Los Angeles County, implementing a new earthquake ordinance, has notified owners of 74 old masonry buildings that they must buttress the structures by 1991 or demolish them.
About 80% of the buildings are shops, stores, restaurants, offices and apartment houses located in the Firestone area south of Huntington Park or along busy commercial strips in East Los Angeles. Three are small churches.
The buildings, all erected before 1934, are considered the most dangerous in the county's unincorporated areas because their brick and block walls are not melded to floors or roofs with steel and tend to collapse during severe earthquakes, county engineers said.
Owners of 210 other unreinforced masonry structures--also concentrated in the Firestone and East Los Angeles areas--will be required to make their buildings safer against earthquakes by 1994, they said.