7.0 earthquake hits New Zealand Sept 5, 2010 23:11:24 GMT -4
Post by gillianren on Sept 5, 2010 23:11:24 GMT -4
Hey, the ones here improve every time there's an earthquake now. It's just that retrofitting only solves so many ills, since old buildings are grandfathered in.
The radio was doing an interview with a structural engineer who has been working in the city inspecting buildings since the quake. He was saying that the majority of the severly damaged buildings were pre-1930s.
I'll bet. Hey, San Francisco buildings built after that point are safer, too; the state was handling earthquake codes by then.
Our engineers and law makers learned a lot that day and with knowledge that we are going to have 7-8's hitting most of our major cities (including the Capital, Wellington) given enough time, the decision was made to build to survive. The first building codes were introduced in 1932, and the first Building Act was in 1935.
Yeah, building codes are a Good Thing. It's what makes the casualty differences so major between an earthquake in the Greater Los Angeles Area and an earthquake in rural China.
Since then they have been revised several times based on what has been further learned from EQs in both NZ and overseas (including Kobe and Mexico City), with the latest update in 2004 when all non-residential buildings and multi-story residential buildings that were not up to the current regulations had to be strengthened to at least withstand a moderate Earthquake (one about a third of the size that a new building will withstand.) While this was to be a 10 year project with buildings to be compliant by 2014, many of the ones in Christchurch had been strengthened leading to their survival.
Do you know how that was going to be financed? I know one of the reasons a lot of things here in the US don't get retrofitted is that it can cost a lot of money to bring a building up to the new code. Also people wanting the state to keep its nose out of their property rights.
While the standards do mean that the exact type of quake varies depending on building type, ground type, and location in the country, I believe the current standard means that a building in NZ should survive a direct hit by an 8.0 earthquake long enough to evacuate it safetly, which is the goal, keep the building standing long enough for the people in it to get out alive.
Not all 8.0 earthquakes last long enough to evacuate a building. I mean, earthquakes really only shake for a minute or so tops most of the time. If it will stand that long after the shaking stops, so much the better. It is true, though, that stronger earthquakes tend to last longer, so I guess length would have to enter into it, too. Though I'll note that my mom's house has similar construction to a lot of the houses destroyed during the Loma Prieta quake in '89, and the most damage she's ever suffered was a chimney which had to be taken down after it got cracked in the Sierra Madre quake. ('91?) My mom's on bedrock, not on the fill of the Marina District of San Francisco, you see.