The occasion was a 4.6 seismic event, 3 miles north-northwest of Chatsworth, which is to say, pretty close to where I live. (The U.S. Geological Survey's report on the event is here.) A 4.6 earthquake is a solid earthquake, but even so, not much happened. No deaths, no injuries to speak of, no real property damage. All that happened in my apartment is that an unlit candle, stuffed in a closet, tipped over. But a few days later, a friend of mine (hi, Sarah!) happened to ask me what I thought about our chances of The Big One hitting.
The Big One is a favorite topic amongst Californians, for obvious reasons. As John McPhee details in his wonderful book Assembling California (collected with two other books in the wonderful
Annals of the Former World--and by the way, I think McPhee is an incredible writer, and I would happily read his writing on any subject under the sun), the state of California was put together in pieces over millions of years. (The great central valley, for instance, is a huge hinge--two gigantic slabs of earth at angles, forming a huge V, into which sediment has slowly filled and filled the V and thus created that massive flat plain between two mountain ridges.) You've got the Pacific Plate over here, pushing against the continental plate over here, plus a smaller plate (the Juan de Fuca) to the north, and it's all inherently unstable. Big earthquakes are, in a word, inevitable.But precisely because of my reading of Mr. McPhee, I have a remarkably casual outlook toward The Big One. Yes, it's gonna happen. Will it happen in my lifetime? No, probably not. So I just don't worry about it. This is because of an idea called "deep time."
We could call it geologic time as well. For a geologist, a million years is the smallest unit of time s/he cares about. That's how long it takes for any geologic change to happen. And once you start thinking in terms of deep time, your perspective starts to shift like crazy. Here's an example of why: look at a ruler. At the far left you have the first black marking, the Zero line. If you consider the ruler as a timeline of earth's entire geologic history, the entire span of human history wouldn't get past the Zero line. It's that small.
So if you then consider my individual lifetime against the entire span of human history, well, that's so small it simply doesn't show up on that ruler at all. That's deep time. Which means that yeah, a gigantic earthquake in my neighborhood is inevitable; these faults will one day rupture and California will one day break apart just as it formed, in pieces, separating and then drifting away toward future collisions and reconfigurations. But the chance of the first part of that chain, a major event on the San Andreas fault, happening in my lifetime is so small that I just don't see any point in worrying about it.
Think about it this way: there are no guarantees in life. None. There's no guarantee that the sun will rise in the morning tomorrow--there's only the probability that it will. Based on what we have observed in the past, there is an extremely high probability that in the morning, there it will be, the sun, shining forth as usual. We all go to sleep at night perfectly content that the odds are in our favor on this one. Well, I have the same attitude toward The Big One.
Then again--there was a small earthquake maybe two years ago, when I was at work, in Santa Monica. At the time I happened to be on my lunch break, sitting in the lobby of the building with a book in my hand. I felt the ground jump a little and then looked up--to realize that I was sitting in a glass-roofed extension of the lobby, and that these gigantic panes of glass were shivering above me.
And yeah, I'm not crazy--that made me a little nervous.
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