PBS Revisits Northridge, Kobe Quakes

“The Day the Earth Shook,” airing on PBS’ “Nova” series tonight, is a compelling analysis of the lessons of the 1994 Northridge and the 1995 Kobe earthquakes, which happen to have occurred on the 17th of January exactly one year apart.

One of the points made is that Los Angeles was lucky. More than half of the energy loosed by the shaking in the smaller Northridge quake was dissipated in the sparsely populated Santa Susana Mountains, while the strongest shaking in the Kobe temblor took place in the thickly populated downtown area.

In Kobe, 5,400 died, while in Northridge, according to figures updated after this program was put together, 72 died. Different building standards accounted for some of the variance, but by any comparison the Kobe quake was more focused where great numbers of people were.

The basic premise of the program is that advances in technology provide the means to prevent damage and loss of life in future urban earthquakes. “The means are available,” the program concludes. “But the systems are not yet in place, either in California or Japan. A catastrophe like Kobe is waiting to happen again. It could be avoided.”

This is an entertaining show. There are wonderful videos of the actual shaking and fine rescue scenes. A half-dozen of California’s most eminent earthquake experts explain the latest means of measuring what happens in such events and, under the best circumstances, of conveying warnings to areas not yet shaken with enough seconds to spare to allow people to take cover, trains to stop or gas lines to be shut off.

But the premise that Kobes or Northridges are avoidable may be too optimistic. “Avoid,” commented Caltech seismologist Egill Hauksson when told about it, is too strong a word. “Mitigate,” he thought, would have been a better one. A big quake is going to do damage and cost some lives, particularly bearing in mind there are bound to be quakes bigger than either of these.

So when the authors of the program ask, “Does an earthquake have to be a disaster?” and seem to answer “no,” some skepticism would seem to be in order.

Still, there are fascinating showings here of devices that may reduce the loss. Particularly intriguing is Barbara Romanowicz, director of the UC Berkeley Seismographic Station, displaying elaborate new instruments to analyze shaking, and touting tiny accelerometers, similar to those that trigger air bags in cars, for use to shut off gas in homes and businesses.

It is particularly difficult to avoid errors creeping into quake coverage, but here only two are noticed. The narrator states early that the Kobe quake was the same size as Northridge. Actually, at the equivalent of magnitude 6.9 on American scales, Kobe was about twice as powerful as the 6.7 Northridge quake. And Kobe damage is put at $147 billion when, according to yen-dollar conversions at the time of the quake and now, it was closer to $100 billion.

Generally, however, this is a very precise presentation and provides both a good comparison of the two quakes and their diverse effects, as well as a telling summary of the progress of quake mitigation.

The program airs on the eve of the one- and two-year anniversaries. It’s a fitting way to observe them.

* “The Day the Earth Shook” airs on “Nova” at 8 tonight on KCET-TV Channel 28.