Not to be too dramatic, but this is a very, very likely headline at some point. At any point really. A lot of the talk in Tehran is about earthquakes. Why is it such a subject? And is it just scaremongering and negative attitude?
Well, after a bit of research I can tell you the story is actually pretty grim. For a concatenation of reasons that will make your head spin, when (not ‘if’) a large quake of, say, 7, on the Richter Scale, hits Tehran, the city and a huge number of its population are pretty much doomed and the risk of a quake of this size for Tehran is extremely high.
Let me depart for a second on a useful aside to explain a little the sometimes-misunderstood Richter Scale. The Richter scale, designed by a clever fellow named Richter, measures the strength or intensity of the shock waves produced by an earthquake. The scale is measured in steps from one upward. Importantly, each successive unit is ten times more powerful than the one before. Therefore an earthquake that measures 7.0 on the Richter scale is 1000 times more powerful than an earthquake measuring 4.0. Remember throughout this blog article that the difference in ground effect between a 7 and a 7.1 on this scale is nothing short of gob-smacking. And an 8 simply is apocalyptic.
So, why is Iran, and Tehran in particular, such a risk?
The first reason for the high risk is Tehran’s location, perched between no less than three major fault-lines, and surrounding, and undercut by, at least a further 100 fractures (a little fault line, as best my lay-person’s inquiry reveals). And these are just the ones known.
The largest of these fault lines, the Mosha, the Tehran, and the Rey, are each on their own enough to bring down a city if they get active. The proximity of these faults, and all the fractures, to each other is the problem; if one goes, they all likely do. If one of the big fault line quakes, the fractures act like, so I understand, the folds of an accordion, flapping madly.
Figure 1: Map of Tehran’s faults
The second reason for the high risk is the nature of the ground on which Tehran is built. Tehran is built largely on sediment (http://atlas.tehran.ir/Default.aspx?tabid=241). The ground conditions in many parts of Tehran are unfavourable: too soft, too brittle and too dangerous, to build on. But building, and building rapidly, is exactly what is happening as Tehran has expanded
Additionally, this sediment under Tehran serves to hide fault lines. There is a strong risk that further faults and fractures exist under Tehran’s sediment which are not known.
The third reason for the high risk is man-made. The structure of the city and its construction does nothing to mitigate the risks. A source quoted by Reuters in 2003, a professor of geophysics at Tehran University and a government adviser, said a quake as strong as the one that flattened the southeastern city of Bam could kill millions, in large part because building codes are almost universally ignored in Iran and rules for earthquake proofing are ignored. This means, with the increase in high-rise living in northern Tehran, on the slopes of the north Tehran fault, building topple, and building rub (where building share walls and rub against each other during the quake), will serve to bring down everything else around.
So, against this backdrop, when thinking Tehran, one must also think earthquakes; they are a part of the furniture. Tehran has suffered more than 1000 earthquakes measuring between 0 and 5 on the Richter Scale, and Iran more broadly has 3-4 quakes (although sometimes as many as 20 or more!) every single day. In the time it took me to write this article this morning, ten earthquakes ranging from 1.3 to 4 on the Richter Scale were recorded in Iran.
Figure 2: Map of earthquake activity across Iran
Iran suffers big quakes (larger than 5) at a rate of about 20 per century. While there is recorded seismic activity every day in Tehran it is, however, more than 150 years since Tehran was hit by a large quake. It has been hit by quakes as large as 7.7, for instance way back in the year 958. More recently, in 1830, Tehran was hit by a size 7, and 43,000 people were killed. The relatively low death toll in 1830 can be attributed to the city being very small then, everyone living on the ground floor, and mostly everyone lived on the flat lowlands below the mountain range. Now, however, the population of Tehran is enormous, a great number of that population live on the edge, or on, the mountains in question. And the overwhelming majority of residents live in high rise, of which, building standards are, at best, questionable.
So, with the rate of big quakes across Iran, and periodically for Tehran, the capital is overdue on average expectancy by about 20 or 30 years for its next big quake of between 7 and 8 on the Richter Scale.
There is no sugar-coating this.
If a quake the size of the one that struck Tehran in 1830 were to hit Tehran today, at least 6% of the population of Tehran would be killed in the initial quake. That’s nearly a million people. This would take Tehran straight into the top 3 most deadly natural disasters in history (behind the 1931 China floods and the Yellow River flood of 1987). Many more are projected to die afterwards as a quake that size is estimated to raze 80% of the city, rendering the city immediately unlivable for those who survive the quake and its aftershocks. Help might also be tough to come by for those many millions; a survey in the mid-2000s found that less than 20% of the city’s emergency service buildings were of good earthquake standard, so the fire brigade might not be showing up anytime soon.
If the quake was a 7.7, as hit in 1830, we are looking at several millions of deaths and a razed city, and Tehran would then be straight to the top of the world’s deadliest natural disasters. And, for me at least, it is very hard to contemplate that.
Iranian experts were asked by the Government what to do about the earthquake risk in the capital. The answer? The only way to avoid a massive quake killing millions in Tehran is to move the capital.
In 2010, the government of Iran announced that “for security and administrative reasons” the plan to move the capital from Tehran had been finalized. Shahroud, Esfahan and Semnan were each named as three of main candidates to replace Tehran as the capital.
It is not all doom and gloom of course. Firstly, it has not happened yet. And it won’t happen while I am here, surely. And secondly, if it was not for this seismic activity, Tehran would not have magnificent mountains that are its immediate northern backdrop, with very agreeable skiing on the doorstep.
But skiing or no skiing, as I predicted at the outset, the situation is pretty grim and hard to find an up-side. It is unfortunately only a matter of time before our headline rings true.
The best thing to do if you live in, or will live in, Tehran is to be prepared and take note of the following advice:
- Fasten shelves securely to walls, and place heavy objects on lower shelves.
- Store breakable items in low, closed cabinets.
- Hang items such as pictures and mirrors away from beds and anywhere people sit.
- Brace hanging light fixtures.
- Repair known defective electrical wiring and gas connections.
- Strap your water heater to studs in the wall and bolt it to the floor.
- Repair any large existing cracks in walls or foundations.
- Store poisons such as pesticides and herbicides, as well as flammable liquids, on bottoms shelves of latched cabinets.
- Identify safe places in each room (safest place is next to furniture that causes a ‘cavity’ if something drops on top of it, like a sofa, preferably against inside walls, away from glass).
- Locate safe places outdoors (away from buildings, trees, electrical lines, and bridges).
- Teach family members how to turn off gas, electricity, and water.
- Have disaster supplies on hand (flashlight and extra batteries, battery operated radio, fist aid kit with manual, emergency food and drinking water, non electric can opener, cash, sturdy shoes).
- Develop an emergency communications plan in case family members are separated.
- Consider purchasing Personal Locator Beacons (PLBs) for each family member.
P.S.: A post-script from a very well-regarded international expert: the sediment grounds of Tehran are even more dangerous than the immediate rocky vicinity of the fault lines themselves. In the event of earthquake, the sands become practically fluid and heavy items such as high-rise buildings fall or even sink! The sands show a reaction similar to pudding (without the fun); even well after the earthquake shakes have already stopped, the “pudding” keeps on shaking and prolongs the devastating movements for much longer.
UPDATE: 17 August 2015: I returned from summer vacation to find a cracked kitchen counter, pool leaks (albeit possibly from old equipment), and windows and doors jammed/misshapen. What is called an earthquake swarm – albeit a small swarm by historical standards – hit Tehran in mid-August 2015. While mostly quite small, all were centred on the same place, at different depths between 10 ann 17 kilometres. Centred on Javad Abad, Tehran, a few kilometres southeast of Imam Khomeini International Aiport (IKIA), the largest at a depth of 14km, measured 4.1 and occurred at 6.42pm on 13 August. One 15 August there were a further two tremors, and on 16 August a further 8 tremors, the largest of which measured 2.8. It is likely the doors and windows were jammed by the 4.1. For the record, in the Tehran region since the start of August, there have been 97 minor separate earthquakes. One should also note for the record also that the shallower the earthquake, the more damaging it is; shallow is bad.