So city officials required brick structures such as the landmark Alexandria Square building to get seismic retrofitting — bolting brick walls to ceilings and floors to make them stronger. The work was completed years ago on the 104-year-old property.

But when a 6.0 earthquake struck Sunday morning, the walls on the top floors crumbled, showering brick and mortar onto the sidewalk and outdoor café.

The destruction highlights one of the greatest fears of seismic engineers — that the retrofitting of unreinforced masonry buildings still leaves weak joints between bricks. Whole chunks can fall, sending bricks crashing down.
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When the quake struck at 3:20 a.m. Sunday, part of the third-story cupola collapsed onto the sidewalk below. A restaurant, Carpe Diem Wine Bar, has outdoor seating under broad awnings during the warm summer months. If the earthquake had struck at any other time, DeSimoni said, “we could have lost lots of people.”

“You can’t replace people, but you can put new brick on a building,” DeSimoni said. “We’re pretty fortunate that it happened when it did.”