Many months afterward, when something still woke my son every night and made him afraid to be alone, the counselor who was helping him asked me to come to the end of their hour together and watch. In her office the counselor had a large tray of sand, the shelves beside it filled with miniature figures and houses and cars. My son was 7, but tall enough to reach every item he wanted, and when I entered the office he had already spread across the tray an assortment of pieces that seemed at first to have been flung roughly from the shelves: houses askew, animals toppled to one side, cars half-buried in the sand.

"Here the people were in a house that fell down a cliff," said my son. He did not lift his eyes from the sand tray; he was holding a plastic dinosaur, considering where to place it. "Here a car was stuck and is trying to get out, but it can't. Here a bear is coming toward a place where people live. Here some people were hurt, and this ambulance was coming to rescue them, but the freeway was broken and the ambulance can't go anywhere."

The counselor was quiet and wrote in her note pad. My son set the dinosaur on a sandy bluff. Below the bluff the small houses leaned perilously in the sand, and the dinosaur was positioned so that its claws extended toward their upended roofs. My son looked at me, his face without expression. "It's an earthquake," he said.

Here is how it used to be, before last Oct. 17, if you lived in San Francisco or the suburban cities gamely straddling the path of the San Andreas Fault: you did not think about earthquake. Eastern relatives might ask about earthquake, government dispatches might warn about earthquake, and every spring the local press shuffled out with dutiful reminders of what happened in April 1906; artfully, and with an instinct honed in childhood, you sidestepped them. A state-funded earthquake expert, Richard Eisner, used to go from place to place, delivering lectures about dangers and preparedness, and he learned to recognize the cordial glazed silence that generally enveloped the room. "It was like talking to the brain-dead," Eisner says.

There were two kinds of earthquake, in the imaginations most of us had cultivated, and only one was fit for the self-protective mind to contemplate. The earth was going to shake a little, which would rattle our dinner plates and then be done, or the earth was going to roar apart beneath us and flatten everything so suddenly and thoroughly that what was left would seem a kind of nuclear winter, stripped of anything worth trying to rebuild. In our mythology of fear such a thing could happen only once, and there was no real point in bracing for it; we called it the Big One, on the rare occasions when we were made to talk about it, and anyone who could sustain a conversation about the Big One was either a structural engineer or the sort of person who might plan in detail his own funeral ceremony. Down in the Santa Cruz area, a sales representative named Rick Dentoni was making a business stop last Oct. 17 and grew mildly irritated when his client mentioned the concerns being raised about the earthquake safety of Dentoni's daughter's elementary school. Garbage, Dentoni remembers snorting -- he is 44, born and raised in a suburb just south of San Francisco -- they found some fault less than 11,000 years old, they want to close the school, what a bunch of garbage.

He was driving home, at 5:04, when his car radio went silent. He saw the road before him ripple, the concrete lifting as though someone had leaned down to straighten a carpet runner, and on the dry hills ahead of him a darkness of dust rose up and away as the ground beneath it heaved. His wife was home, their youngest child clutched in one arm as the living room shelves crashed to the carpet where the baby had just been sitting; Laurie Dentoni pushed herself and her son to safety, but the force of the earthquake threw her to her hallway floor, and when it was over and she had gotten outside, she stared at her house windows and watched the aftershocks bend and bow the glass.

There has been no blurring of these stories, the accounts retold again and again in the first frantic efforts to talk our way through the days immediately after the earthquake. Some of us were thrown to the floor and some were not (my son thought his friend had shaken the jungle gym they were climbing), but even the people who scarcely felt the earthquake will describe today in nearly obsessive detail the things they saw and the thoughts that came to them and where they were standing, in the moments of aftermath, when they learned that a length of the Bay Bridge had collapsed. When the local mental health departments' post-earthquake counselors do their work now, they are met, sometimes, by uneasy men and women who do not know how to articulate the problems that made them come for counseling -- anxiety is quite common, the counselors say, or a terrible weight of helplessness, or an inability to cope with the matters of daily life.

"And all I have to do is go, 'Where were you on October 17?' " says Alexandra Charusofsky, a counselor with San Francisco's Afterquake Project. "And then two or three hours later, after they tell you all this emotional stuff that comes up, they go, 'Well. I guess I was affected.' "

Earthquake Dreams It is not that all the wreckage lurks in some recess of the psyche, certainly; 63 people died in the earthquake, almost all of them killed by falling buildings or the Oakland freeway overpass that twisted and smashed to its lower deck, and among the emergency post-earthquake services were counseling programs established solely for the suddenly bereaved. Social service workers went to the Oakland neighborhood where the freeway fell, so that someone might offer psychological help to the men who scrambled up ladders in the darkness and saw what had become of the people trapped inside. Survivors walk today with chronic pain from broken backs and crush injuries; the resilient Marin County woman named Dorothy Otto, whose account of her hours trapped in her concrete-smashed car led off a Washington Post chronicle of the freeway collapse, has seen physicians for her leg pain and counselors for her stomach pain. The stomach pain would strike violently, on Monday mornings, whenever she was supposed to begin driving again for her work as a sales representative.

"Sometimes it was a smell, or a sound -- an electrical, oily smell that was apparently associated with my car battery that had been smashed," Otto says. "One time there was a terrible rumbling noise, apparently caused by a truck. I would get uncontrollably sobby in the car. One day I just pulled over at a Denny's and stuffed pancakes into my mouth until I stopped crying -- and then I made the sales call."

The graceful interior hallways of San Francisco's City Hall are still braced by wood beams, which serves as a grating daily reminder of the slow pace of physical repair.

y grandmother is waiting out the reconstruction of her barricaded Marina district apartment in San Francisco; for most of the year she has lived in a cramped rental studio with a single shelf of propped family photographs, and when I drove her to the Marina last week we slowed the car on Jefferson Street so that both of us could watch the construction trucks back around four-story-high scaffoldings wrapped around cracked and empty apartment buildings. "Look at my street," my grandmother murmured in Spanish, which is the language she usually speaks. "Ay, look at my poor street."

No neighborhood in San Francisco took the earthquake as hard as the Marina, which spreads for blocks around my grandmother's poor street -- the bay lies just to the west, and the buildings are now understood to have stood on soils full of shifting sands. I had talked the day before to a woman named Barbara Miller, who lives across the street from my grandmother; we sat in Miller's living room, where all the high furniture is now bolted to the walls, and the television stands on the floor, and two large boards in the living room have been covered with color photographs of the smashed 1989 remains of nearly everything she had owned. In Barbara Miller's last earthquake dream, which had shoved her out of sleep one night a few weeks before we talked, the earthquake measured 15.0 on the Richter scale and went on for 64 seconds. In the dream she saw the earthquake but did not feel it; she was stuck, alone, watching everything around her collapse, and unable to make it stop.

Improbably, Barbara Miller and I both smiled a little when she told me this earthquake dream; all at once we are so familiar with the argot of earthquake that the shorthand has worked its way into our nightmares. Red-tagged, search and rescue, 8.1 on the Hayward Fault: Last October taught us the working code for buildings too dangerous to enter, or hunts through rubble for a person who might still be drawing breath, or a massive earthquake down the separate East Bay fault system that runs half a mile from my front door.

I tried in my earthquake dreams to make it stop too, and always it was the paralysis that made a nightmare of what was going on: The house was falling, terrorists were about to blow up the airplane, and I stood with a notebook in my hand and no voice to warn the people I saw that they were about to die.

For a while I thought this was reporter business, that I had spent too many hours below the mangled Oakland freeway without being able to climb ladders and help. But I began to see that a lot of us were unnerved less by the earthquake itself than by the surrealistic hours afterward when the television cameras kept sweeping across the flames and the rubble and the stretchers in the moonlight. Inseguro, vulnerable, desequilibrados, a post-earthquake poster in Spanish reads now, translating for San Francisco's large Hispanic community the words that describe expected human reactions to the sudden unleashing of forces we cannot control and can no longer ignore: insecure, vulnerable, off-balance. A San Francisco flight attendant named Lynn Challacombe kept trying to dial 911 in her nightmares, but the lines were always blocked, and then the shaking would come up so fiercely that she would awake and cry out, certain that it must be happening again.

Last winter Challacombe and her husband, Allan Benson, hung a wind chime in their bedroom, so that when earthquake dreams woke them they could listen for the clappers and know right away whether the shaking was imaginary or real. "I gauged my recovery, and Allan did too, by the period of time that went between these dreams," Challacombe said this month, and it was a comforting cushion of weeks that now distanced them from the last one; they were planning, they said, an earthquake party. There are commemorations scheduled this week all up and down the earthquake's reach, most of them using more somber labels than "party": Santa Cruz plans a memorial ceremony, San Francisco plans a memorial ceremony, emergency workers in Chinatown will stage a large-scale earthquake disaster and rescue drill in Chinese.

But Challacombe and Benson have a party in mind, and they would like, she said, to invite some of the people who used to share their apartment building in the Marina. The building is still standing, but under repair; it was red-tagged after the earthquake, and a local newspaper photographer caught a picture of Challacombe and her 8-year-old son out front on the street amid the plastic garbage bags that held everything they were able to pull from the apartment in the 15 minutes allotted to them by building inspectors. They stayed with relatives, in hotels, in an old rental property Benson had owned, and last summer they purchased the house where they now live. It is a pink house, two-story, with a nice picture window onto the street. The neighborhood, no matter how loosely somebody might interpret the map, is the San Francisco Marina.

The Price of 'Paradise' You will be shaking your head about now, and wondering at the impenetrability of the human spirit, but that is because you have not practiced the Tornado Defense. The Tornado Defense has a long history for those of us who grew up along the San Andreas Fault; in its basic form it involves tornadoes and hurricanes, but I heard it at its most elaborate from Eileen Maloney, who works as communications coordinator for San Francisco's office of emergency services. "We don't have tornadoes," Maloney said firmly, with the dismissive shrug that is always meant to accompany the Tornado Defense. "We don't have hurricanes. We don't have tsunamis. Los Angeles goes up in flames every single summer. In the Midwest, people freeze to death every winter. People die of heat stroke every year in Texas."

Maloney also mentioned river valleys that flood regularly and equatorial regions where people contract malaria and get bitten by tsetse flies, but this was clearly on the order of extra credit and somewhat unnecessary, since the Tornado Defense is not the only one we have. There is also the New York Subway Defense, which is a geographical subset of the Predestination Defense. If you moved to New York you'd get mugged on your way to work is the essence of the New York Subway Defense, the point being that stimulating places without predictable natural disasters are probably going to get you anyway.

"The price of living in Paradise" is a much-repeated axiom around here, as if cities with pleasant weather and lovely marine views somehow owed it to the natural balance of things to be mashed to the ground every once in a while. Indeed, up until last October we offered the Tornado Defense with a sort of manic black humor, since in the shadow of the Big One everybody understood that what we were really saying was, 'Well, lots of places have their natural hazards, and ours happens to be the eventual end of life as we know it.'

I think it had genuinely not occurred to us, committed as we were to clapping our hands over our ears whenever people like the earthquake expert Richard Eisner began to speak, that there might be a third possibility -- that a very large earthquake might bring down buildings and cripple transportation and still leave most of us alive. "It's no longer some fantasy of a bureaucrat who's trying to keep his job," Eisner said last week in the crowded Oakland office where his seven-year-old Bay Area Regional Earthquake Preparedness Project has spent the past 12 months handling frenzied requests for information about earthquakes.

"I think what we were not able to do as far as motivation in six years, Mother Nature was able to in 10 seconds," Eisner said, and managed an extremely small laugh. "You listen to your mother."

Eisner himself is not wholly at rest with the memories of what happened last October; the partitions in his office are covered with color photographs of ripped concrete and caved-in buildings, and he said it was three months after the earthquake that he first brought home a local television station's videotape of the ruins. "And I sat down to watch, and my kids started crying, and I started crying," Eisner said. "I think there's a lot of that out there. When I make a presentation, I have to be very cautious not to stir that up."

He does make his presentations, though, and people lean forward and take notes and ask him detailed questions about the best way to strap down a water heater or bolt a house to its foundation. Since last October the notion of "preparedness" has taken on an unfamiliar cachet; the local newspapers and magazines are filled with seismic charts and home-bolting advice, and contractors who brace homes for earthquakes are doing such furious business that one recent article offered advice on the best ways to watch for the charlatans.

It is not clear to anybody how many people are actually doing this, hiring builders to climb around their foundations with plywood braces and expansion bolts, and how many are simply nodding emphatically about what a good idea that will be as soon as the car is paid off and the kitchen flooring replaced and several thousand extra dollars appear in the household budget. When the air grows hot and still in Northern California we talk sometimes about "earthquake weather," but the fact is that earthquakes really are not like hurricanes or deadly winter storms; they give no warning and have no season to remind you that it is time to prepare. The latest U.S. Geological Survey study estimated the probability of a large San Francisco Bay earthquake at 67 percent -- twice as likely to happen as not, the geologists were saying -- sometime within the next 30 years.

"Sometime within the next 30 years" is an invitation to gamble, if the stakes are as big as your house or your workplace or your grandest decisions about the community where you wish to raise your children. Certainly there are people who coped with last October here by fleeing Northern California -- one day-care center director watched Cambodian families hurl their belongings into the street and head out before nightfall for the mid-state city of Fresno. Challacombe and Benson left for a short while too; he is a pilot, so neither needs to live in San Francisco to work, and when they looked for a house to buy they examined homes as far away as Seattle.

"And then every time I'd come back, and I'd fly over the Golden Gate Bridge ... my heart would just stop for a while," Challacombe said. "And I thought, God, this is the most beautiful city in the world, I love this city."

The house they chose sits a block and a half from the buckled apartment building where they used to live, and both of them spoke with the facility of the newly trained about the geology beneath them and the foundation reinforcements they plan to make this fall. The house was small, they said. If it fell, it would not fall very far. "This building can sink," Benson said, "but it can't fall over into the street and threaten our lives. The worst thing that can happen is we'll take a financial loss, but it's not life-threatening."

That is the complicated calculus that last October left behind: The unimaginable is now the stuff of financial figuring and engineering reports and visual images of something that might look like apocalypse but turns out, on closer examination, to be a collapsed freeway. A young housing activist was hurrying this week to finish work on a half-hour videotape that replayed some of the most memorable footage from last October; the videotape is to be translated into Cantonese, Mandarin, Spanish, and Russian, and in it elderly and disabled people will gaze into the camera and discuss the hazards of major earthquake and the most important things to do immediately afterward.

She was still working on obtaining rights to the song for the closing credits, the activist said; what she wanted was the Grateful Dead. The song is "We Will Survive," and it was thumping through the back of my head on the evening last week when I stood in my son's third-grade classroom and saw on the wall the assignment he had written titled "Five Most Important Things That Happened to Me." The earthquake was one of them, but so was receiving a stuffed otter from his grandmother for Easter. Most of the time, he sleeps through the night.