China's Earthquake: What If We Had Known?

On Monday, May 12, the Sichuan region of China was devastated by one of the worst earthquakes in recent memory. At this writing, the death toll stands at over 50,000, and more bad news about the disaster arrives daily. One of the strangest news stories that has come out of region concerns rumors spread on the Internet that scientists working for the Chinese government knew the earthquake was going to happen, and suppressed the information out of fear that making their prediction public would cause panic ahead of the Olympic games.

A news source almost certainly affiliated with the Chinese government (China Radio International) issued a release Wednesday which quoted Zhang Guomin, a research fellow at China's Institute for Earthquake Science, as saying that earthquake forecasts should be based on scientific analysis and not tailored to political requirements. According to him, earthquake forecasts are not possible with our present state of knowledge. However, another researcher, Zhang Xiaodong of the China Earthquake Networks Center, seems to wish that predictions were possible, because he told the reporters, "I feel deeply regretful and sorrowful at the failure to predict the earthquake."

What if we could predict earthquakes with the same accuracy as, say, we can predict tornadoes today? At least one leading authority believes that such predictions may be possible. A NASA researcher named Friedemann Freund has published a series of papers over the years that connect measurable changes in the earth's electromagnetic fields to strong earthquakes that happen shortly after the changes. (My blogs of Feb. 20, 2007 and Apr. 13, 2006 describe more technical details.)

Without taking sides on whether this is in fact possible, let's do a little thought experiment. Suppose after X years of research and development, we assemble the expertise, equipment, and networks needed to predict major deadly earthquakes. Now no prediction system is going to be perfect, so let's say its accuracy can be quantified this way: when the system predicts an earthquake of at least a given magnitude in a given geographic area during a given time window (probably at least a week, and maybe much longer), the prediction is borne out 80% of the time. And let's say false positives and false negatives are equally likely. That is, for the 20% of predictions that come out wrong, 10% are major earthquakes that happen when none was predicted, and 10% are non-events that don't happen when an earthquake was predicted.

Given this imaginary system, what do we do with it? Do we treat the forecasts like hurricane forecasts and order mass evacuations? That's certainly one approach. Originally, Hurricane Katrina was predicted to hit the Houston area, and a graduate student I knew was pretty perturbed when he wasn't able to arrange for transportation out of the city. As it turned out, he was one of the lucky ones—nothing too bad happened to Houston, but everybody who tried to flee had to endure the grandaddy of all traffic jams on the already-clogged Houston freeways.

Hurricanes generally end up somewhere, so hurricane forecasters are given the benefit of the doubt when they miss on exact predictions of the storm's path. But what if earthquake experts made a prediction that turned out to be a complete bust—that is, everybody evacuates for the full term of the warning and exactly nothing happens? That might sully the reputation of the field indefinitely, and nobody would take them seriously forever after.

To bring the matter closer to home, what if this hypothetical system predicted The Big One for the San Francisco Bay area? If we shut down everything that goes on in Silicon Valley for a week, that would constitute a major economic disaster of its own. You don't just walk up to a huge semiconductor plant and turn off the switch, unless you want to turn it into scrap. Of course, a major earthquake might do that for you, but then you get into the question of how to deal with an evacuation order that would cost billions of dollars to a private company. Lives are more valuable than property, but property isn't negligible. And that's just one example of many problems that we would face in dealing with accurate earthquake forecasts.

The approach California has taken in the absence of reliable earthquake predictions is to mandate earthquake-resistant construction. But that costs more than ordinary construction, and requires a well-functioning regulatory system and a cooperative construction industry, neither of which are always found in other countries. Mass evacuations are simpler, and might be the best path to pursue for countries that can't afford to replace their entire infrastructure with earthquake-resistant structures.

Clearly, even if we had reliable earthquake prediction, we would face a lot of issues in deciding how to act on the knowledge it would provide. But it seems to me that knowledge is always better than ignorance, especially when it comes to earthquakes. And considering the terrible loss of life and property that major earthquakes usually cause, I wish that we spent more intellectual capital on serious efforts to predict earthquakes, and tried to evaluate the predictions in a statistically meaningful way.

Sources: The China Radio International article I quoted appeared at http://english.cri.cn/2946/2008/05/15/48@357631.htm.