FANS of big, thick black headlines have had a lot to be happy about in the last week or so. First, the stock market threatened to crash, and then the earth in California quaked. That's the most disaster that American newspapers have had to play with since the Challenger explosion. And both of last week's stories included double coverage potential: the business and sports sections, respectively, got to echo the front page.

It's not just newspapers whose lives were made livelier by the presence of jittery activity on both coasts. Television too had a lot to talk about, and so did ordinary people with nothing else to do.

The way Americans respond to disasters and potential disasters is a subject worth dwelling upon. The permanent damage of the stock market's bounciness seems negligible at this point. And while dozens of people were killed in the San Francisco earthquake, and tens of thousands were left homeless, hundreds of millions of people all over the country saw, heard, read or talked about both incidents.

The experiences of those directly involved in the two shakeups were doubtless more wrenching--but the rest of us experienced something too in the last week. We were all there, fascinated, hoping to live through something really big.

REALLY big: numbers played an integral role in both New York and San Francisco. Perhaps academics who complain of America's mathematical illiteracy will be encouraged. A disaster is not worth getting excited about, it seems, until a number has been attached to it.

In the case of the stock market, such a numerical need is perfectly logical. The number was the story: down 190.58 points. The way in which numbers are expected to grow into bigger numbers, however, is not so straightforward. Exciting numbers--200, 300, 400, 500--flitted through American minds all weekend. In the end, a combination of relief and disappointment greeted Monday's actual closing figure: back up 88.12 points.

California's big number was 6.9. But either a Richter scale is too abstract, or the numbers it produces aren't satisfyingly meaty enough. Right from the beginning, Ted Koppel was begging for some casualty counts that he could spread around via ABC.

As was the case with the market, the American imagination counted its chickens in the Bay area before they cracked. Original estimates of "quake dead" (as the New York Times called them) had to be downgraded from 270 to 59. The three-digit figure was appealing to the media, but alas, not true.

WE Americans don't just want to read about something big. We can do that in history books. We want to live through the big event, to experience "history in the making." Two frequently-heard numbers last week were 1906 and 1929. A knowledge of history and of the possibility of being part of history in 1989 has colored our perceptions of both events.

We all know about the great San Francisco earthquake of 1906, and we all know that it's supposed to happen again sometime. The epic aerial shots of the city-on-the-bay that the television networks played throughout last Tuesday evening certainly carried enough historical grandeur to fit into a future documentary on the 20th century. The World Series angle could only help: putting the Series off for more than a week nearly guarantees an historical asterisk, at least. And we were there.

ONE could speculate endlessly about the source of our fascination with catastrophe: it could stem from an intrinsic human penchant for the morbid, from a profound national boredom rooted in suburbanization, from an intense nervousness about what the future holds for those who lived through the profligate America of the 1980s, or from any other number of conditions or some combination thereof.

Such speculation is unlikely to be fruitful. On the other hand, by looking at one specific person's reaction to the two main events, we might figure something out. Let's try President Bush.

His ability to remain optimistic would truly be commendable were optimism itself an object of value. About the stock market, our president said simply, "I'm not worried." Visiting California, Bush did let his emotions get the better of him when he said "Jesus" at the sight of Interstate 880. But he quickly recovered enough to sound presidential in expressing his "genuine appreciation for the way this community is pulling together."

Strange though it may sound, Bush--as President--is really the archetypal American observer of disaster. We aren't totally heartless, yet our sense of adventure lets us forget that what we're cheering on is real. Hence our underlying complacency--as if the whole disaster thing were a replacement for the World Series, and our team had the chance to pull together and score the most runs ever in a single game.

The real World Series is set to resume on Friday. On the other hand, seismologists say the real San Francisco earth-quake is still set for the coming decades. As for the stock market crash--well, the economists don't know. If the real crash ever does come, George Bush may well manage to stay aloof. Most of the rest of us, though, won't be able to afford to cheer it on.