A groundbreaking report was released Thursday looking at the seismic safety of tall buildings in San Francisco.
The report reveals some buildings that withstood the Loma Prieta earthquake may have sustained damage not previously known about.
After the 1989 earthquake, engineers gathered new data about how certain buildings fare when the earth shakes. Five years later, another quake: a different vulnerability emerged.
"The type of fractures that occurred in the 1994 Northridge earthquake occured in a type of welded steel moment frame that was popular for buildings of various heights," said Greg Deirlein, an engineer professor at Stanford University.
Deirlein is also a co-author of the report "Tall Buildings Safety Strategy."
NBC Bay Area's Christie Smith has more in the video report above.