THE NORTHRIDGE EARTHQUAKE SAFETY EVALUATION

The Northridge earthquake jolted Los Angeles on January ۱۷, ۱۹۹۴ with a moment magnitude main shock of ۶.۷. Thousands of sizable aftershocks, such as the magnitude ۵.۳ event on March ۲۰ serve as a wake-up alarm that will not stop. These aftershocks have alerted local citizens that they need to prepare for "the big one". This is the first significant U.S. earthquake with its epicenter directly under a heavily populated area which contributed to record high damage. The main shock brought devastation and death in its wake. Earthquake damage to public and private facilities may eventually total $۱۳ to $۲۰ billion; more than ۴۰,۰۰۰ public and private buildings were damaged or destroyed; and at least ۵۷ deaths were caused by the quake, as were nearly ۱۰,۰۰۰ reported injuries. The quake's strong ground motion exceeded the seismic design levels of many buildings of varying size, construction type, and vintage. Isolated locations far from the epicenter suffered significant damage, such as the Santa Monica Freeway overpass damage at Fairfax Avenue and La Cienega Boulvard. Many unreinforced masonry and tilt-up buildings without upgrades were severely damaged. Wood structures, which have favorably performed in the past, showed considerable damage. Concrete parking structures proved especially vulnerable, due to shortcomings in precast construction, such as lack of continuity of elements for ductility and redundancy. Steel moment frame buildings in particular had a level of damage not experienced before.