In Touch With Your Inner Seismometer

“Do you feel that? Well, do you?” the woman demanded of her friend as the two sat, watching their children, inside a stuffy Red Cross post-earthquake shelter in San Fernando Tuesday afternoon.

“I feel all the aftershocks,” the woman said, somewhat proudly, as her silent friend looked at the floor and strained to see the aftershock that she obviously wasn’t feeling.

The truth is, you may indeed feel dozens of aftershocks from Monday’s 6.6 Northridge earthquake.

And you may imagine a great many others.

Experts have no simple explanation for why people seem to feel a sense of imbalance long after the earthquakes and aftershocks are over. For some, the sensation is similar to seasickness. Others think they are feeling tremors when even the seismometers at Caltech are quiet.

One guess may be that people are more sensitive to movement after an earthquake. For example, maybe you never realized before just how your house vibrates when your three children and five neighborhood kids charge through it after school, slamming doors and banging walls.

“After a big experience, it really tunes you in to small movement,” says Dr. Clough Shelton, a neurotologist at the House Ear Institute in Los Angeles.

Clough says he knows of no inner-ear disturbance or physiological reason people would feel shaking after the quakes have stopped.

There is a nice French phrase-- mal debarquement --for the sensation people often experience when they disembark from a boat but still feel like they’re riding the waves.

But this isn’t that, Shelton says.

“ Mal debarquement is from a persistent, rhythmic stimulation of the inner ear. It’s a hallucination of motion when no motion is present,” he says. “But an earthquake is so irregular and so short, I think it’s more that people are just more tuned-in to small movement.”

The sensation may indeed be psychological, says Robert Butterworth, a Los Angeles psychologist who spent Tuesday counseling traumatized victims of the earthquake at Red Cross shelters.

“I’m sure we are being hyper-vigilant,” he says. “We have developed this little probe--it’s like another sense--and it’s sensitive to any kind of earth movement. Now that we have that sense awakened, it may stay ‘on’ for a little while longer.”

Dr. Peter Swerdlick, a Sherman Oaks psychiatrist says he believes the sensation comes from memory; people are simply re-experiencing the shaking feeling through their memories.

“This experience is now stored permanently in our memory banks,” he says. “Anything in the future that produces unsteadiness in any situation is going to reproduce, in many people, the feeling of tremendous fear and anxiety and trigger a flashback. People can actually feel the sensation again. It reopens the memory bank.”