The New Zealand earthquake.

[Old Troop]

What is it that causes enormous casualties in some earthquakes and quakes of similar magnitude cause almost none in cities of the same size? Any ideas?

[Barack_America]

1. Construction standards. nt

[jpak]

3. Yup - Kiwis understand their island's geology and build to withstand quakes

n/t

[HiFructosePronSyrup]

2. Nature of the earthquake, and the nature of the buildings.

Poorly built buildings on sandy or marshy soil near the epicenter of shallow earthquakes are particularly bad combinations.

[hobbit709]

4. construction standards, geology of the ground at quake location.

[malaise]

5. Terrain, infrastructure, population size

and the enforcement of government regulations

[Hekate]

6. Strict building codes that get enforced by inspectors who can't be bribed.

Take it from a Californian. Photos of our damaged buildings show lots and lots of embedded steel rebar. You seldom see an actual collapsed building any more, and after the Northridge Earthquake took the facings off a bunch of buildings, I think that was added to the codes too. Huge numbers of existing public buildings have been retrofitted over the past 20 years.

Mud-brick villages simply collapse into rubble. Apartment houses in Peru completely pancaked one time -- it was impressive and actually almost terrifying to even look at: each floor simply landed on the one below it, boom-boom-boom, and there was almost no rebar to be seen.

A lot of places in the world have strong building codes, but lax enforcement and corrupt officials who look the other way when inferior concrete is used and other supplies are skimped on or eliminated.

Here in California building codes are so strict that if I even want to build a concrete block garden wall or retaining wall, if it goes over 3 feet high it has to have rebar.

Hekate

[malaise]

9. That's most important

http://www.abc.net.au/news/stories/2010/09/04/3002489.htm
That said, there is quite a lot of damage in Christchurch



A state of emergency has been declared in Christchurch, New Zealand, after a large 7.0 magnitude earthquake rocked the country's second largest city this morning.

The quake was felt throughout much of the South Island and southern parts of the North Island, and has caused widespread damage, including the collapse of some buildings.

It has also knocked out power and disrupted water and sewerage services.

Many people with injuries have sought treatment but hospitals say no-one has been killed.

Radio New Zealand reports Christchurch Hospital has treated two people seriously injured by falling masonry and glass, a number of people with broken bones, and others with minor injuries such as cuts and bruises.

[Hekate]

14. See the intact high-rise in the background? Yet the foregrounded 2-story has all of its outer walls

... gone. It could be construction -- it could be where the buildings sat vis-a-vis the tremor. I had friends in Northridge whose house was severely shaken (they lost all their glassware, everything was out of the cupboards) but not irreparably damaged. A street or so away in the same tract there were houses that were red-tagged as uninhabitable.

My heart goes out to the Kiwis.

Hekate

[malaise]

16. Good coverage here

http://www.radionz.co.nz/

[gateley]

7. I heard a geologist say "earthquakes don't kill people, buildings do". nt

[Warpy]

8. Depth has a lot to do with it

The quake in Haiti was a very shallow one. This one in NZ was something on the order of 20 miles down.

The buildings that sustained heavy damage so far all look like older construction, unreinforced brick and mortar walls, absolutely the worst thing in a quake. Unreinforced cement like they had in Haiti is second worst.

California quakes are usually very bad because most are quite shallow. The deeper the quake, the lighter the damage at the same magnitude.

[Old Troop]

10. Hmm. So it isn't handagod?

[Donnachaidh]

11. New Zealand has more sheep than people

Sparse population and good construction standards probably helps.

[Bobbieo]

12. I'm most concerned about my former neighbors who moved back to South Island,New Zealand

She sent photos of their new home perched on a cliff overlooking the sea. Hope I hear from her, soon.

[Ruby the Liberal]

13. Adding to the above about construction standards, it is depth

The closer to the surface, the more destructive.

[Brickbat]

15. Building codes and a lack of corruption.

It's that simple