California is renowned for its pristine beaches, wild mountains, hot individuals… and earthquakes. Second only to Alaska as the U.S. country that encounters the most earthquakes, California is particularly concerned with finding methods to protect its own citizens. As understanding of earthquakes has improved and technology has enhanced, California has come up with better ways of earning structures sound sufficient to withstand a quake.
1971 Sylmar Quake
On February 9, 1971 an earthquake struck the San Fernando Valley, just north of Los Angeles. It registered a 6.4 on the Richter scale, but had a seismic moment of 6.7, and did enormous damage to the area. 58 people were killed and 2,543 were suffered injuries. Two major hospitals were destroyed and four freeways and overpasses failed. The State of California decided after that earthquake to produce significant enhancements to its construction codes pertaining to earthquakes. In Los Angeles, the Sylmar Quake caused the passage of an ordinance that required retrofitting of more than 8,000 unreinforced masonry buildings with the best threat of collapse.
The effects of the developments to construction code could be seen in the 1987 Whittier Quake, 1991 Sierra Madre Quake, 1992 Landers Quake, and 1994 Northridge Quake. Los Angeles city officials state that more than 200,000 individuals were living in retrofitted brick buildings with an Northridge Quake hit. Not one death or injury was reported out of more than 37,000 units in 1,300 strengthened buildings. The structures that were built or strengthened under the new, stricter code experienced limited damage, while those constructions that had been retrofitted suffered greater damage.
Features Of Building Code
The revised building code requires special tests for any masonry that’s used to build new buildings. Brick walls need to meet specifications for confronting, bonding and distance between headers. Masonry must be analyzed utilizing an in-place shear test that displaces a single brick, then applies checks and weight for motion. Wall anchors are tested and must pass code demands, and embedded wall bolts are inspected periodically.
The Demand For Retrofitting
Recent earthquakes in California have supplied evidence of how effective the new construction codes are when it comes to construction and retrofitting. However, there are still many older buildings in California that have yet to be retrofitted, and it is up to the owners to achieve that. If you are not certain whether the building you work or reside in has been retrofitted, ask your landlord, then guides the Southern California Earthquake Center.