Life at the epicentre

  • Illustration by Randy Ortiz
  • Tom Heaton, Caltech Seismologist. Image credit: Kyle Christy
  • Illustration by Randy Ortiz
  • Illustration by Randy Ortiz
  • Seismologist Elizabeth Cochran specialises in earthquake physics. Her Quake-Catcher motion sensors attach to home computers, turning them into a network of seismic stations.
  • The Ceres-Tulbagh earthquake. The most destructive earthquake in South African history struck the Ceres area in the Witzenberg Mountain range on 29 September 1969. Its magnitude was 6,3 on the Richter scale. Shock waves were felt as far as Durban (1 175 km). The earthquake was followed by a number of aftershocks, the most severe of which was on 14 of April 1970 (5,7). Here the devastation is clearly visible on these buildings. Image credit: Die Burger/Gallo Images
Date:27 September 2012 Tags:, , , ,

Earthquakes are inevitable, but very few people living near a major fault take steps to protect their families and homes. Preparing for the big one can mean the difference between safely riding it out – or losing everything. – By Kalee Thompson

The peeps were moving. It was Easter Day, 2010, and I was at a potluck brunch not far from downtown Los Angeles. It was characteristically sunny and warm, and many of the guests had settled into the host’s backyard garden. I was one of a half-dozen people sitting at a wooden picnic table when the shaking began. At first I thought it might be nausea. I was four months pregnant and had already eaten one too many of the sugary marshmallow chicks. Then I saw that everything on the table was vibrating. Earthquake.

Little about it was scary. In fact, the sensation was mildly pleasant, just a mellow undulation, like standing on a floating dock as a spent motorboat wake rolls through. In seconds, it was over.

Soon other guests filed out of the house. “Did you feel that?” people asked one another. A lot of them hadn’t noticed a thing, but I was thrilled. After three years in LA, it was my first true earthquake. Phones were fished from pockets and purses and Twitter feeds consulted. This was the real thing, a 7,2-magnitude tremor that originated in Mexico, 10 kilometres beneath the Baja Peninsula. There was some damage near the border, but Los Angeles had been spared.

A few days later, my husband, Dan, and I were sitting in our living room when an aftershock hit. We briefly locked eyes, then turned our gaze to the darkened TV. We had recently bought our first flat-screen, and dutifully used cheap earthquake straps to secure it to the mantel above our defunct fireplace. They worked. The shaking stopped. Everything was fine.

The past 20 years have been turbulent ones for the planet. Earthquakes have caused massive devastation, killing 86 000 people in Pakistan in 2005; 87 000 in China in 2008; and close to 100 000 in Haiti in 2010. In the two highest-profile earthquakes of the past decade – the 2004 Sumatra quake and the 2011 Tohoku event in Japan – most of the death and destruction were caused by a subsequent tsunami. Four of the 13 most deadly earthquakes in history have occurred since 2004 – a statistic that says less about Earth than about how humans live on it. Growing populations and dense urban centres create greater hazards from natural disasters. (Even the strongest earthquake poses little danger to a person alone in a field.) When major quakes strike, as they inevitably will, people-packed cities like LA are most vulnerable.

Long before I moved to California I knew that earthquake-probability maps show the Pacific Coast traced in red, reflecting the major fault lines that form where tectonic plates abut. But until recently, I hadn’t looked into the specifics: aseismologists estimate there’s an 82 per cent chance that a magnitude-7 or greater quake will hit directly beneath Southern California in the next 30 years. Three-quarters of all US earthquake losses are expected to occur in the state, and experts’ best-guess estimate is that damages will exceed R250 billion per decade on average.

Meanwhile, Americans have been reminded that earthquakes aren’t purely a California hazard. In August 2011, a 5,8-magnitude tremor struck near Richmond, Virginia. That quake, felt from Georgia to Quebec, was the largest to hit the Southeast in more than a century.

Using new paleoseismic data and more complex computer- forecasting techniques, the US Geological Survey is refining risk estimates for places such as the Cascadia subduction zone off the Pacific Northwest coast, the Wasatch fault near Salt Lake City, and the New Madrid seismic zone, extending from southern Illinois into Arkansas, which experienced four magnitude-7 quakes back in 1811 and 1812. Of course, probabilities tend to have less impact than personal memory of actual events, and throughout the US, it’s been a time of relative quiet. The last earthquake to cause significant havoc was the 6,7-magnitude Northridge quake, which killed 57 people and delivered more than R160 billion in damage to the Los Angeles area in 1994. That mild Easter Sunday tremor in 2010 turns out to have been the most powerful earthquake to touch Southern California in nearly 20 years.

The same month, Dan and I were in the the property was charming: a peak-roofed, light-filled house perched atop an ivy-smothered slope. We didn’t mind the steep, uneven stairs that led to the front door, or the cracks in the flaking plaster and the concrete patio. For a house built in 1927, such scars seemed minor.

We were pleased to learn that the building had been bolted, the foundation attached to the wooden frame with a series of struts and bolts. The job wasn’t to current building regulations, but overall it looked pretty good, our home inspector told us.

We reviewed insurance options. Earthquake insurance would more than double the cost of basic insurance. We had a decent idea of worst-case scenarios: friends had been “redtagged” after Northridge, when authorities marked 1 600 homes as uninhabitable and forbade residents to return.

Still, what were the chances of that happening again? Of it happening to us? Looking more closely at the quote, I saw that the excess for our home would be more than R400 000. Justifying the decision to forgo earthquake insurance wasn’t difficult. The house has held up for this long, we rationalised. Something truly catastrophic would have to happen to make that expense worthwhile.

Still, earthly hazards had seized my attention. In the past, I’d been exasperated by my East Coast family’s concerned phone calls following news coverage of Southern California’s forest fires. “That’s nowhere near us! We’re completely safe,” I’d reassure them (though once we could see distant flames from our apartment’s front porch).

Now, though, I was the one worrying. The financial gamble of homeownership was part of it. The other was my son, Otto, who was born a few months after we moved into our new home. For the first time, I compiled a household earthquake kit, adding a week’s worth of extra diapers, wipes and baby food to the stockpile of water, torches and first-aid supplies. I made room in the boot of our hatchback for a basic survival kit including energy bars, a fire extinguisher, sneakers, more diapers and a couple of 10-litre water containers, and studied the emergency-shut-off directions for our gas line and water heater.

When the 9,0-magnitude earthquake, tsunami and nuclear disaster struck Japan in March 2011, Dan and I half-jokingly debated the pros and cons of stocking up on plastic sheeting and duct tape. Nuclear disaster planners recommend a shelter-in-place approach to radiation plumes. But our house has neither a real basement nor any windowless rooms. Maybe sealing off our draughty, old- fashioned swing-open windows would help?

Did we think dangerous fallout from the Fukushima Daiichi power plant might actually stretch across the Pacific? (Some members of an online moms’ group I lurked in were convinced it was already happening.) Or were we more concerned about a similar “unforeseen” disaster at the San Onofre nuclear power plant 100 kilometres to the south? (News that it had been built to withstand a magnitude-7 earthquake suddenly didn’t sound so impressive.) I’m not really sure. Both of those possibilities seemed outrageously unlikely, yet it was foolish to completely dismiss them. What I knew to be true was that radiation exposure poses especially high risks for small children. Otto was six months old.

When I saw a flier advertising a free emergency- preparedness class at the local library, I signed up. Over seven evenings, I sat between an elderly Japanese couple and a row of ageing hippie types as a firefighter schooled us on various disaster scenarios. We practised triage and first aid with what struck me as a somewhat lofty idea that when the big one hit, all of us – informed, diligent citizens that we were – would be providing crucial backup to first responders. Gory videos of car crashes and building collapses were the backdrop to discussions on how to treat head trauma (the No. 1 earthquake injury, our instructor said); how to make or find potable water when utilities are cut off (mine your water heater); and the California laws governing defecating in your own yard (illegal! my live-free-or-die New Hampshire relatives would be outraged). But I also had a more fundamental question about earthquakes: what were the odds I’d ever have to use these skills?

In more than 30 years at the California Institute of Technology, seismologist Tom Heaton has developed a reputation as something of an earthquake maverick, with expertise in both geophysics and engineering. He’s a large man, with suspenders that stretch over his neatly pressed dress shirt and a soft, jowly face framed by a cloud-like crown of white hair. I’m hoping Heaton will provide some straightforward facts to help me frame our mutual earthquake risk. Instead, he leans back, obviously bemused by a question he’s heard too many times before. “It’s almost like asking how big is the risk from wars, how big is the risk from epidemics,” Heaton says. “When we look at the statistics of earthquake problems, they’re the kind where things that don’t happen very often end up being incredibly important.”

Recent US seismic history doesn’t give us any real clues as to what lies ahead, Heaton says. “In the last century, we’ve only had deaths in the hundreds. But if you look at 1906, the largest city in the western US was basically wiped out by an earthquake. Losing a major city would be hard for somebody to even imagine today. Maybe some people would say that it’s impossible. But I don’t think anybody actually knows that.”

I ask Heaton what he thinks about my earthquake-insurance rationalisation – that my house has endured 80 years of shaking, and so can probably hold up for the four or five more decades that Dan and I will be around. He smiles. “Oh no, that doesn’t really tell you anything,” he says. It’s no accident that earthquake-probability forecasts use a 30-year time frame, the same as the typical home mortgage. Heaton has been intimately involved with the complex number-crunching responsible for those statistics, and although the figures undoubtedly help citizens evaluate risk – and engineers set building standards – he is the first to admit that the forecasts are perplexingly vague.

“I’ve fallen asleep a hundred times with those numbers,” he says. “We argue and arm- wrestle. There’s a million compromises.” A magnitude-7 quake, after all, may be a neighbourhood-flattening jolt or just another fun party story, depending on where and when it comes.

Heaton has raised three children in a home built in 1910. He doesn’t have earthquake insurance either. He used to, up until 1991, the year the 5,6-magnitude Sierra Madre earthquake damaged his home. “It broke some foundation; it destroyed the chimney,” he says. “By the time it was done, it caused several tens of thousands of dollars in damage, and earthquake insurance paid for that. It was a good deal.” Since then, the price of earthquake insurance has gone up, along with excess payments. Heaton and plenty of other Californians calculated that it made more sense to invest in upgrades that would protect against future quakes than to pay a skyrocketing monthly premium.

Though it’s our homes we fret about most, they’re usually the least vulnerable – at least single-family, wood-frame houses like the ones Heaton and I own. “Wooden houses are extremely resilient to earthquake shaking. It’s almost unheard of that they actually collapse,” he says. Far more dangerous are unreinforced brick structures and what engineers refer to as nonductile concrete buildings. Had the Northridge earthquake occurred during the workday rather than at 4:30 am, studies concluded, there would have been 20 to 30 times the fatalities.

The same principle will likely apply when the inevitable big one strikes. A study that simulated a 7,9-magnitude rupture on the San Andreas fault (a repeat of the 1906 San Francisco quake) calculated that 8 000 people would be seriously injured and 1 800 killed if it occurred at night. If it struck during the day? Expect 12 500 injured and 3 400 dead.

Not long after the Japan disaster, I fell into conversation with the wife of a University of California, Los Angeles, seismologist at a friend’s housewarming. Her husband, the woman told me, had been part of a study that identified the most collapse-prone buildings in LA. Maps existed, but city officials didn’t want the public to know about them. In the weeks that followed, I often found myself examining buildings as I drove LA’s surface streets, looking for signs of seismic reinforcement. In restaurants and shops, I’d try to guess the age of brick and concrete, wondering if I might be lingering over a sandwich inside a structure on the secret danger list.

Eventually I tracked down the study in question, as well as one of its lead authors, Mary Comerio, a professor of architecture at the University of California, Berkeley. In her view, the building list wasn’t quite the scandal I’d imagined over my second glass of wine. It’s a research database that was never meant to be public, she tells me. The effort is part of a much larger project tasked with figuring out how to classify concrete buildings by their risk level.

The number of potentially hazardous buildings in Los Angeles is small compared with that of many other cities, Comerio says. “Los Angeles has had a very aggressive public retrofit programme. Every public building in the city has either been retrofitted or replaced.” Because of what she calls LA’s big adaptive re-use programme (also known as the downtown hipster invasion), lots of warehouses have been converted to residential lofts; planning regulations requires that such change-of-use conversions be seismically retrofitted. It turns out that Los Angeles’ future-oriented, growth-focused character makes it a safer place to live. “Los Angeles, frankly, tears down more buildings than a city like San Francisco,” Comerio says. The latter has about 3 000 nonductile concrete buildings, twice the number in LA.

I still wondered why the inventory couldn’t be made public. When the research is complete, it will go into an open database. The building addresses, though, will be stripped out. “There are privacy issues,” Comerio says. “The minute it gets in the public realm, somebody is going to say, this is a list of dangerous buildings. That’s not what we’re saying; we’re saying this is a list of buildings we’re studying.”

Heaton had been less politic when I posed a similar question to him at Caltech: say you wanted to rent an office space in downtown Los Angeles. Is there a database that could help you identify which buildings are more or less safe? “No, you’re toast. You’re hosed,” he said. “There should be, but the politics of it are such that nobody has been able to push that through.”

Determined to improve my own assessment skills, I meet seismic engineer Aaron Reynolds in the lobby of the Walt Disney Concert Hall. Reynolds’s firm designs hospitals and schools and retrofits older buildings for seismic safety. As the result of improved building regulations, it’s typically not the primary structures that are the problem these days, he tells me. In recent decades, nonstructural damage, such as broken ducts and water pipes, has been more costly.

“I think there’s a lot of confidence that (newer) buildings are going to perform fairly well,” Reynolds says as we stand on the sidewalk beneath Frank Gehry’s glimmering suspended-metal sails, gazing towards the compact cluster of downtown skyscrapers. “Collapse is just unacceptable.”

We walk a few blocks to Temple Street and the city’s fortress-like Roman Catholic cathedral. Reynolds stops a short distance from the exterior wall and points out a small gap in the pavement; it marks the edge of the narrow concrete moat surrounding the building’s base. He makes acrude sketch on his iPad. The monolith rests on rubber cylinders known as base isolators, which act as a suspension system for the entire structure. During an earthquake, the isolators will absorb most of the energy.

The moat of concrete is designed to shift as needed – a metre or more – to give the building room to move. “Everybody jokes about the drunk person in an accident; he’s the one who doesn’t get hurt,” Reynolds says as the cathedral’s bells begin to chime. “It’s the person who’s not drunk who ends up being injured because he stiffens up.” A building is similar. “Stiff buildings absorb a lot of earthquake energy. With the isolation system we make it soft.”

In the aftermath of the Tõhoku disaster, I kept hearing how Japan had the most advanced earthquake-early-warning system in the world. Information from a vast network of sensors automatically stops trains, shuts down utilities, and sends text and e-mail alerts to citizens soon after a significant quake begins. The lead time is typically just tens of seconds, the time between a fault slipping and the ground waves hitting population centres. But that’s enough to save lives.

Scientists have talked about installing an early-warning system in California for decades, but the political will is lacking. It may be that society still holds out hope for true prediction, a word I find causes most seismologists to take a deep, nerve-calming breath.

Despite reports of prescient runaway pets, we remain unable to predict specific seismic events. Early warning is our best hope, but experts are pessimistic that the funding (more than R600 million) will materialise before another big quake hits. “If you look at the systems in other countries, they’re generally a result of a killer earthquake,” USGS seismologist Doug Given says. “The Mexican system resulted from the ’85 earthquake that killed about 9 500 people. The Japanese system was the result of Kobe, which killed 6 400 in 1995. It’s our hope that a bunch of Americans don’t have to be killed before we build one.”

Elizabeth Cochran’s office is a 5-minute walk from Heaton’s on the Caltech campus. Cochran invented the Quake-Catcher Network, a citizen science project in which thousands of people attach matchbook-sized sensors to their desktop computers. When many sensors in close proximity detect similar shaking at the same time, it’s likely a real quake rather than random jostling. The day before my visit, there had been a 4,0-magnitude earthquake north of San Francisco; within 8 seconds, Quake-Catcher data pegged it at a fairly accurate 3,7. “The idea is that once, or if, it’s found to be reliable, this could feed into an early- warning system,” Cochran says.

After an earthquake, seismologists create shake maps that show the strength of the ground motion in different areas. “Right now those are highly interpolated,” she says. “There are stations 50 kilometres apart and you’re essentially guessing the ground motions in between.” A vast network of Quake-Catcher sensors could add valuable resolution to those maps, identifying where to send firefighters, EMTs and transportation inspectors first.

I leave Cochran’s office with a sensor of my own. Over the next few weeks, I work on my family’s earthquake kit, stashing several extra 25-litre water containers in the backyard. I rearrange the furniture in Otto’s bedroom so that his crib is no longer next to the pane-glass windows.

I also call two different retrofitting specialists to take a closer look at that ad hoc bolting job beneath our house. Contractor One seems genuinely impressed by the work and tells me that if it were his house, he wouldn’t do anything more. Contractor Two, a well-respected local named Greg Sylvis, has specialised in retrofitting for three decades. He is more critical.

“A lot of times they’ll just do the part you can see from the door,” Sylvis says as he pulls on kneepads, a headlamp, and a face mask, then shimmies into the 30-cm high crawlspace at the rear of the house, over soil littered with ancient bottles and rodent droppings. He finds no shortage of hardware, but much of it is extraneous, installed on interior posts, which won’t help in an earthquake. The bolts could crack the wood like a log splitter, Sylvis says; newer jobs use clamp-like bolting instead.

The plywood that lines the cripple wall, which transfers strength from the foundation to the floor, is 3-ply, whereas 5-ply is required in permitted jobs. More concerning, the wall doesn’t fully reach the floor. A nail gun was used to secure the plywood to the framing and the nailheads are recessed, increasing the likelihood that the nails would rip through the wood during a tremor. “It looks like a responsible contractor did it,” Sylvis says. “But that doesn’t mean he did a good job.” Is it enough? I ask. His answer sounds all too familiar: “It’s a lot better than nothing.”

It will cost roughly R50 000 to rebolt the house, so that upgrade remains on our to-do list for now. But in most ways we’ve become well prepared, especially compared with many Californians. When a violent windstorm knocked out power last December, Dan, Otto, and I were in good shape. We had lanterns and headlights, batteries, an adaptor to charge our phones in the car – and Twitter accounts, which proved to be the best way to get information.

While friends’ panicky Facebook posts talked of evacuating to the Valley or West Side beach communities, Dan was uploading cute pics of Otto eating canned ravioli by lantern light. What if the freeways were closed, I wondered. The supermarkets shut down. ATMs out of service. This windstorm was nothing when stacked up against what a big quake could deliver.

“We live in a world that has things we don’t understand very well,” Heaton says. “Does that mean we throw up our hands and just say it’s inevitable, that we’re going to die anyway?” No. It means we design buildings to make them less vulnerable. We prepare our homes and families to ride out calamities. And we take comfort in the fact that by preparing for the worst, we can maximise the chances that when disaster comes we’ll be among those ready to offer help, rather than those who need it.

South Africa: Time for a shake-up?By Anthony Doman
A little after 10 o’clock on the night of 29 September 1969, I stumbled sleepily down the passage wearing my pajamas and what my father tells me was a quizzical look on my face. “I think we’re having an earthquake,” I said. I clearly had a gift for stating the blindingly obvious.

With the ground heaving uncomfortably, the family hot-footed it out to the garden of our home in Wetton, on the Cape Flats. It felt eerie, everyone being outside at that time of night. Lights were flickering on, panic was setting in and uncertainty was everywhere.

And then the earth moved, sickeningly, once more.

But that was nothing compared with just a hundred kilometres to the northeast. Tulbagh, nestled in the Winterhoek mountains, was near the earthquake’s Ceres epicentre. Townsfolk thought the end of the world had arrived as the 6,3-magnitude quake rumbled, roared and sowed devastation – taking a dozen lives and leaving half the town homeless. When the aftershocks had abated, the town was left in ruins and many buildings had to be demolished.

Today, a restored Tulbagh bears few visible scars. And it’s all quiet on the earthquake front… for now.

Africa, fortunately, has not been subjected to the earthquake devastation on the scale seen in parts of the world such as south-east Asia, the US West Coast and Haiti in 2010. The continent’s worst disaster of this sort cost 15 000 lives in Morocco in 1960.

What is the potential right here in South Africa? Depending on whom you believe, we’re in for a really big one… or we could wait a while.

The south-western Cape is a higher-risk area for big earthquakes than the rest of the country. Cape Town – and the Koeberg nuclear power station – lie close to the Milnerton Fault, scene of an estimated 6,3 earthquake in 1809. Seismic activity maps for Southern Africa also show hot spots clustered around Ceres in the Western Cape, Koffiefontein in the Free State, the Witwatersrand and Lesotho. Mines make the Witwatersrand prone to more frequent (but smaller) events. In the past year, tremors measured from 4,0 to 4,3 have been felt in Klerksdorp, the Karoo, Swaziland and the Southern Cape.

The likelihood of a big quake has increased with the spread of the East African Rift fault-lines, says Dr Chris Hartnady of earth sciences consultancy Umvoto Africa. Hartnady has called for greater earthquake awareness and planning so that we can cope better with disasters.

Local building regulations have been beefed up in recent times to ensure quake-resistant construction, particularly in Cape Town. Although South Africa is not regarded as earthquake country according to the Southern African Institute of Steel Construction, the new loading code stipulates that seismic actions need to be taken into account in design much more often than in the past.

That came into sharp focus last year when a 9,0 magnitude earthquake caused a crisis in the area around Japan’s Fukushima nuclear plant. Eskom rushed to allay fears, telling Parliament that Koeberg’s design was more advanced and safer than the Japanese plant’s and could withstand a 7,0-magnitude seismic shock.

Then again, a 2010 analysis by risk management specialists Aon Benfield and the University of Pretoria into potentially the country’s biggest financial loss says that South Africa’s big earthquakes occur infrequently. Their report, South Africa Spotlight on Earthquake, says it helps set the record straight regarding hype around predictions of a Haiti-scale scenario for Cape Town and Durban.

The report analyses selected seismic events that occurred between 1620 and 2006 within a 300 km radius from Milnerton. It concludes that an earthquake of magnitude 6,0 up to a maximum of 6,87 can be expected to occur once in 300 years in the Cape Town area. The resultant damage in the Cape Town CBD would be categorised “ruinous”.

Although a magnitude 6,3 quake occurred in the 1930s at St Lucia, about 220 km north of Durban, South Africa’s largest port city is at no great risk. The likelihood of even a magnitude 5,0 event causing significant damage is estimated at once every 735 years.

Excessive pressure between tectonic plates can cause them to slip and the ground to rupture. A series of seismic waves emanate from this hypocentre (as opposed to the epicentre, the point directly above that on the surface). Fast-moving primary, or P-waves, reach seismograph stations first, and like lightning preceding thunder, can provide valuable seconds of warning before the real shaking begins. P-waves cause rock to expand and contract as they pass through it. Secondary shear, or S-waves, displace material at right angles to their path and reach the surface later. They undulate along Earth’s crust much like ocean waves and, as a result, they cause the most damage.

Improve your earthquake IQ
Building regulations were not always so rigorous, especially in earthquake-prone areas. Here’s how to eyeball the risk posed by various structures.

A skyscraper’s credentials aren’t visible from the sidewalk, but you can rest assured that steel is more pliable than brick or concrete, and that modern skyscrapers are subject to stringent seismic standards. “You don’t just want to build something that’s stronger; you want to be able to control where it gives,” engineer Aaron Reynolds says. To do that, architects add “dog bones” to the frame; areas of reduced width on the building’s steel beams. These weak zones absorb shaking, diverting strain from its welded joints. If you’re inside a high-rise during a quake, stay put; you run a greater risk of being hit by debris outside.

One of the safest places to be during an earthquake is inside a well made wood-framed home. Metal connectors join the floors and walls in newer houses; older ones have often been professionally retrofitted or bolted. This creates what’s called a continuous load path, in which the frame of the house moves as a single unit during tremors. Hardware should also connect the foundation and mudsill to wall studs.

Intense shaking can cause old masonry walls to crack, crumble and collapse. Brick buildings can be strengthened with concrete and have steel “moment frames” installed around storefronts. Often, steel wall-to- floor reinforcements are visible from the street, where sandwich-sized metal plates delineate the line between storeys. While such retrofitting work is often mandated by building regulations, there are still old brick buildings with little or no quake reinforcement.

Without sufficient metal rebar, concrete buildings are prone to pancaking. The risk is often higher in a building with a “soft” first storey – one with high ceilings and multiple openings. Though rebar isn’t visible, other reinforcement is: contractors adhere carbon fibre to concrete walls and posts. “It looks like somebody glued on a hessian bag,” Reynolds says. You may also see shear walls bracing the soft first storey.

A building with base isolation rests atop a series of flexible rubber cylinders; these act as a suspension system, turning violent jolts into subtle vibrations. The approach is the gold standard for hospitals, schools and buildings that contain computer servers, refrigerated medical samples and other valuable equipment. Such buildings are usually surrounded by a concrete moat at street level. Look for a tiny gap in the pavement near the building’s exterior walls.

Plan, prepare, survive
Preparing for disaster is on lots of people’s to-do lists. But less than one- fifth of households compile an emergency kit sufficient for a large-scale catastrophe or practise for one. Here are tips for riding out a quake safely.

Before the big one
Furniture: Use wall straps and Prestik to secure valuables and stabilise tall furniture. Head injuries caused by falling objects are a common trauma.

Emergency kit: Companies such as Gerber sell kits, but it’s often cheaper to compile your own. Use a weatherproof container, such as a plastic garbage can, to store supplies, including a battery- or hand- powered radio (some double as cellphone chargers), flashlights, spare batteries, canned food, a manual can opener, first-aid supplies, and plenty of heavy-duty trash bags. Also keep photocopies of vital documents and prescriptions and a few hundred rand in small bills on hand.

Water: Estimate 5 litres per person per day for at least 10 days, and store the water separately from other supplies.

Bedroom: Keep shoes and a torch near the bed. Lacerated feet were the most common injury during California’s Northridge quake. Use closed-loop hooks for framed art and avoid hanging anything heavy above beds.

Kitchen: Use cabinet latches to keep glassware from toppling out and shattering. Avoid storing ammonia, bleach or hazardous supplies on high shelves where they could spill.

Cellphone: If you use Facebook or Twitter, begin following local emergency service agencies now. In recent disasters, social media sites have been the best source of information. Utility room: Use metal straps to secure your hot water heater to the wall. Keep fire extinguishers where they’re easily accessible.

After the big one
Wall phone: Landlines will be more reliable than cell service (though you may get text messages to go through even when calls won’t). All family members should know the number of one out-of-town contact who can relay that everyone is okay.

Utilities: Turn off water, electricity, and – if you smell a leak – gas. Fire is a real danger during the aftermath of an earthquake, when firefighters will likely be overwhelmed with other calls. Put a spanner inside a plastic bag, tape it just above your turnoff valve, and be sure your family knows how to use it. If there’s no evidence of a leak, however, leave the gas on. A functioning stovetop will be helpful if the power remains out for an extended time.

Backup H2O: The typical water heater contains 200 litres of potable water. The water in your toilet cistern is replaced after each flush and is also generally safe to drink. Gone through that? Regular house-hold bleach can make the dirty drinkable. Add 16 drops of bleach to 5 litres of dirty water, strain and sip.

Porta-Potty: Using your backyard as a bathroom will likely get gross fast. Instead, line a bucket or your dry toilet bowl with a heavy-duty trash bag. Add a little cat litter. Go. Repeat. When full, seal the bag and store separately from your other garbage.