It’s a grim toll-20,000 dead, 166,000 injured, over half a million homeless. January’s earthquake was India’s worst ever. It hit the town of Bhuj like a hammer blow. While the government and aid agencies struggle to get the city back on its feet, seismologists like Rebecca Bendick have been pondering why earthquakes are becoming more frequent in India-and why this is the tenth to hit the Kutch peninsula in 200 years. Are we anywhere near predicting the next one? Bendick has just returned from Bhuj where she peered beneath the Earth’s crust into the mantle. Roland Pease asked her if she found any clues.
When did you first hear about the earthquake, and what was your reaction?
I always wake to the morning news. And I remember being half-asleep and hearing the radio come on with news of a magnitude 7.6 earthquake in the state of Gujarat. I had just recently spoken with Roger Bilham, head of my department at Colorado State University, about the Allah Bund earthquake in this same area in 1819. When I got to the office, the atmosphere was like a war room and I left for India three days later.
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Plate tectonics is a well-established theory. Is there much that we don’t know?
Absolutely. There is so much we don’t understand. Even on the simplest level, we don’t know the forces that drive plates and tectonics. Then, plates don’t fit that well. There don’t seem to be straight, perfect boundaries between totally rigid plates. There are whole sheets of unexplained phenomena. The most compelling one to me right now is the Himalayan Tibet system, where India meets Tibet. It seems very hot and very soft underneath Tibet, and it’s hard to find traces of India down there. The logistics of studying this are horrendous. In Nepal, where I’ve been, there’s only one road from Kathmandu to Lhasa in Tibet. You have to travel everywhere on foot. Somebody has got to go out in the middle of nowhere, set up instruments, find electricity to run them and maintain them. That’s why there’s so little data.
What exactly are you investigating on your trip?
The nature of earthquakes means that big events like this recent one happen in any one location probably less than once in a lifetime. And so this is a chance to do science that can’t otherwise be done. Seismology isn’t like other branches of science, where you can design a controlled experiment in a lab. As a seismologist, you have to rely on the Earth to present you with an experimental opportunity. We’re interested in how the entire section of crust and upper mantle responds when a big force is applied. The uppermost layer of the Earth-the crust-seems to behave as though it were brittle. Underneath that brittle layer, the lower crust is ductile and bendable, a bit like toffee. Below that you have the mantle, which acts like a fluid. Earthquakes themselves are just a break in the brittle upper layer, which happens because of what’s happening underneath. When you break the crust, you actually kick the upper mantle and the lower crust. So to understand more about those lower parts of the Earth, we want to see how they respond to that big kick.
Have there been any previous opportunities to study this so cleanly?
Not really. That’s because the majority of earthquakes happen on plate boundaries, rather than within plates themselves. The Gujarat earthquake is a rare example of what is called an intra-plate earthquake (see “Collision course”). The number of great intra-plate earthquakes can be counted on two hands. This is the first time we have had a chance to look at the physical properties of the crust within a plate, rather than on the edge of a plate where things are more complicated.
You took a lot of sophisticated instruments out there. What will they do?
We’re using the Global Positioning System of satellites to get precise positions of points on the ground. We aim to get an accuracy of 1 millimetre, though we probably won’t do that well. These GPS points are about 20 kilometres apart. We’ll measure them now, and then come back in two years, and then again, and again, for the next 100 years. As the soft stuff underneath relaxes after the big kick from the earthquake, we hope we’ll see these points moving.
How did you first get involved in seismology?
I started my work in science in palaeontology, and that was purely out of an interest in living things and how they interact with their environment. From there, it’s been a long, merry chase. I’ve always been interested in mountain-building because of a personal interest in mountaineering. Right now, I’m interested in where mountains come from-how they evolve and grow and what their shape tells us about the physics of the Earth.
What made you switch to Earth science?
I got into competitive sailing when I was in college and took a course on the dynamics of the atmosphere and the oceans because I thought it would help me win races. After that it was love at first sight. I found it so interesting that I sat in on introductory courses in geology.
Do you still race?
I don’t. I live in Colorado. There’s not much water there.
Which mountain systems have you had the opportunity to study?
Lots. The Venezuelan Andes, the Karakoram range in northern India, the Altyn Tagh faults in Xinjiang in western China, and the Himalayan arc. On one field trip-seven months in Asia-I figured that I had walked close to 1100 kilometres. I did wear through three pairs of boots on that trip.
What’s the highest you’ve been?
Just over 7300 metres.
You’ve also trained as a firefighter with the volunteer fire department. What was the motivation for doing that?
I grew up in a strong, small community. But now that I’ve been living in Boulder for five years I would like to be part of a community again. Where we live has a history of very big, catastrophic wildfires. Some 10 or 12 years ago there was a big fire on Sugar Loaf mountain where I live and it destroyed property. But day to day, we mostly deal with car accidents and that sort of thing.
You’ve landed in a disaster zone in Gujarat. How does it really feel to be doing research when everyone around you is trying to save lives?
Throughout this trip we have struggled with this, wondering whether what we are doing is appropriate given the circumstances. No matter how hard we try, we are using resources here that could be used otherwise to help people. We have vehicles, we have drinking water and petrol, and we don’t know if what we are doing is right.
Do you think it can be justified?
I do. I wouldn’t be here otherwise. There’s no doubt that the immediate needs of people are urgent. But we want to understand the Earth better and understand how earthquakes work, fundamentally. Any progress we can make in that direction can only help in the big picture.
So you could argue that what you are doing will save lives at some time in the future. . .
One would hope. But if not save lives, at least encourage people who live in zones with high seismic hazard to build responsibly. Earthquakes don’t happen on a very human timescale. But it’s critical that we can tell people who live in an area if they are at risk of seismicity, what order of magnitude, and what order of recurrence. We could then help them to build their homes and infrastructure accordingly. At the very least, that is something that we can do that justifies this experiment. At the very most, we can figure out what drives intra-plate earthquakes and their relationship to tectonics.
