The speed with which Bank of New England Corp. deteriorated in the final months of the year has startled analysts and raised new questions about the survival of several other banks, especially in the Northeast, where real estate problems are severe.

Most of the banks that are seen to be in most immediate jeopardy, however, are smaller institutions with assets in the $1 billion to $2 billion range. Banking experts also noted that federal regulators frequently have allowed money-losing or insolvent banks to continue operating unless panicky depositors create a run trying to get their funds.

Bank of New England, with $23 billion in total assets, had been struggling for survival but on Friday it reported a $450 million loss for the last three months of the year, much larger than most analysts had expected. The mammoth loss, coupled with the failure of a state-insured credit union system in neighboring Rhode Island, prompted a run on its three banks, leaving federal regulators no choice but to step in.

"The magnitude of the loss {Bank of New England} reported really surprised me," said James Moynihan of Advest Group Inc. in Boston. " ... That suggests to me that anybody else up here in the real estate lending business probably is going to come in with more depressing fourth-quarter results."

The big holding company had been battered by the collapse of real estate prices in New England as well as an overall slowing of the economy. Some of those conditions, while not as extreme, are beginning to be felt in most of the rest of the country, forcing banks from here to California to report losses and increase reserves.

The key question, several analysts said, is whether the economy will begin improving in time. As the slump goes on, more and more loans that are now paying -- "performing," in bank parlance -- will become nonperforming, forcing banks to place more money into reserves and cutting earnings and capital, or available cash.

"It's a race between capital and nonperformers -- which is going to run out first," said Don J. Kauth of First Albany Corp. in Albany, N.Y. He said that while none of the other big New England banks is as badly off as Bank of New England, "the question is where we are going to be at the end of March, at the end of June... . It's clear the economy hasn't bottomed yet."

If Bank of New England's last quarter means that things have turned down even more, the scenario could change, he said.

Kauth said time has already run out on a number of second-tier banks in the Northeast, and others may not have long to go. For example, the One Bancorp, a holding company with $2 billion in assets and banks in Maine, Connecticut and Massachusetts, and New Hampshire Savings, a New Hampshire holding company with $1.4 billion in assets, are insolvent, he said, but have not been taken over by regulators.

Arnold Danielson of Danielson & Associates Inc., a bank consulting firm in Rockville, noted that regulators have not been hurrying to take over troubled institutions, and that suggests that, absent a crisis such as a run, many banks will get as much time as possible to work out their problems.

"The Bank of New England is so much worse off than anybody else and it took {regulators} so long to move on it that it would take anybody else another three quarters" to sink to a point at which regulators would move, he said.

Like New England institutions, many Washington area banks plunged heavily into real estate lending in the 1980s and are now suffering from a downturn in the market. MNC Financial Inc., Riggs National Bank of Washington and Signet Banking Corp. of Richmond are among the local institutions that analysts are watching with concern.

"MNC is not remotely having the same problem" as Bank of New England, Danielson said. The Baltimore company has $1 billion in capital while the New England company was allowed to run all the way down to zero, he said. By that measure, MNC could repeat the $200 million quarterly loss it reported recently, "and go five more quarters," he said.

A recent report to the House financial institutions subcommittee, which said the U.S. banking industry is in "serious trouble," listed 11 of the nation's 25 largest banks as operating at a moderate to high risk of failure.

"There's a large pool of large troubled banks out there," said one expert familiar with the report.

Most analysts said yesterday, though, that they expect almost all large institutions -- the big regional and giant "money-center" banks -- to survive.

Robert E. Litan of the Brookings Institution, who is one of the authors of the House subcommittee report, said his personal view is that the recession will be mild to moderate, and if that is the case, the federal deposit insurance system, with the $25 billion infusion it has asked for, should be able to handle any failures. However, if the recession becomes severe, far more rescue funds will be needed, he said.