National Geographic : 1995 Apr
Wounded welds Safer than unreinforced concrete or brick in a quake, steel has been the material of choice for California builders. But some construction projects are on hold since Northridge, as en gineers scramble to fig ure out why steel welds cracked so frequently. The cracks appeared around welded con nections between steel columns and beams. Cracks (above) from a single quake the size of Northridge probably won't cause a building's collapse. A larger quake or cumulative damage from several quakes poses greater danger.