The September 2010 and February 2011 earthquakes that shattered much of Christchurch, New Zealand, present cautionary lessons and examples for California and other earthquake prone regions, according to disaster expert and Professor of Architecture Mary Comerio.
She gave the annual Lawson Lecture at UC Berkeley to an attentive audience on the evening of Wednesday, May 4, 2011. The lecture is sponsored by the campus Seismological Laboratory.
In the aftermath of the February earthquake Comerio traveled to Christchurch—where she had previously spent a year as a visiting scholar—to help assess damage and document and study recovery efforts.
Major lessons from Christchurch, Comerio said, include: the importance of anticipating and planning for non-structural economic losses; taking a new look at earthquake hazards in areas outside known “high risk” zones; expecting a sequence of earthquakes rather than a single big event followed by recovery.
They also include coping with the long term effects when whole urban districts are shut down for months or years, large numbers of jobs—particularly in the service industry—are lost, and many residents are permanently displaced from their occupations and homes.
She also offered observations from Christchurch on the emerging role of social media in disaster response, and the importance of having sufficient trained personnel who can expertly assess damage and recommend response strategies after earthquakes.
Christchurch, a city of under 400,000 people on the east coast of the South Island of New Zealand is remarkably similar to some California settings, Comerio said. “It looks like Sacramento…it really looks like a US city, and parallels California in terms of growth.” As such, the earthquakes there are “an important lesson for us.”
Settlement in the region began around the 1860s, and Christchurch was, before the earthquake, a popular tourist destination and jumping off point for visitors to the more rugged western side of the South Island.
While the September earthquake—officially, the Darfield Earthquake—caused considerable damage in less settled areas outside the city, the February 6.3 magnitude event struck at the urbanized center of Christchurch.
The central business district was severely damaged and 114 blocks are now closed to public access. “Imagine an area that size closed”, she suggested, showing an overlay on much of downtown San Francisco. “And it will be closed for months, if not years.”
Within the damaged downtown there were thousands of companies doing business. Many of them have relocated and will recover, but “hotels, restaurants, retail—those jobs are gone”, said Comerio. It’s estimated that about 50% of the pre-earthquakes workforce in the downtown is now unemployed.
Much of the catastrophic damage was to mid-rise concrete buildings constructed in the 1980s, Comerio said. New Zealand has good earthquake engineering codes for buildings, but the codes for the Christchurch area anticipated earthquakes of less magnitude than those that actually occurred.
As a result, buildings believed to be structurally sound in design were damaged and will have to be demolished (“deconstructed” is the preferred term in New Zealand, Comerio said wryly). She showed photos of buildings, particularly hotels, up to 19 stories tall that were damaged and will have to come down.
In many cases they look intact the outside—perhaps with some broken windows and a few external cracks—but “on the inside have massive shear wall failure.” This was the result of only about eight seconds of severe ground shaking in February; in contrast, the recent Japanese earthquake shook for up to three minutes.
Ground liquefaction also played a major role in damage in downtown Christchurch. Soils shifted and sunk, and so did buildings. In one photograph Comerio showed a mid-rise condo building that was visibly tilting beside an office building inclining in the other direction. The multi-million dollar condos, “will have to come down”.
“Another really significant issue unique to this event was the collapse of the stairs” in many buildings, Comerio said. “We don’t understand yet what caused this mechanism.” Occupants of tall buildings are taught to head for the staircases in disasters, but in Christchurch some buildings stood while their staircases were reduced to rubble.
In addition to the more modern mid-rise buildings that were damaged, hundreds of older unreinforced masonry (URM) buildings were damaged or collapsed, causing more than 40 deaths. Comerio postulated that the death toll was lower because many buildings partially damaged in September had not been re-occupied by the February earthquake. Having gone through the September quake people also knew how to quickly take cover or get out of the way of hazards when a quake occurred.
Christchurch did have an ordinance addressing reinforcement of URM buildings, she said, but it was voluntary, and only about 7-12% of older buildings had been retrofitted. Some unreinforced older structures did survive with little damage, but many collapsed, creating some of the more dramatic post-earthquake images showing stone or brick walls crumbled into streets.
The Downtown area is now cordoned off and not accessible to the public, Comerio said. There are “350 buildings that the City will demolish”. The city has taken over responsibility for managing the demolitions in part because “it’s much faster to demolish while the cordon is in place” around the area.
One challenge has been stabilizing buildings near collapse while they await controlled demolition. There are buildings 10 or more stories high that had to be “propped up until they can be taken down”, Comerio said.
Outside the downtown, damage was widespread in residential suburbs. There was “enormously bad liquefaction in the suburbs.”
Liquefaction—when what seems to be solid soil essentially turns to watery jelly during an earthquake—occurred because “Christchurch is essentially a swamp”, Comerio said. “All the primary documents (from when the area was settled) describe slogging through the muck.”
As a result, buildings shook severely and the ground sank as much as a meter in some areas. Buried layers of sand erupted to the surface in many residential neighborhoods.
While some severely damaged neighborhoods were old, others were built in the recent past. “Some of them were new developments that should never have been allowed to be built”, she noted. “There were some subdivisions that were political embarrassments. No one can explain what was happening when they approved those subdivisions.”
“There will probably be at least 10,000 homes that will not be rebuilt”, she said, and the city is considering not allowing rebuilding in some areas.
In residential districts building codes were good and buildings did not come apart because of the shaking. “Generally the wood frame houses are very well built. It wasn’t structure that was the issue, it was liquefaction.”
This also applied to non-residential facilities. One hospital, Comerio noted, has a main building that is a state of the art base-isolated structure. It survived without structural damage, but much of the functioning of the hospital complex was paralyzed by other damage.
Some emergency generators couldn’t start because they were contaminated with sand. Fire sprinker systems broke, flooding some wards. Health care records were scattered. The hospital laundry lost water and power. Many patients had to be moved and surgical procedures postponed.
“It has a ripple effect through the whole health care system”, Comerio said, even when the hospital building itself is standing and appears to be intact.
There was “lots and lots of non-structural damage” in Christchurch, Comerio emphasized.
Streets and infrastructure were damaged. Pavements and pathways buckled or shifted horizontally. In shops, factories, offices, and homes, goods, equipment, and belongings were broken and scattered or made inaccessible. She showed pictures of a warehouse where enormous qualities of stacked items had collapsed in a jumble.
In business offices, records and equipment were scattered. Equipment in research laboratories was damaged. Mechanical equipment broke loose from footings or attachments. Library collections were thrown into chaos.
Even when the buildings are reusable or repairable, the contents have to be sorted out again and broken items replaced before the facilities are fully functional.
In many places the primary damage was to ceilings, partitions, interior finishes and fixtures. It may not seem like much, Comerio said, “but it was messy stuff, and it had to be redone.” The most severe window damage was often to large, ground level, windows such as storefronts. However, “there wasn’t a rain of glass down from the tall buildings,” Comerio said.
“Even with modest ground shaking buildings built to code sustain a lot of economic loss”, Comerio concluded, a factor not necessarily taken into account in conventional post-disaster planning.
She also emphasized the importance of preparing for a sequence of disaster events in the same place, rather than simply assuming there will be one disaster, followed by a period of recovery. Since September, there have been 18 aftershocks measuring 5.0 or larger in the Christchurch region, including the February quake.
In the case of urban Christchurch, the February earthquake did considerably more damage than the September event. Buildings that had been fine after September were wrecked four months later, and the areas of concentrated damage shifted.
“This is a serious issue” says Comerio. “We tend to think about the singular events”, but the Christchurch earthquakes show that the disasters can keep on coming in a concentrated area, compounding damage and disrupting both recovery efforts. She described going into buildings to inspect damage while someone waited outside with a bullhorn, ready to shout an evacuation warning if an aftershock started.
Rock slides and falling boulders were a problem in hilly areas near Christchurch, and continue months after the major quakes. Rocks are still coming down, some cliffs below or behind homes are unstable, and crews are busy trying to stabilize the most hazardous areas.
The restoration of public infrastructure is underway, but some of it has proceeded slowly. Comerio said that not only did breaks in sewer and water lines have to be repaired, but the pipes had to be cleared of sand and silt which had clogged them during the earthquake.
“There was actually no water for about two to three weeks” in many areas, and residents had to rely entirely on bottled water. Water service is now restored in most cases, but it’s not necessarily potable water.
Many sanitary sewers were severely damaged. In response, “the city just plunked a bunch of portapotties along the street and that’s what people use” said Comerio, showing a photograph of a street lined with the distinctive plastic kiosks. “People are still operating in a very makeshift way. There are no tent cities, but you have to go outside at night to the portapotties.”
In contrast to the sewer and water systems damage, “power did pretty well” said Comerio. “It went out but was back on within a day or so.” Telecommunications services were also less disrupted than other utilities, she said, but also noted an unexpected temporary consequence.
Because mobile telecommunications became essential and heavily used after the earthquake, the government “cut the bandwidth for e-mail to increase the band width for cell phones”, something she and her colleagues discovered as they tried to check and send electronic messages.
Comerio added that social media had played an unexpected and robust role in disaster response. In conventional disaster scenarios, people are expected to wait for top-down information from knowledgeable officials. In Christchurch, people often organized themselves and then the official institutions later disseminated information about what was being done.
Comerio said young people used social media to organize impromptu but effective responses. For example, in many areas where large amounts of sand had come to the surface, university students coordinated teams of volunteers who cleared streets by shoveling the sand into manageable piles. The city later came with heavy equipment and hauled the collected sand off to dump sites.
The earthquakes have had an effect on the population of Christchurch, Comerio said. Unlike the Japanese earthquake and tsunami the death toll wasn’t high, but as many as 50,000 people are now “gone” from the Christchurch area, she said. The loss of jobs has probably caused many of the relocations, even when homes were still usable.
Many homes, both damaged and habitable, in the Christchurch area now sit vacant. It’s “a New Orleans issue”, she said.
Over 200 primary and secondary schools and more than 400 child care facilities were initially affected and closed by the earthquakes. Most of them have now come back into use, but some remain damaged and closed, with students doubling up in operable schools.
Right after the February earthquake, Comerio said, some 8,000 students were taken out of the closed schools and re-enrolled by their parents in school districts outside the Christchurch area. “Very few” of those have returned to their now reopened schools.
In terms of higher education facilities—a subject of considerable interest to a Berkeley audience—Comerio outlined damage and recovery efforts at the University of Canterbury, which had about 20,000 students.
September earthquake damage there was primarily non-structural, and the campus was able to re-open after about two weeks. After the more severe February earthquake it was closed for 3-4 weeks, and finally reopened “with all the teaching in tents and temporary buildings,” Comerio said, showing a photograph of tents in parking lots.
According to a campus map Comerio showed, perhaps half of the buildings are still closed as the institution meticulously tries to identify and correct hazards.
They said “we’re losing confidence in what a ‘green tag’ means”, she said, referring to the standard indication that a building has been structurally evaluated and is safe to enter. The University is now pursing a policy that “we’re going to guarantee the safety of the campus” before business as usual resumes.
Many faculty and staff have only had 20 minutes at a time to go into offices and laboratories to recover some essential materials. There was considerable non-structural damage to building contents and finishes. Some students have been relocated to Australia.
In her wrap up of lessons from the Christchurch quakes, Comerio focused on some of the long term planning issues in other regions where earthquakes might occur.
New Zealand is very familiar with earthquakes reaching magnitudes over 7.0, she noted, but the previously unidentified fault that broke under Christchurch had not experienced a major earthquake in some 16,000 years. On the South Island, much of the earthquake scenarios had focused on the Alpine Fault zone in the mountainous western part of the island.
There was “no obvious precursor activity” to the Christchurch quakes, she said. “Christchurch is in one of the lower hazard seismic zones.” But the Darfield earthquake broke the ground for 30 kilometers and causing surface movement up to four meters along the fault trace, and the February earthquake did catastrophic damage to the city.
This has implications all over the world, Comerio said, including North America. She displayed a large map of fault hazard zones in the United States, noting that a lot of regions around the perimeter of high hazard areas may be at greater risk for damage than previously assumed.
Those areas are “much less prepared”, she noted. “They’re going to see damage that will look a lot like Christchurch.”
“What really worries me is we’re investing an enormous amount of money in preparing for earthquakes in the high risk zones and not much in the moderate risk zones”, she said. “Are we putting our energies in all the right places?”
“Moderate earthquakes can cause an awful lot of damage”, she emphasized. “We have to have enough mitigation in moderate zones” and we need to “really improve our educational capacity about the power of earthquakes.”
Other lessons from Christchurch were the importance of taking into account non-structural economic losses such as business interruptions. How do you effectively manage both risk and recovery, she asked.
Are building owners willing to pay up front for improved performance? Only about 11% of California homeowners have earthquake insurance, she noted, and there in California alone there are about 20,000 older concrete buildings, “just like the buildings in New Zealand” that were often damaged beyond repair.
In our Bay Area, she said, the anticipated earthquakes will likely cause “an enormous amount of low income housing damage.” We’re going to have a huge impact.” As many as 100,000 apartment units may be damaged or destroyed in the East Bay.
In Christchurch, she said, over the next three to five year period “construction industries will do well”, but other economic engines, such as tourism and the hospitality industry, may be “out for years.”
People have insurance, but once the claims are paid, “will the capital come back” to the city? Insurance doesn’t guarantee anyone will rebuild, or that financial institutions will be willing to invest in new building or development in the damaged areas.
And if someone is paid for the damage to their building but the site can’t be built on again, they’ve suffered an uncompensated economic loss beyond the structural damage.
There are also policy implications for urban planning. In Christchurch, Comerio noted, the Mayor is saying “I’ll never let another high rise building be built here again.” Tall buildings may yet be built, she said, but the city will probably will probably have more stringent limits on height.
Some of the areas downtown most damaged by liquefaction are along a river, and its possible a greenbelt there will be widened. The city is intent on doing a plan for the Central Business District, she said, but they are “trying to get a practical plan in place, not fanciful urban redevelopment schemes.”
A group of Christchurch government leaders would soon be making a visit to the Bay Area to talk with local governments here about lessons for disaster planning, Comerio said.
And we would all, individually and in our communities, organizations, and institutions, benefit from paying more attention to the inevitable approaching natural disasters and how to cope with and recover from them.
The Christchurch Earthquake occurred on February 22, 2011 with a magnitude of 6.3. About 180 people died. It was preceded by the September 4, 2011, magnitude 7.1 Darfield Earthquake on the Canterbury Plains west of Christchurch.
The Lawson Lecture at UC Berkeley has been given annually since 2003 by a noted seismologist or earthquake expert in a related field. It focuses on a topic of recent research (often a recent major earthquake) and honors Professor of Geology, Andrew Lawson. Lawson led scientific investigative efforts and studies following the 1906 San Francisco Earthquake and is regarded as the father of modern seismology. The lectures “address a wide variety of earthquake issues of interest to the Berkeley community.”
See the Lawson lecture website for announcements and video of past lectures.