Shaky quake appreciation

About earthquakes

There’s been a lot of nonsense in the media over the Canterbury earthquakes and the more recent shakes in Cook Strait off Seddon. Contrary to reports, the “big one” has not yet hit New Zealand. Christchurch did not suffer a 7.1 earthquake in 2010, Darfield did. Christchurch is more than 40km away from Darfield, consequently, the effect on the central city was the equivalent of a quake of significantly less than 7.1.

The more damaging earthquake in February 2011 was magnitude 6.3 and much closer to Christchurch. It was a relatively small shake in the great scheme of things but it nevertheless caused massive structural damage, tragic loss of life, and much subsequent suffering for the people of Christchurch.

When the inevitable big one does hit, it will be far more devastating and it will deal a catastrophic blow to our precarious economy. The economic effects could last for decades.

We will all be victims.

Think about it

Thanks Wikipedia

The late broadcaster Paul Holmes—no stranger to hyperbole and not one to let the facts get in the way of a good story—stated on NewsTalk ZB that it was the “big one” we’d been waiting for. They played his misleading clip over and over several times a day for weeks to reinforce the wrong message.

The Wellington Fault runs smack-bang through the cities of Wellington, Lower Hutt, and Upper Hutt. The inevitable big quake there is yet to come.

It’s not ignorance does so much damage; it’s knowing so darned much that ain’t so. Josh Billings

The first Canterbury earthquake was far smaller than the Wellington or Wairarapa Fault earthquakes are likely to be and the second even smaller. Wellington can look forward to a quake which is likely to be at least an order of magnitude more devastating than the Canterbury quakes. 7.1 on the Richter Scale is at the low end of serious earthquakes.

Here’s why it’s a problem:

Historical data indicate that the Alpine Fault in general and its continuation in the Wellington area in particular are quite likely to be hit with an 8.0 or greater quake. The last Wellington one, 300-500 years ago, was 7.6 and the Wairarapa one in 1855 was 8.2. These weren’t quakes marginally larger than the Canterbury one. The Richter scale is not linear, it’s logarithmic. An increase of 1.0 means 10 times the ground movement and more than 30 times the energy released. Wellington is very likely to be hit by a quake 100 times more violent than Christchurch City suffered in February 2011. Or  greater. Quite possibly much greater.

We know the historical frequency of big earthquakes on those faults and we are now in the time zone for a repeat.

It gets worse

There’s been much made of the huge difference in the devastation between Haiti and that in Christchurch. Even if Wellington were struck by a quake of the same intensity as Port au Prince or Darfield the consequences would be much worse. Here’s why:

  1. The Haiti quake occurred smack-bang in the middle of a very large population centre. The first Canterbury earthquake was centred under tiny Darfield, over 40km from Christchurch. The city didn’t feel anything like the full effects of a 7.1 shake.
  2. Haiti is mostly hilly and unstable (remind you of anywhere?); Christchurch and the area of Canterbury most affected are as flat as a billiard table.
  3. Wellington is also very hilly and unstable, the Wellington fault line runs right through the centre of the city, and several other big faults run in parallel nearby.
  4. There’s a huge difference between being in a collapsing house on the flat and being in one perched on the side of a steep hill.
  5. Landslides are potentially more devastating and more lethal than the sand liquefaction that hit some Christchurch suburbs.
  6. The major fault line runs for miles along the only significant road and rail route in and out of Wellington city.
  7. My memory may need an update, but I’m reasonably certain that much of the emergency infrastructure is within a few hundred metres of the major fault line. The hospital, the Beehive, Civil Defence HQ, the Fire Station, et al
  8. Wellington has a much higher proportion of multi-story, high rise buildings and two story houses than Christchurch.
  9. A single slip blocking one side of the motorway brought Wellington to a halt for most of a day recently. Extrapolate that!
  10. Finally. Hope that when it comes, it doesn’t hit during working or commuting hours.

When it comes—presuming we don’t take drastic measures beforehand, like moving the Capital—it’s going to kill a lot of people. In monetary terms alone it’s going to cost at least 10 times more than Canterbury; quite possibly 30, 40 0r 50 times as much, or more. The human cost will be far greater.

It’s going to be bad.

Live in Wellington?

  • Don’t build anything in Wellington. Nothing. Not ever.
  • Buy your next house at least 40km east of the fault lines. And 20m above sea level.
  • Even better, get the house movers in. Tomorrow. Sections are cheap here in Whanganui.
  • On second thoughts, the Whanganui River is itself a fault line. Try Dunedin.
  • Oh dear, I think Dunedin’s in a caldera.  Oamaru?

It’s a worry.