By Michael FleemanLOS ANGELES (Reuters) - The mayor of Los Angeles proposed on Monday that the city retrofit thousands of older buildings and bolster the water and communications systems to prepare for a possible major temblor along the San Andreas Fault.The proposals marked the first major earthquake-preparation initiative by the country's second largest city since the 1994 Northridge earthquake that killed 16 people and destroyed many structures similar to those now targeted for upgrading.'We know the 'Big One' is coming, it's a matter of when. If we're unprepared, the effects could be devastating,' Mayor Eric Garcetti told a news conference at City Hall. 'These things come with real costs, but we cannot afford not to pay them.'The recommendations are based on a one-year study headed by the mayor's science adviser, Lucy Jones of the U.S. Geological Survey, best known to Southern Californians as 'The Earthquake Lady' for her many appearances on television during temblors.Jones said the proposals were "by far" the most comprehensive step toward earthquake resiliency the city had ever taken. Garcetti estimated the measures would cost billions of dollars, to be shared by the public and private sectors.The measures, which require City Council approval, target pre-1978 apartment buildings with weak first floors, of the sort constructed over parking garages supported by narrow columns or poles. The proposal would require landlords to upgrade them within five years at an estimated cost of $5,000 a unit.Pre-1976 concrete buildings with columns and frame connectors that are brittle and can break during an earthquake would also have to be upgraded within 25 years at an estimated cost of $10 to $15 a square foot.The proposals also include upgrading the city's century-old pipes, developing an alternative water supply for firefighting with reclaimed water and seawater, and fortifying the dozens of aqueducts that cross the San Andreas Fault, including an old city water tunnel built of wood.The mayor also proposed fortifying the communications system by strengthening cellular phone towers, forging an agreement between cell and Internet providers to share service and bandwidth during an earthquake, and working with utilities to protect power lines that cross the fault.Money for the water and communications projects would come from a combination of public and private sources, much of it left to be determined, the mayor said.(Editing by Cynthia Johnston and Peter Cooney)Join the conversation about this story Click here to read full news..