“There are no communities that are prepared for a 30-foot-tall wall of water.”
March 17, 2011
As the devastation of Japan’s earthquake, tsunami and nuclear crisis continue to play out on the other side of the globe, geology professor Tekla Harms and her colleagues in the department have been following the situation with great interest and sympathy. While the Western Massachusetts area will likely never experience as terrible a geologic phenomenon as the one that hit March 11, said Harms, much smaller earthquakes do occur with surprising frequency in the region.
Harms, who primarily studies mountain belts and the interactions of plate boundaries around the world, helped frame the scope of the tragedy to Public Affairs’ Caroline Hanna soon after the earthquake struck. An edited transcript of their conversation follows. (Harms was also featured as an expert in a television segment that ran during the Springfield, Mass.-area ABC News affiliate’s evening broadcast March 11 and on the same station’s Mass Appeal program March 22.)
Could you give me an idea of just how big this particular earthquake was?
It’s as large an earthquake as the earth can make. To put it in perspective, it measured 8.9 on the Richter scale, while the the 2010 Haiti earthquake was 7.0 and the Christchurch, New Zealand, earthquake was 6.3. These kinds of big earthquakes happen from time to time, but not always in such populated areas, so you don’t hear about them as much.
How prepared was Japan for such a large earthquake?
I think Japanese preparedness for the earthquake part of this disaster was very good, and that probably mitigated the amount of damage the country suffered from that event. I don’t mean to minimize this by any means. What I am saying is that Japan understands that the nation is located in an earthquake-prone area, and they’ve enacted many building codes and built structures that are earthquake-safe or earthquake resistant. It’s hard to conceive right now, seeing the news footage and photos from the country, but the devastation could actually have been much worse had they not been so well-prepared for it. The tsunami, of course, was another story.
How does a tsunami operate?
A tsunami is a distinctive kind of ocean wave that’s generated when the ocean floor is suddenly pushed up by a moving plate that causes an earthquake. You can imagine it in any bathtub or any body of water; if you displace the sides of the body of water, it generates a wave. A tsunami wave, though, has a very long wavelength, so it doesn’t look like an ocean wave that you’re used to seeing when you go to the shore on vacation. When it’s out in the ocean, it’s not very tall. In fact, boats probably wouldn’t even know if they rode up one side of the tsunami and down the other. But as this very long wave comes to shore and starts to interact with the bottom of the shallowing ocean, the wavelength gets shorter and the wave gets taller. That’s what makes a tsunami so tall—it starts with a long wavelength, the wavelength compresses and the wave increases in height. Out in the open ocean, tsunamis do travel very fast. But, because the Pacific is very vast, people elsewhere in way of the tsunami—Hawaii, for example—had a good amount of warning about when it would come. A tsunami also loses its energy as it travels farther and farther. That’s why it was so much easier to deal with in Hawaii. It wasn’t as big. But there are no communities that are prepared for a 30-foot tall wall of water.
Was Japan prepared for the tsunami?
Japan is very well prepared for earthquakes, because planners there know and recognize what kind of geologic area they live in. They also have tsunami warning systems. The problem was that this earthquake was so close to Japan and the distance traveled by the wave was very small. So they really had very little time to warn the people about the tsunami. Also, the water still had most of its energy, because it hadn’t traveled very far. It was a very powerful wave. It washed forward for minutes—10, 15 minutes—and then started to wash back. It drove itself inland very, very far.
How does the devastation from this earthquake, with its tsunami, compare to others?
The tsunami associated with the great Indonesian earthquake of 2004 was quite devastating too. The circumstances were similar—the earthquake came onshore and into Indonesia without much warning. How far inland a tsunami washes depends on how steep the topography is of the nation it affects. In both Indonesia and Japan, the low-lying coastal areas were extremely hard hit. There was a local tsunami associated with the Chilean earthquake a year ago, and much of the damage from that earthquake was due to the tsunami. Like Japan, Chile understands that they live in an earthquake-prone area, and they had taken precautions in terms of building structures and styles, so the tsunami was more devastating than the earthquake.
Should regions or countries on major plate boundaries invest more money in becoming more earthquake prepared?
Earthquake preparedness is, for many countries, an economic luxury. It was not a luxury that Haiti had, for example. The degree of devastation in Haiti reflects that country’s lack of earthquake preparedness in terms of the construction style of the buildings there and their infrastructure. We who live in relatively economically stable and prosperous countries should recognize that this is a benefit of living here. Earthquake and disaster preparedness is not a global fact.
Is there a chance that Amherst could ever experience such an earthquake?
We don’t live on a plate boundary in Massachusetts, but there have been earthquakes here recently and there will probably be more in the future. Experts think some of them are associated with filling the Quabbin reservoir—the earth’s crust is still adjusting to the addition of the weight of the water there 80 years ago. But they are relatively modest earthquakes. There was one in Boston in Colonial times that was quite large and we still don’t really understand why that happened.
It feels like we’ve experienced several major earthquakes in a very short period of time. Is the planet’s topography shifting significantly, or does it just feel that way because of increased media coverage of such tragedies?
The earth has a sort of global energy “budget” fueled by the internal heat of the earth. Much of that energy is dissipated through plate motion, which drives earthquakes. So the amount of energy generating earthquakes is pretty constant over both human and geologic time scales. But how that total energy is partitioned between one earthquake or another, or how it moves one plate boundary versus another can be variable over space and time. So, yes, we have seen a number of notable earthquakes in a short span of time, which have struck in very populated and newsworthy places. At the same time, no, nothing fundamental about how the earth works is changing.
Will ever be a way of predicting earthquakes?
There are two ways of looking at this question. The first is whether or not we will be able to predict that an earthquake is imminent, in a time frame that would allow for evacuations. This depends on earthquakes having predictable, systematic behavior. The more we study earthquakes the less likely this seems.
But we can “predict” with 100 percent certainty that Japan, California, Haiti and similar locations—because they lie on plate boundaries—will experience earthquakes, both small and devastatingly large. Armed with that knowledge, governments and communities can decide to make themselves more earthquake-resistant. Whether or not they do so, unfortunately, depends less on scientific understanding than it does on economics and social policies.