Microkhan by Brendan I. Koerner

The Terrible Predictability of It All

January 13th, 2010 · 5 Comments

One of the most ghoulish-yet-wise sayings we’ve ever heard is “Earthquakes don’t kill people, buildings do.” (Or, a bit more accurately, poorly constructed buildings do.”) So as soon as we heard news of Haiti’s latest natural catastrophe yesterday, we knew the death toll would be high. There is little chance that the nation’s relatively weak government has made the enforcement of building codes a top priority, and poverty has doubtless compelled most builders to resort to the cheapest, least stable materials imaginable—notably reinforced concrete, or bricks held together by inferior mortar. To our knowledge, there is no low-cost alternative to these materials that can be easily subbed into building projects in the developing world. The only real solution remains widescale retrofitting with steel or iron bars, a project far too complex and expensive for the destitute Haitis of the world.

What strikes us as particularly sad is how seismologists have turned fatality prediction into a relatively simple formula, based primarily the material composition of a nation’s building stock. As the map above shows, the United States Geological Survey has developed a model for estimating just how many souls will perish in a given country should an earthquake of a certain magnitude occur. The vast discrepany between the Western and Eastern Hemisphere is solely due to the latter’s greater reliance on concrete and brick. This observation really jumped out at us:

It is evident from large deadly historical earthquakes that the distribution of vulnerable structures and their occupancy level during an earthquake control the severity of human losses. For example, though the number of strong earthquakes in California is comparable to that of Iran, the total earthquake-related casualties in California during the last 100 years are dramatically lower than the casualties from several individual Iranian earthquakes. The relatively low casualties count in California is attributed mainly to the fact that more than 90 percent of the building stock in California is made of wood and is designed to withstand moderate to large earthquakes. In contrast, the 80 percent adobe and or non-engineered masonry building stock with poor lateral load resisting systems in Iran succumbs even for moderate levels of ground shaking. Consequently, the heavy death toll for the 2003 Bam, Iran earthquake, which claimed 31,828 lives, is directly attributable to such poorly resistant construction, and future events will produce comparable losses unless practices change.

A Nobel Prize certainly awaits the man or woman who can come up with a low-cost building material capable of mimicking timber’s strength. Though, as always, innovating is only half the battle—the tougher part is convincing scores of nations to make the switch. And for that to be the case, the material has to beat reinforced concrete on price. We fear we’re years away from such an R&D achievement.

Update It probably bears adding that we remain deeply skeptical of mankind’s ability to predict earthquakes, at least in the next 30 to 40 years. However, we did write a 2004 Wired piece about one ongoing effort to “create a model that predicts not only the timing of earthquakes, but also the severity.”


Tags: ······

5 Comments so far ↓

  • Captured Shadow

    I was amazed at the amount of steel I saw going into 3 and 4 story buildings in Japan. They are serious about earthquake codes there.
    The problem with cheap concrete or masonry construction is that is only strong in compression loading. It doesn’t take much tension to pull apart a brick, but it takes a heavy load to crush it. I think these guys at Berkeley are on the right track, trying to add a cheap local material (burlap bags) that can support a bit of the tension load. http://www.engineering4theworld.org/adobe.html
    I have seen bamboo used too, and it can add a lot of strength. I hope Haiti uses these tricks as it rebuilds, but often the materials shortages are worse after these kinds of disasters, so even worse buildings go up.
    Sadly, no mater how strong the building, there is an even bigger earthquake lurking.

  • Brendan I. Koerner

    Wow, thanks a mil for the link to the burlap project–so imaginative, and apparently effective to some extent (though it’s tough to know whether “225 percent stronger” translates into any meaningful earthquake resistance).

    The scale of the rebuilding effort will be a huge impediment to these sorts of solutions, though–unless a central body takes charge early on, with some coherent plan in mind. But that will be a tall order for a nation struggling as mightily as Haiti.

  • scottstev

    The logic is awful and circular. Weak gov’t and poverty help create buildings that cause extensive casualties in the countries that are least able to respond to disasters on that scale.

    In times like this, practitioners of theodicy really have their work cut out for them.

  • Link Blogging « The Daily Seyahatname

    [...] “The Terrible Predictability of It All.”-Microkhan [...]

  • Degrees of Fragility | Microkhan by Brendan I. Koerner

    [...] would have been much, much worse had the nation not committed long ago to sound engineering. As previously discussed on Microkhan, it is disturbingly easy to predict an earthquake’s death toll based on both the magnitude of [...]

Leave a Comment