On the day Marriott Corp. opened its 1,500-room hotel in downtown San Francisco last fall, an earthquake shook the bay area. For Marriott, it was a bad omen.

The Bethesda-based company built the hotel with the intention of selling it, but one year later, the hotel is 39 stories of unrealized expectations. Marriott still operates the $300-million hotel, among the largest and most expensive ever built by the company, but has not closed a deal with a buyer.

The San Francisco property is merely one of many hotels and other pieces of real estate that Marriott is trying to sell. The growing backlog, coming amid a slump in the real estate and hotel businesses, is rapidly transforming Marriott from a 1980s success story into a shaken giant.

After a decade of dizzying growth -- Marriott's sales tripled from 1980 through 1985, then doubled again to $7.5 billion last year -- the hotel and food-services company all of a sudden is struggling.

The company's uncertain prospects have battered Marriott's stock and threaten to cripple its profits for several years. Layoffs, previously unthinkable at a company with a history of taking care of its own, have nibbled away at its work force -- with another round to come by the end of the year.

Corporate purchasing executives are even considering such cost-cutting measures as using cheaper varieties of soap in Marriott hotels and lesser grades of meat in company-managed cafeterias.

Despite these gathering clouds, Marriott executives said their company, second largest in the Washington area after Mobil Corp. of Fairfax, is far from imperiled.

"We're not panicked, but there is a real sense of urgency," said William Shaw, chief financial officer and second in command.

The concern surrounding the company has led to huge losses, at least on paper, for the Marriott family itself. Fourteen months ago, when the company's stock was selling at its peak price of $41.25 per share, the family's 29 percent stake was worth $1.1 billion.

At Friday's price of $9.87, the stake now is valued at $266.6 million. Such a sharp decline can be costly for the company too, since lenders use the stock price as one gauge of a company's credit worthiness and thus a means of determining its borrowing costs.

Shaw repeatedly stressed that the company's financial health was sound. The revenue generated by its hotels and other businesses continue to provide more than enough cash to cover expenses and interest payments on Marriott's $3.3 billion in long-term debt, Shaw said.

Shaw said that slightly more that half of this income stream comes from Marriott's contract-services division, a collection of low-profile, albeit stable, businesses that include janitorial services, hospital-cafeteria operations and airport restaurants.

Even if a recession cuts into the number of people checking into Marriott hotels, he said, these businesses will insulate the company in a downturn.

Chief executive J. Willard "Bill" Marriott Jr. declined to be interviewed for this article. Associates said Marriott has resumed full-time work at the company 11 months after undergoing open-heart surgery following two mild heart attacks.

In many ways, the company is stumbling because of its stunning growth. While best known for the 613 hotels and motels it manages worldwide, Marriott's main corporate activity for the past 10 years has been real estate development. Its basic strategy involves designing, financing and building hotels, which it then sells to investors.

By reinvesting the proceeds from the sales into new hotel construction, Marriott found that it could perpetuate its own growth spiral. Cash from selling the hotels provided some of the profit, but the real money came from the contracts Marriott signed with the investor groups that hired the company to manage the properties.

The strategy worked as long as there were investors willing to buy new hotels and enough travelers ready to fill them. But with air fares climbing because of rising oil prices, hotel occupancy rates nationwide are slipping: hotels filled 65.7 percent of their rooms in September, down two percentage points from September 1989, according to Smith Travel Research in Tennessee, which predicted the slump will continue through mid-1991.Further, with real estate prices falling in many parts of the country and lenders under pressure, Marriott is vulnerable to the same dangers that have devoured smaller developers and are wounding banks, thrifts and insurance companies.

Indeed, Marriott's pipeline of unsold properties is quickly filling up: At the end of September it had $1.3 billion worth of real estate in search of buyers; $1.1 billion under construction will be added within the next year. The company has ruled out any new development for at least the next year to 18 months.

Hotels and motels make up most of the property in the real estate portfolio. But Marriott also is trying to unload time-share resort condominiums, Bob's Big Boy coffee shops and apartments for senior citizens. Among the harder-to-move items for the past year has been an $8 million sheep and cattle ranch near Middleburg, Va., that was once part of a family retreat owned by Marriott's late founder, J. Willard Marriott.The slowdown is being felt by Marriott's work force. The company confirmed last week that merit-pay increases would be delayed next year for all salaried employees. The unhappy news came on top of a series of layoffs that have cut 450 people during the past six months. Although that is a small fraction of the 16,500 people Marriott employs in the Washington area, layoffs had been virtually unknown at the company until this year.

"It kind of caught all of us by surprise because Marriott has such a strong name in this area and around the world," said one employee, who requested anonymity. "That lulls you into a false sense of security. You feel insulated from the rest of the world."

The employee, who works in the hotel construction division, laments that Marriott's recent decision to slash its construction spending, "has put an ax over my head and the whole department."

"This company still has that family feeling to it, and that makes the whole situation extremely difficult to bear," the worker said. "When you're a family and all of a sudden you're seeing things broken up, it's very sad."

Cliff Ehrlich, Marriott's top personnel officer, said he expected additional layoff announcements by the end of the year. Ehrlich declined to be more specific, but the company indicated it would eliminate fewer than the 450 people it already has laid off.

The real estate market has increased the pressure on Marriott in other ways. Last month, the three major bond-rating agencies downgraded Marriott's creditworthiness, citing its real estate holdings and sluggishness in the tourism market as factors.

The actions by the agencies have made it somewhat harder and more costly for Marriott to find the money it needs to fund its operations. In the midst of the downgrade, Marriott was forced to reduce its reliance on short-term loans, called commercial paper, and begin drawing on backup credit lines supplied by its bankers.

The bank loans carry interest rates about 0.25 percent higher than the rates paid on commercial paper, but the additional cost is a small price to pay to avert what otherwise would have been a severe cash squeeze.

In the meantime, analysts are considering the worst-case scenario for Marriott's real estate. Assuming there are no sales, Joseph Doyle of Smith Barney Harris, Upham & Co. estimated company's profit would be reduced by $50 million next year, or 36 percent of what Marriott is projected to earn this year. The San Francisco Marriott alone will rack up $11 million to $19 million in interest and depreciation expenses next year if it isn't sold, he said.

"My expectation is that they are looking at an extended period of limited {ability to sell hotels} and pressure on their earnings," said John Rohs of Wertheim Schroder & Co. in New York.

Marriott's Shaw is more upbeat. "We aren't under any pressure to sell assets," he said. While recognizing that profits would be hurt by holding onto the real estate, Shaw said the cost of building the hotels will be partially offset by the hotels' revenues.

Shaw counsels patience: "When this period is behind us, there will be some tremendous opportunities because no one else is building hotels. There will always be people who want to invest in real estate and the pressure on lenders will be relaxed at some point. We've never seen greater long-term opportunity for our company.

"On the other hand," he said, "we would be the first to admit that we've never seen greater short-term challenges."