A report that was released recently revealed dozens of high-rises in San Francisco all share a features that be detrimental when the next major earthquake strikes. The buildings were all completed between 1964 and 1989 all have steel skeletons. They are connected with a welding technique that experts now known to fracture during an earthquake. Since San Francisco inspectors never checked for the same kinds of fissures after the magnitude 6.9 Loma Prieta, damage to the buildings’ frames could have gone undetected for decades. City officials are figuring out how to implement new requirements to ensure that buildings that might have sustained unseen damage from the Loma Prieta quake get the scrutiny they need.

For more info, please read the original article by SF Chronicle:
https://www.sfchronicle.com/science/article/68-SF-high-rises-crack-earthquake-which-ones-safe-13418917.php