Earthquake hazard mitigation the Iranian way

A post by Chris RowanThe Guardian reports that the Iranian government has approved plans for a new capital city. It seems this decision was at least partially driven by fears that the present capital, Tehran, is facing some serious earthquake hazard in the future:

Plans for a new capital were first drawn up 20 years ago, but officials only gave them serious consideration after the 2003 earthquake that devastated the south-eastern city of Bam and killed an estimated 40,000 people. Experts warn that Tehran sits on at least 100 faultlines – including one nearly 60 miles long – and that many of its buildings would not survive a major quake.

Iran is part of the Alpine-Himalyan Belt, formed as the African, Arabian and Indo-Australian plates all push northwards into Eurasia. In Iran, seismicity is concentrated in the Zagros mountains in the south and the Alborz mountains in the North, with both of these mountain belts apparently being actively uplifted as they accommodate plate convergence.

iran_sesimicity.png

Tehran, with a population of about 12 million people, is located just on the southern edge of the Alborz mountains, and a map of the major faults in the area shows that it is surrounded on all sides by sizeable thrust faults.

Tehran_Faults.png

So, at first glance a relocation seems like a fairly foresighted strategy, even if a cynic (who, me?) might wonder if the move encompasses more than the political elite and their associated minions. But population centres do not generally spring up at random; there are usually strategic and/or economic reasons that people have settled in a particular location, and once established they tend to suck in ever more people and investment as time goes on. Add to that our general inertia in the face of abstract future risk (just look at the response to climate change) and you have to wonder if people will be all that willing to move. There’s also the question of how the cost of abandoning all the infrastructure incorporated into a large city like Tehran, and building a whole new infrastructure in your new city, compares to the cost of increasing peoples’ safety by enforcing robust building codes: after all, earthquakes don’t kill people, collapsing buildings do*.
In the long term, of course, it makes sense to move as much of your population as possible from areas of high seismic risk to low risk areas, by encouraging investment in geologically safer areas and letting economic migration rebalance the population over a generation or three. Sadly, I suspect urban planning is generally driven by somewhat narrower, short-term factors; if building houses on flood plains is waved through without blinking, I can’t see nearby faults giving people much pause.
*and tsunamis. But not in Tehran.
Categories: earthquakes, geohazards, tectonics
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Comments (8)

  1. I immediately thought of Myanmar, where the ruling generals secretly built a new capital off limits to foreigners and most Myanmar residents. There’s a New York times article that describes the place. Having just spent a few minutes skimming Google Earth, I honestly wonder where the Iranians would attempt to relocate 12 million people that is less seismically risky and still hospitable.

  2. Eric Lund says:

    there are usually strategic and/or economic reasons that people have settled in a particular location
    In the case of a country like Iran, availability of water would have to be a major factor. The area around and north of the Alborz Mountains gets sufficient precipitation to support a big city like Tehran. Most other places in Iran do not. So they are better off retrofitting or replacing buildings in Tehran.
    How many capital cities have been built from scratch in recent times, and how successful have they been? Washington DC didn’t take off until air conditioning became widely available, and it’s never been a commercial center. Brasilia has grown to over a million people, but it’s in a country with a dozen or so cities that size or larger, and São Paulo remains the commercial capital. There is the Myanmar example that Anne referred to. The government of the Ivory Coast tried moving the capital from Abidjan to someplace inland, but Abidjan remains the commercial capital. Most large capital cities have had several centuries to evolve to their present state.

  3. Chris Rowan says:

    availability of water would have to be a major factor. The area around and north of the Alborz Mountains gets sufficient precipitation to support a big city like Tehran.
    I vaguely remember being told that in fact a lot of drinking water in this region comes from springs associated with faulting…

  4. Lab Lemming says:

    I’ll leave details of fault controlled springs to your co-blogger, but in a more big picture view, the uplift associated with faults creates the high elevations that can generate orographic snowfall. In areas where this is the dominant form of precipitation, stable, low-lying basins will generally be dry by default.

  5. Lab Lemming says:

    And in an attempt to show just how big the internet is, here’s a travel report on Iranian snowboarding:
    http://www.snowsphere.com/iran/grinding-the-axis-of-evil-snowboarding-iran

  6. A quick google scholar search didn’t reveal anything about fault-controlled springs in Iran, but I wouldn’t be at all surprised. There was an interesting study last winter in Geology on fault springs causing flooding in China…maybe I’ll finally get around to blogging it.

  7. Even if a the technicalities (water, location, willingness, money, …) were fulfilled for the new location, I would be very afraid to entirely move a city. Creating a new one might be fine, but trying to empty the old city from its population (at least the well-off part) will create a power vacuum that will be filled by the kinds of people that will make many futuristic action movies look pale.

  8. Veltyen says:

    http://en.wikipedia.org/wiki/Canberra
    The example is a hundred years old. But a capital city created from near scratch it certainly is. On the other hand it wasn’t moved – the two capital cities that were the other option at the time still exist.