What We Still Don't Know About Earthquakes

We were having lunch in a local greasy spoon when the first wave of dizziness swept over me. I figured my wife, a nurse, would be alarmed if I told her, so for a moment I kept my mouth shut.

"I feel dizzy," I finally said.

"So do I," she responded.

A potted plant, swinging gently back and forth over our table, offered the strongest clue of what was going on.

"It's an earthquake," I said, profoundly.

The rickety restaurant near our home in Juneau, Alaska, swayed as the ground rolled like waves on a troubled sea, the clear symptom of a distant earthquake. And it seemed to last forever, revealing that this was no minor temblor.

During my years of chasing quakes and their aftershocks in Southern California for the Los Angeles Times, I had felt many temblors, but this one was a dandy.

The quake measured 7.9 and was centered about 400 miles away. It was one of the largest ever recorded on U.S. soil, according to the U.S. Geological Survey, and ripped across central Alaska on Nov. 3 with a jolt that was strong enough to be felt thousands of miles away.

Progress and Pitfalls

It also revealed just how much progress we have made in earthquake engineering. And how much we still don't know about the science of earthquakes.

We know how to design structures to withstand enormous forces. But we still don't know how to figure out when those forces will strike, what triggers the release of all that energy, and in many cases how the ground beneath our feet will perform.

Those are pretty basic questions, and the complete answers are still beyond our reach.

The quake left a 145 mile scar across the landscape and in some areas the land on the opposite sides of the Denali fault moved horizontally by 22 feet — proving wrong scientists who had thought that changes in seismic stresses had left the old fault unable to produce such a major quake.

Alaskan Pipeline Marvel

The nearby trans-Alaska pipeline that carries oil from the Arctic to the Port of Valdez came through the rumble with some damage, but no rupture — proving that the engineers who designed the $8 billion pipeline were right when they claimed it would withstand even a larger quake than the Nov. 3 temblor.

A lot of folks hadn't believed them.

The pipeline is indeed an engineering marvel. The 800-mile-long steel tube crosses three mountain ranges, 800 rivers and streams, and three active faults as it winds its way across a young and dynamic landscape that is still very much a work in progress.

The engineers who designed it knew the pipeline would have to be flexible enough to withstand a large quake, although some now say they didn't think it would have to experience anything as powerful as the 7.9 shaker, which is supposed to happen in that area about once in 600 years.

It is supported by shoes that can slide back and forth on horizontal beams. The design allows for movement of 20 feet horizontally, and 5 feet vertically. During the quake, sections moved nearly 8 feet horizontally, and nearly 3 feet vertically, so it could have handled even more.

Cocksure Engineering

So where does that leave us? Probably a bit too cocky.

We know, for example, that well-engineered structures have saved thousands of lives during recent earthquakes. But we don't know just how safe some of our structures really are.

Engineers say high-rise buildings can be designed to withstand catastrophic quakes, but that concept has never been tested because no modern urban center has been hit with a major quake of, say, magnitude 8.5 since the beginning of the high-rise age. Cities like Tokyo, Los Angeles, San Francisco and Seattle are still waiting to see if the engineers are really right.

The Unknowns: ‘What’ and ‘When?’

We know what causes earthquakes. Quakes are caused by the sudden release of strain that builds up in the giant tectonic plates as they grind against each other while moving around the surface of the earth.

But we don't know specifically what triggers a quake. We do know it isn't the alignment of the planets, or radiation from space, or your grandmother's gout. The trigger probably varies with local conditions.

And nobody knows precisely when the next quake will occur. Instead of predicting quakes, scientists have settled for long-range forecasts.

So no reputable scientist is going to tell you that California's notorious San Andreas Fault is going to rip up that pricey landscape at 2 p.m. on Friday the 13th. The best they can do is say that some part of it is likely to break loose sometime in the next decade or so.

Faulty Timing

But there is some pretty convincing evidence that even those long-range forecasts are built on shaky ground. Most governmental agencies around the Pacific Rim base their engineering requirements on the idea that faults tend to rupture at fairly definable intervals. It's called the "time-predictable recurrence model," but it may well be dead wrong.

Geophysicists at Stanford University have taken a hard look at that concept and concluded that nature really isn't all that tidy when it comes to scheduling earthquakes. Jessica Murray and Paul Segall examined a famous section of the San Andreas Fault that runs through the farming village of Parkfield in central California.

Parkfield is the most instrumented fault zone this side of Tokyo because some decades ago scientists determined that it has ruptured on average once every 22 years since 1857. Since the last quake hit there in 1966, scientists began packing all sorts of gizmos into Parkfield in the mid-1980s. They reckoned that a quake of magnitude 6 should hit there by around 1987.

Most of those instruments are still there, and new experiments are being set up, but guess what? No earthquake. The shaker is way past due, but so far the score is San Andreas 1; scientists 0.

The Known: Unanswered Questions Remain

So where does that leave us? With a lot of questions.

We know we can build strong buildings. But are they strong enough?

We know what causes earthquakes. But are we ever going to be able to say when?

But there is one thing you can bank on. Sometime in the near future, someone in Congress or the federal Administration will try to whittle away at the already feeble budget for earthquake research.

That ought to shake you up.

Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

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