
• The East Coast of the South Island is part of one of the earth’s tectonic plates
• The West Coast of the South Island is part of another plate
• The Southern Alps have grown 20,000 metres over the last 25 million years, but have eroded most of this growth away
• Much of the erosion of the high country ends up on the beaches of our coasts
• The Alpine Fault is due to move in a major way
• All of the above will impact upon us, or our children, and how will we continue to live in the “shaky isles”.

"The New Zealand Alpine fault which stretches 650km from Fiordland to North Westland, is known to have been the host of five events of about Force 8 magnitude where the effects have either been observed or can be measured geologically. The dates that can be provided for past events are circa 1350, 1475, 1615, 1725 and 1826. Using these dates, published in the recent “Hostile Shores” by Dr Bruce McFadgen, the interval between major movements coming forward in time, has been 125 years, 140 years, 110 years, and 101 years. The average gap between major movements over these 660 years has been 119 years. Using this average, another major Alpine Fault movement could have been anticipated in 1945. In other words, we are overdue by some 65 years, although if the longest gap of 140 years is used, we are overdue by only 44 years."

It is generally agreed between geologists from all round New Zealand that a Force 8 event would result in an 8 metre horizontal displacement and a 4 metre vertical displacement along the fault.

So with all this earthquake talk, I came across an interesting video on youtube on the "Expanding Earth" theory. Kind of blows the whole tectonic plate theory out the window.


Anonymous said...

And who is prepared for it? hardly anyone.


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