Following a period of calm along California’s fault lines, earlier this month a 6.4 magnitude earthquake hit in an area outside Ridgecrest, California, quickly followed by a series of aftershocks and a 7.1 magnitude quake in the same area.
Now one of the big questions is, are buildings and infrastructure in the state up to par to withstand a larger quake in the future? Derin Ural, professor of civil engineering in the University of Miami College of Engineering, said it is hard to say.
“This latest quake was significant and the damage was very minor. If this earthquake were to have hit closer to Los Angeles the damage would be unknown, but I know the state of California has done a lot in terms of reinforcing critical facilities and its infrastructure,” she said.
Ural said building codes have evolved significantly throughout the last four decades. Since the San Fernando earthquake of 1971, engineers have been working to update codes and make them better.
“Damages of each significant earthquake have given a window of opportunity for change,” she said. “Engineers reevaluated and learned from what went wrong. They’ve made a lot of progress with these seismic design codes.”
In terms of this recent earthquake near Ridgecrest, she thinks it was a success story for structural engineering. When engineers arrived to the affected area, they expected to study severe destruction from the largest earthquake to hit southern California in nearly 20 years, but found barely anything.
“Records show that if this magnitude earthquake would have happened in many other seismically active countries, it is likely that there would have been significant damage and loss of life. To see that the structures withstood the shaking is affirmative for engineers and local governments in charge of code enforcement,” she added.
Ural said the reason why there was such minor damage was because most of the buildings in the area of impact were built after the 1970s. She said it is so important for everyone who lives in a megacity to know more about the infrastructure they are living in.
“The structures that are at risk are unreinforced masonry, and soft-story buildings which is a multi-story structure built with one floor that includes large unobstructed spaces without shear walls or columns,” she said.
Progress to these vulnerable homes has been made by cities including Los Angeles and San Francisco. Los Angeles recently passed an ordinance that requires the retrofit of pre-1978 wood-frame soft-story buildings and non-ductile concrete buildings. The goal of the ordinance is to reduce structural deficiencies and improve the performance of these buildings during earthquakes. Although Los Angeles has passed safety laws, several major cities have not. Cities including Long Beach and Pasadena have not mandated any specific retrofitting ordinances.
Ural said it is important for states susceptible to earthquakes to teach residents how to mitigate non-structural damage.
“During this earthquake most of the damage was caused by secondary hazards such as fires, as well as non-structural items falling over inside buildings. I think public education on non-structural mitigation measures, which includes how to prepare a person’s home and work environment is a necessity,” Ural said.
