The small earthquake that jolted downtown Los Angeles last week added a geological exclamation mark of sorts to the escalating debate over the fate of St. Vibiana's Cathedral, even though the temblor caused no new damage to the historic seat of the nation's largest Roman Catholic archdiocese. There's no question that something must be done about the sad and unstable state into which this genteel building has fallen.

The 1994 Northridge quake racked the 120-year-old cathedral. Its bell tower was damaged, and walls were cracked throughout the structure; the building later had to be closed to worshipers because of fear that it might collapse. But St. Vibiana's remains an integral part of downtown, historically, politically and sentimentally. Should the woes that have befallen the old cathedral mean that a new archdiocesan seat must be built somewhere else? We think not.

The archdiocese says it is now so frustrated with the slow pace of its effort to build a new cathedral at the downtown site, at 2nd and Main streets, that it is considering moving the archdiocesan headquarters, perhaps to the San Fernando Valley. That frustration is stoked by a variety of causes: a clash with conservationists over restoring the old cathedral; the high costs of such a restoration; the likelihood of grueling encounters with city bureaucrats over the permitting and construction of a new facility at the present site, and the rising price of adjacent property that the archdiocese has indicated it would seek to buy to accommodate an expanded cathedral complex.

Building a new cathedral on one of the large parcels the church owns elsewhere in the city would certainly reduce costs--now estimated at up to $60 million--by eliminating the need to acquire downtown property at opportunistically rising prices. Moving outside the city limits, beyond the reach of Los Angeles' building inspectors, might speed the permitting process. Moving might also moot the unpleasant fight between the archdiocese and the Los Angeles Conservancy over the cathedral building, designated a city historic-cultural monument. The conservancy wants the archdiocese to retrofit and restore the California-Spanish-style building and incorporate it into a new facility; citing exorbitant costs for retrofitting and restoration, Cardinal Roger M. Mahony says he wants the crumbling structure razed and something new built in its place.