Another powerful surge in interest came in 1985, when Robert Ballard and colleagues found the ship, bow and stern split apart, on the sea floor more than 12,000 feet below the surface. That incited an ongoing controversy over salvaging operations, with Ballard, for one, arguing that the wreck should be left alone.

The Titanic then reached a new level of cultural resonance with the Cameron movie, a love story and feminist parable in which heartthrob Jack Dawson (Leonardo DiCaprio) liberates Rose De­Witt Bukater (Kate Winslet) from a suffocating future in the patriarchal aristocracy.

A famous headline in the Onion’s 1999 book reviewing the 20th century — “ World’s Largest Metaphor Runs into Iceberg” — captured in a phrase the way the Titanic has ceased to be merely a maritime accident. It has replicated itself to the point that the real event seems increasingly swamped by the accounts of the event, and accounts of the accounts of the event.

Ed and Karen Kamuda point out that there are people who have gone to the graveyard in Halifax where Titanic victims are buried and have taken rubbings of the grave of a crewman named Dawson. That’s because it’s the name of the fictitious DiCaprio character.

The Titanic offers lessons not only in maritime safety and crisis management but in sustainable mythologizing. Events can defy the normal historical fading if they can speak to succeeding generations and become part of a common vocabulary. The Internet helps: Buffs can congregate more easily than in the old days.

Commercial interests have their say. Disasters are marketable. The Titanic lends itself to visual media. No one’s going to make a movie about the Treaty of Ghent (it ended the War of 1812, the bicentennial of which doesn’t seem to have inspired a tremendous upwelling of media interest).

At some point, the historical event inspires a self-sustaining body of literature, nurtured by amateur historians. There’s always another angle to explore. The Kennedy assassination is like this, as is, on a grander scale, the Civil War. New books about Lincoln have become as ubiquitous as ground squirrels. Next year is the 150th anniversary of the battle of Gettysburg, another mythic event that will surely be commemorated lavishly.

These topics are bottomless. If you get so deep you hit mud, you need to find out what’s below the mudline.

“I see all the stuff coming out today, I don’t have time to read all of it,” said Ed Kamuda.

Even a buff — even the original Titanic enthusiast — has his limits.