A dark dropcloth known as the "black shroud" envelops City Hall these days to protect pedestrians from falling tiles. Yellow-tagged from the massive Northridge earthquake that roared through the city on Jan. 17, 1994, the building is still so damaged that 18 stories above the fourth floor are vacant.

Instead of a symbol of law and order, City Hall now seems more like a testimony to Los Angeles's seismic vulnerability. With reinforcement work stalled because costs have ballooned from $112 million to $242 million, it is a prominent reminder of the obstacles the entire city faces as it tries to recover from the last calamitous temblor and fortify itself against the next.

A recent study by the city on earthquake susceptibility and damage found that 80,000 buildings, including 50,000 single-family houses, should be retrofitted or strengthened against seismic jolts through various measures such as adding steel rods, pouring more concrete and bolting structures to their foundations. Even though that amounts to only about 8 percent of the city's buildings, the cost would be hundreds of millions of dollars at best, city officials said. And even if the money could be found, the retrofitting would take a decade to complete.

The City Council will vote in coming months on whether to adopt the ambitious recommendations, and safety experts are hoping the fresh memories of the 1994 earthquake, in which 57 people were killed and 9,000 injured, will force some changes. Some see the decision as a choice between saving money or saving lives.

"To let these buildings stand and wait is just courting disaster," said Los Angeles Councilman Hal Bernson, a former California Seismic Safety Commission official and strong proponent of mandatory retrofitting. "It's not going to be easy; it's going to be expensive. But there's an absolute necessity to do it."

Not everyone is convinced. Doubters cite the high cost to government and the private sector and the uncertainty about whether retrofitting would make any difference, particularly for taller, more complex buildings.

"We don't really know how to make them technologically sound," said Richard Andrews, director of the California Office of Emergency Services. "There still is a significant debate within the engineering community on how this should be done and can be done at a reasonable cost."

But with California lurching from one quake to another, a sense of urgency about vulnerable buildings has increased. During the Northridge earthquake, which occurred at 4 a.m. on the Martin Luther King Jr. holiday, 11,000 buildings were seriously cracked or wrenched off their foundations, freeway bridges plunged to the ground and several buildings collapsed into piles of rubbish.

The death and injury toll was considered low by experts, who say the casualties easily could have been 20 times higher had the earthquake occurred during business hours. The city estimates that economic damage from the quake was more than $25 billion, making it the most expensive in the last 50 years here. But with a seismic motion of 6.7 on the Richter scale and only nine seconds of violent shaking, the quake was described by scientists as only a "moderate" shock.

Indeed, many scientists believe it is just a matter of time before a real seismic whopper slams Southern California, one vastly more deadly, registering 7.0 or more on the Richter scale. Whether the quake strikes one of the hundreds of faults that underlie the Los Angeles basin and whether it rolls away from downtown like the Northridge temblor or, worse, into the city -- as one did in Kobe, Japan, a year ago -- no one can predict.

Eighty percent of California residents live very close to an active earthquake fault, according to Fred Turner, of the California Seismic Safety Commission. Even so, voters have not been very willing to fund proposals to make buildings safer; several large state bond issues to finance retrofitting have been rejected.

The state has gone ahead with retrofitting and more stringent building codes for public schools, hospitals and freeways. State officials emphasize that California has some of the strictest earthquake safety guidelines in the world and that some headway has been made in recent years to strengthen basic infrastructure.

But what has been done covers only a fraction of the vulnerable buildings.

Officials said that more than 1,000 bridges still need to be retrofitted. The vast majority of hospitals are not up to standard. Like City Hall, there are legions of public buildings that were built according to outdated earthquake safety codes.

Since a major earthquake in 1933, some 10,000 old brick buildings found to be highly susceptible to collapse still have not been retrofitted with the steel rods engineers say will make them sturdier when the ground shakes.

In addition, reinforcement still is not required of a certain type of concrete building and parking structure that pancaked in a 1971 earthquake. Other concrete buildings have ceiling and wall joints that are too weak; in the 1994 earthquake, some separated, often with devastating results. Retrofitting these structures is among the recommendations the Los Angeles City Council will be addressing.

But a newly discovered hazard that "shocked" engineers and is not part of the panel's retrofitting objectives concerns the tallest buildings in Los Angeles. High-rises made with steel frames, found in abundance downtown, were long thought to be the most earthquake-safe constructions because of steel's flexibility and strength. The 1994 quake proved otherwise, when inspectors found cracks in the joints of beams that had been welded together.

The city passed a law requiring all steel buildings to be inspected and repaired as necessary, but this is much less drastic -- and sturdy -- than retrofitting.

Engineers and others are hoping this frightening list of earthquake vulnerabilities will help build support for a more dramatic response to the problems. But the price remains daunting.

"It does very little good to mandate something if it wrecks your economy," said Zan Turner, an inspector for the Department of Building Inspection in San Francisco, who was part of the panel that determined how many structures Los Angeles needs to strengthen.

With California just beginning to rebound from a long economic slump, few here are eager to shoulder new financial burdens.

Building owners, who have watched real estate values plummet in recent years, have said they cannot afford to pay the high costs of retrofitting. Many homeowners, who purchased houses when prices were much higher, have mortgaged their properties beyond their current value.

"People are already losing their buildings left and right because of foreclosures. They've already been beaten up. To hit them with this -- there are people who will lose their buildings," said Dan Faller, president of the Apartment Owners Association of Southern California. "It may be hard and cruel, but how can apartment owners be asked to save all these lives?"

Some city officials are hoping the state will step in and ease retrofitting costs by offering owners tax breaks or other financial incentives to fortify their properties. They also are trying to work with insurance companies and banks to lessen insurance or mortgage costs for seismically improved structures.

And there is the hope that, despite budget problems in Washington, D.C., the federal government, which pledged a potential $12 billion package to help California recover from the 1994 earthquake, might come to the rescue.

"People often ask us, Can't we make buildings much stronger?' Yes, we can," said David Keim of the Los Angeles Department of Building and Safety. "The bottom line is it all costs money."

Until officials find the resources to build a stronger city, they are just hoping the ground doesn't tremble. CAPTION: Work crews begin demolishing part of the Santa Monica Freeway a day after the Jan. 17, 1994, earthquake in California, which killed 57 people.