The iron stars and S shaped strips of metal bolted into the aged brick of Old Towns centuries-old buildings seem ornamental, but theyre actually called earthquake bolts.
Except when theyre called hurricane bolts.
It depends on whichever is more prevalent in your neck of the woods, said Al Cox, the citys historic preservation manager. Alexandria has experienced both natural disasters in recent days, making the terms interchangeable. Whatever you call them, the conspicuous symbols are actually washers at the end of an iron rod running through the heart of aging masonry, holding it together.
Once installed, the rods should prevent walls from bulging, which in turn keeps floors from dropping out on multiple-story buildings, Cox said.
If that wall spreads, then the floors would fall, he said. This keeps [the walls] from spreading apart. That could be from wind pressure from a hurricane, the sudden movement from an earthquake, or in Alexandria it could just be foundation settlement over time.
Local legend has it many of the bolts, found inside and outside many of the federal style buildings of Old Town, were installed after Virginias last big trembler, a 5.8-magnitude earthquake centered in Giles County in May 1897.
While Augusts 5.8-magnitude quake rattled the nerves of city residents, drew front-page coverage and caused damage in Alexandria and Washington, the 1897 event earned little mention in the Alexandria Gazette.
It struck about 2 p.m., May 31 and lasted about 50 seconds, causing chandeliers to sway and floors tremble perceptibly, according to the 19th-century newspaper accountr.
It was noticed at the Capitol, in the telephone exchange and several of the high buildings, the Gazettes Washington correspondent noted. In the Associated Press office in the Post building the vibrations were felt very distinctly.
The quake caused no damage in Alexandria and earned a one-paragraph follow-up story a day later. The tremors were felt in southern and middle-western states, according to the Gazette.
Here it was a slight tremor, which repeated itself after the lapse of some seconds. Both shocks were distinctly felt by people who were in the quietude of their homes or lying down, the newspaper reported.
While linking the prevalence of earthquake bolts to an actual seismic event is tempting, Cox says theres no way to know for sure whether the two are related.
The S shaped washers could have been installed as early as the first half of the 19th century, Cox said. The cast iron star washers were probably installed in that centurys latter half. Before then cast iron was harder to come across, he said.
While Alexandria has weathered earthquakes and hurricanes in 2011, the bolts were likely installed for a third reason: the citys soft, clay-like soil.
Given the quality of the soil in some specific areas where we have the marine clay and other soft soil, historically foundations werent terrible deep or had widespread footings, Cox said. I would think in some cases [the bolts were installed] shortly after the houses were built, in other cases maybe a hundred years later.
With the recent earthquake and hurricane still on many minds the tremors damaged chimneys, Gadsbys Tavern and City Hall, among other buildings Cox expects the board of architectural review to start fielding phone calls from residents anxious to install new earthquake bolts.
For city homes built around or after World War II, theres not much to be concerned about, he said, but Old Town homeowners may want to have an engineer poke around.