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New Zealand shows even strong building codes are no match for monster earthquake, experts say [Update]

New Zealand earthquake: Christchurch airport plans to reopen Wednesday; extra flights added

The devastation and loss of life in the Christchurch, New Zealand, quakes offer some sober lessons for California, earthquake experts said.

Click here to view an interactive on the New Zealand quake The damage shows that a sharp earthquake in a highly vulnerable area can get the better of strong seismic safety codes.

“If the dart lands right on you, it generates intense shaking and a lot of buildings that we think are safe turn out to not be safe,” said Susan Hough, seismologist with the U.S. Geological Survey.

The quake’s epicenter occurred less than six miles from the center of Christchurch, New Zealand’s second-largest city, far closer than a 7.0 quake in September, which had an epicenter about 30 miles away and resulted in no deaths.

 Also, the highest ground acceleration recorded was greater than 2G, or twice the acceleration of gravity –- which would make Tuesday’s quake among the most powerful in terms of ground-shaking acceleration on record, said Hough. It was strong enough to throw objects in the air.

“There’s only a handful of records of shaking” as strong as 2G, Hough said. “That’s quite extreme shaking.… Some earthquakes just have stronger shaking that affects buildings.”
By contrast, the ground shaking in the 6.7 Northridge quake in 1994 was less, recorded at 1.7G, Hough said. Hough has estimated that the strongest ground shaking in Port-au-Prince in the Haiti earthquake in 2010 was only about 0.5G.
Among the buildings destroyed in the quake were the Pyne Gould Guinness Building, which is described by local media as one of Christchurch’s best-known office towers, the Canterbury Television building, and the spire of the century-old Christ Church Cathedral. Staffers at The Press newspaper in Christchurch were trapped as part of the 102-year-old building collapsed, the newspaper reported.
Hough said it appears that some of the buildings that collapsed are fairly modern, which, “to me, says that we still have some things to learn.” She noted that during the 1971 earthquake in Sylmar, Olive View Hospital collapsed, even though it had just been built; earthquake scientists also discovered after the 1994 earthquake in Northridge that some of the welds in steel frame buildings weren’t as strong as previously thought.
“In this case, I strongly suspect the accelerations just exceeded the design values,” Hough said. As recently as the 1980s, seismologists had believed that earthquakes couldn’t generally produce ground accelerations greater than about 0.5G. But scientists began understanding that ground accelerations could be much stronger after reviewing new data from newly constructed earthquake monitoring stations.

Hough said Tuesday’s quake offers a lesson in humility to California, showing what can happen when a quake is centered so close to the city center and populated by dense structures, some relatively new, and some historic.
Thomas Jordan, director of the Southern California Earthquake Center at USC, said Christchurch was devastated in large part because of the shallowness of the quake, and the fact that the strongest shaking occurred precisely in the location of the city’s downtown area.

“It’s really the fact that you had a lot of buildings very close to the very strongest hypocenter, which means the strongest shaking was right there in town,” Jordan said.
Another question is how very tall buildings in California would fare in a big earthquake, particularly the long period of booming and shaking, roughly similar to the low tones in music. “We don’t have a lot of observations of how modern tall buildings will perform in really big earthquakes,” Hough said.
There are other buildings in California whose vulnerabilities in quakes are well-known, such as multi-unit condos and apartment buildings with tuck-under parking. They are vulnerable because their first floor lacks a wall that would help keep the building from toppling in a quake, Hough said.
Los Angeles has enacted an ordinance that has required bracing of unreinforced masonry buildings, Hough said. But other municipalities haven’t enacted such requirements, although state law does require unreinforced masonry buildings in California to have signs posted warning about their condition.
In 2003, a quake that rocked California’s Central Coast killed two men in Paso Robles, when the roof of a 19th-century building collapsed on them. Farther north, parts of the 19th-century Mission San Miguel collapsed.

[Updated at 8:55 a.m.: In Christchurch, Jason Ingham was preparing for a seminar on earthquake building standards Tuesday afternoon New Zealand time when the hotel where he was staying began to shake. He and his colleagues from the University of Auckland had studied damaged structures after the last Christchurch quake, which struck in September of last year. But he said they could feel immediately that Tuesday’s quake was more intense.

And while most of the damage last time occurred to unreinforced masonry buildings, many modern buildings were damaged Tuesday, said Ingham, who is an associate professor of civil engineering.

“Our instinct is that this exceeded the loads that even the modern buildings were designed for. We are almost certain,” said Ingham. “The assumption is that an earthquake of this size would have caused damage in any modern city anywhere.” ]

[Updated, 9:08 p.m.: New Zealand quake raises questions about L.A. ]


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New Zealand earthquake surprises experts with its level of destruction; California parallels seen

-- Rong-Gong Lin II and Sam Allen

Photo: A hostel for backpackers in Christchurch was damaged by the quake Tuesday. Credit: Simon Baker / Reuters

Comments () | Archives (32)

Stop with the "it's coming" comments. I've heard those for the last 40 years. When it happens it will happen. You not adding anything new or relevant!!

What about liquefaction as contributing cause of Christchurch devastation?

I'm about 15 miles from the 1994 Northridge earthquake & there was stark difference between homes build on bedrock (like where I am) and those built in natural riverbeds (such as Simi Valley).

See 2nd comment from John Gurr in this BBC Christchurch earthquake article:


For future reference, the Northridge quake was actually centered in *Reseda* and it was named the Northridge quake due to the massive damage that was sustained there.

And to 20-20 LBH3, do you have a citation for your story about the 1992 Cape Mendocino quake or is this the stuff of "happened to a friend of a friend of a friend?"

What has happened in Christchurch is so sad and tragic. Our hearts and prayers go out to the Kiwis.

When the "Big One" hits Los Angeles and Southern California, however, it will make this quake and 9/11 seem like "child's play" in terms of fatalities and physical damage. For example, the steel joints in many high-rise office buildings were apparently weakened by the 1994 Northridge earthquake, and nothing has been done to repair them. To remove tenants from the buildings, while the potentially-critical work is underway, was deemed to be politically and economically unpalatable. Thus, the problems were swept under the rug and never addressed by building owners and the city’s politicians. Los Angeles may rue the day that this happened.

See http://naegeleblog.wordpress.com/2010/09/08/earthquakes-the-big-one-is-coming-to-at-least-los-angeles/

I had to drive through the center of Christchurch yesterday,and can say that the damage was not only caused by the actual quake,but the way the ground turned to jello at the moment it happened.Some even new buildings are damaged and no building code can stop that....if the ground underneath goes liquid.One of the weirdest things I saw driving home an hour after it happened,was a Toyota 4x4 that someone had driven over a wide grass median strip between the lanes...its late summer here and what had been hard,dry ground had literally turned instantly to quicksand...the vehicle was buried up to its belly in the stuff.

Another major difference between the September 4 Christchurch quake and this one is that the earlier one happened on a Saturday morning before dawn, when the CBD was virtually deserted. Tuesday's, by contrast, hit at lunchtime on a business day.

Traumatic as the September temblor was, most people still did not stock up on emergency supplies afterward. Water, flashlights, candles, tinned food, something to cook with, battery-powered radio, a shovel to dig a latrine with when you can't use your toilets, medicines, blah blah blah.

This article strikes me somewhat alarmist, though there are some valid points. Still, after looking at picture after picture of the earthquake in Christchurch it is very obvious that many of those buildings were not designed to a rigorous earthquake code--many I saw were unreinforced brick buildings, that crumble quite easily as they did in San Francisco in 1906. Ignoring the 0.5G theories being espoused by Ms. Hough, the explanation is fairly straightforward--many buildings were old and built before any type of earthquake codes were in place. This happened recently here with the Chino Hills earthquake when cities near the epicenter (such as Chino Hills, a newer city built to code) escaped unscathed while older buildings farther away (such as Pomona) and even newer but poorly designed buildings as far away as the San Fernando Valley/Ventura Coutny and Orange County suffered extensive damage. In New Zealand it appears the latter is the same--new buildings built or designed shoddily, along with older unreinforced brick buildings.

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