Thursday, October 18

Can We Escape the Million-Death Earthquake?


Q

Your book’s subtitle is "The Science of Predicting Earth’s Deadliest Natural Disaster." Yet in the book you refute various ways people have proposed to predict or prevent earthquakes. So what do you mean?

A
Yes, that subtitle uses "prediction" in a very loose way. One of the main themes of the book is, what are earthquakes and how do we study them? The other is, earthquakes are a problem, and so what can we do about them? There is increased risk [from] earthquakes not because earthquakes are becoming more frequent, but because cities are growing bigger and cities are becoming more vulnerable.

Predicting earthquakes in the sense that it’s normally used—saying, well there’s going to be an earthquake in this particular place next month—that sort of approach was something that was thought about 50 years ago to be something that would become routine by the 21st century, and that hasn’t happened. In the sense that it’s used in the book title, it’s really a question of where we might look for places in the world that are particularly at risk from earthquakes and what sorts of solutions can we bring in that will strengthen communities in those vulnerable places.
Q

One of those is California. You mention in the book that some scientists say the fault that caused the great 1906 San Francisco quake, a 7.8, will rupture at about the same magnitude again around the year 2030.

A
Again, that’s not a prediction in the sense that 2030 is going to be the year, but more that there was a period in the late 20th century where we did not see many earthquakes in northern California. And the idea was that maybe the stress that drives major earthquakes was pretty much released in 1906, and it needs a period to build up again, and that period of building up stress may be coming to a close. We may now be seeing a situation where there’s enough energy in the system that we could start getting more increasing earthquakes in northern California, possibly leading to a repeat of the 1906 quake at some point in the next 30 to 50 years.
Q

Since it’s not possible to precisely predict quakes, how did they come up with 2030 in particular?

A
It was done largely by looking at the historical record and extrapolating from that. If you go back and look at Californian earthquakes before 1906, then you see another period where there weren’t very many earthquakes. and they gradually start increasing in number up to 1906. What had been argued is that the pattern is repeating itself, that there has been a long period of no earthquakes throughout the 20th century and then in the very late 20th century you start seeing an increase in numbers again. However, the problem with that is that because a pattern works once it doesn’t necessarily mean it’s going to happen again the same way, so you have to put a lot of uncertainty on that sort of estimate.
Q

You focus partly on building structures and cities to withstand earthquakes. What are some ways to go about doing that?

A
In the case of California, there are all sorts of tricks for making big buildings, bridges, and power stations earthquake-proof, but these are high-tech engineering solutions. You have to be not too idealistic and say, well, here’s a perfect way of building houses that are earthquake-proof; let’s do this everywhere, because engineering methods that are expensive are no use in developing countries where there’s no money to pay for them.

We know that some types of construction are much more secure that others. For example, wooden houses survive much better than brick houses, and good brick houses survive a lot better than mud-brick houses. But if all you’ve got in the place where you live is mud brick, then it’s no good to say you should build all your houses out of wood.

So there’s quite a lot of effort being spent to try to find ways of strengthening houses that can be applied in areas where there aren’t a lot of natural resources. These tend to be the vulnerable communities.
Q

So if you had unlimited resources, what would you do to aid earthquake preparedness?

A
It wouldn’t be possible for me, even if I was the richest person in the world, to [drop] into India and start shaking up the Indian building industry and tell them how to build houses. They’d be a bit resentful of that. You’ve got to make sure different parts of society work together toward this goal of increasing earthquake safety. It’s no good saying, "Here are the guidelines on how to build safe houses" if the building company or the town builder says, "Oh well, I can save some money if I don’t bother following these instructions." It’s not enough to tell the builder what to do. You’ve got to have a government official who’s going to come round and check that he’s doing it. So it’s not something that can be solved by waving a magic wand, I’m afraid, not even one with a very large amount of money attached to the end of it.
Q

You warn of "rogue quakes." What are those?

A
All earthquakes occur on fault lines, but faults are far more common than most people realize. The rocks we live on have been around for a long time. They’ve been broken up in response to episodes of mountain building that happened millions and millions of years ago. So faults are very common.

A "rogue earthquake" occurs on a fault that wasn’t identified as being particularly dangerous. That can happen in areas where earthquakes are very rare. You might get one every several thousands of years, so the last one was long before living memory.

The other sort of case is earthquakes that are a surprise but shouldn’t be a surprise, and that was very much the case with Haiti. The fault line that produced the Haiti earthquake was well-known . . . There was a historical record of a devastating earthquake back in the 18th century. But in that case, a lot of people hadn’t looked into the history of earthquakes in the area and didn’t realize that the fault was as dangerous as it is.
Q

What’s the most interesting thing going on in earthquake research?

A
I think the thing that’s most interesting at the moment, certainly from my point of view, is looking at the patterns of earthquakes and trying to understand how they operate. This goes some way toward preventing the problem of rogue earthquakes that we talked about earlier.

For example, one thing that was not really understood some years ago but is now becoming more and more established is that earthquakes tend to happen in clusters. You can look at a particular area and see a pattern whereby you get a number of strong earthquakes in a relatively short period of time, and there’s a long gap before the next one. So when you’re trying to assess what’s going to be the future in that particular place, it depends rather on whether you are in the middle of a cluster. In that case it’s a short time interval, or if you’ve reached the end of a cluster, it’s going to be a long time before the next one is due.

Whether you can actually take advantage of that is another matter. It would be rather dangerous to say, "I’m out of a cluster now and I don’t have to worry about earthquake," because you might find that you are wrong. But from that sort of observation we might be able to gradually put together a better idea of why earthquakes happen in the patterns that they do. There’s a lot we still don’t understand about the mechanics of earthquakes.

Another thing that has been discovered within the last 20 years or so: When the rocks actually break in an earthquake, it was formerly thought that it was a clean break—you have a fracture that starts and goes from one end of the fault to the other. What we’ve now discovered—and this has only been possible because of much more sensitive monitoring of earthquakes in the past couple of decades—is that even large earthquakes start off as small ones. You get a very small earthquake in the first second or even fraction of a second in which an earthquake happens, and that triggers a slightly bigger earthquake, which triggers a slightly bigger earthquake, and then suddenly the fault goes bang and the whole fault just unzips. What we don’t know at all is why it happens like that and what tells a fault whether it’s about to have a small or a big earthquake. In a way [that] one seismologist put it recently, we know roughly why earthquakes start, but we don’t know why they stop. What is it that stops a small one from growing into a big one in some cases, and why in other cases does it turn into a really big one?

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You can write whatever you want, but technically, the precise mathematical-statistical forecast of earthquakes based on information about the behavior of wild and domestic animals, birds, fish, and individuals available from 1995, with the advent of social networking.

THE STRUCTURE OF INPUT BIG DATA: API applications to social networks