Great
Earthquakes In Diverse Places
Earthquake damage at the US National Cathedral will take
years to repair
Nikki Kahn/THE WASHINGTON POST - Chief stonemason Joe Alonso
examines the damage at the Washington National Cathedral a day the
earthquake.
By — Margaret Webb Pressler, Updated: Tuesday, September 13, 2:54
PM
When a 5.8-magnitude earthquake struck the Washington area last
month, what seemed like one of the city’s strongest buildings
turned out to have some of the worst damage: the National
Cathedral.
Several slender carved pinnacles on top of the cathedral, which
are 45 feet tall, were cracked or damaged. “It’s hard to see, but
a lot of them just rotated,” said Joe Alonso, who manages the
cathedral’s stonework.
One four-ton section of a pinnacle fell onto the roof of the
cathedral’s 301-foot-tall central tower, as did several finials,
which are pieces at the very top of a pinnacle. All the pinnacles
on the main tower will have to be removed and fixed, Alonso said.
Why the cathedral?
Throughout the city, the damage caused by the earthquake was
fairly mild. But the cathedral is different from your house in two
important ways: It is made of stone, and it is very, very tall.
Both of those factors exaggerated the impact of the shaking earth.
The Washington Monument, another tall stone structure, was also
damaged by the quake.
“The cathedral is a big, heavy building, and it’s stiff — it’s not
made to be flexible,” said Bill Leith, a seismologist (earthquake
scientist) with the U.S. Geological Survey. “Modern skyscrapers
and steel buildings are made to be flexible . . . and not be
damaged” by most quakes. Work on the cathedral began in 1907 and
was completed in 1990.
When the earthquake hit, waves of energy from the shaking ground
passed up through the cathedral, but the walls didn’t respond by
bending or swaying, so pieces at the top broke off when the energy
reached them.
The worst damage was at the cathedral’s tallest point. It’s a
matter of physics: Motion increases the higher you go. You’ve seen
this at work if you’ve ever built a Lego tower: When you move the
base even slightly, the top sways like crazy.
This is also what happened at the Washington Monument, which also
remains closed after several stones near the top were slightly
dislodged or cracked. “At this point we really don’t know when it
will reopen,” said Carol Johnson of the National Park Service.
“But I can tell you it will reopen, and it is not leaning.”
Fixing it
The good news is that “the main structure of the cathedral is
sound,” Alonso said. But the cathedral can’t reopen until all the
damage is inspected and loose stones are secured. That could take
weeks or months.
What Alonso does know is that it will take years, and millions of
dollars, to completely restore the cathedral. One carved angel
that broke off the tower, for example, would take about 50 hours
of carving to replace.
“Every one of those pieces up there is hand-carved,” Alonso said.
“And that’s just a lot of hand work.”