In the 20 years since the Loma Prieta earthquake, which crumbled
buildings near the coast and collapsed a section of the Bay Bridge
in San Francisco, state and local officials and scientists have
focused their efforts on improving the understanding of such
shakers and the damage they can cause.
In the 20 years since the Loma Prieta earthquake, which crumbled buildings near the coast and collapsed a section of the Bay Bridge in San Francisco, state and local officials and scientists have focused their efforts on improving the understanding of such shakers and the damage they can cause.
And while billions of dollars have been spent upgrading bridges and retrofitting sensitive structures, experts say we may never be fully be prepared for the next major quake, which will likely be more destructive than the 1989 event.
“There is no such thing as an earthquake-proof building,” said Tom Whisler, a building official in the Santa Clara County Office of Planning and Development. “There are levels of earthquake resistance. What’s happened over the last 20 years is an increased ability to resist an earthquake.”
Counties and cities in California have responded by keeping up with stricter state codes. Morgan Hill Planning Manager Jim Rowe said the city’s office of development services has adopted the more stringent state codes.
Santa Clara County officials have worked with people from the state to develop and write the new codes and legislation intended to strengthen buildings.
Specifically, one of the notable restrictions on local building since Oct. 17, 1989, is the elimination of stucco and interior drywall as building materials. These materials are likely to develop at least small cracks during an earthquake, and one crack can compromise the entire structure, Whisler said.
“You’re seeing more and more plywood required on buildings to better resist shaking,” he said.
And just this summer, the county adopted a resolution accepting a “residential seismic strengthening plan,” which is used by cities and counties throughout the Bay Area and ensures that local buildings are sufficiently earthquake-safe.
Although he was not in Santa Clara County in 1989, Whisler said substantial repairs were required on structures in unincorporated areas, and all the repairs were done at higher standards.
State-required seismic retrofitting is ongoing. Supervisor Don Gage said the county has been in the process of completing such improvements at Santa Clara Valley Medical Center.
“After an earthquake, patients have to be safe in the building, but also everything has to be working in the hospital,” Gage said. The county has secured a voter-approved bond to finance part of the hospital project. But they need at least $600 million more to complete $1 billion-plus in overall improvements, a difficult sum to acquire as the county suffers shrinking revenues and growing deficits.
Gage’s home in Gilroy lost “three or four tiles” on the roof. A Gilroy city councilman and IBM employee at the time, he said he had just arrived home from work, with his wife, when the earthquake struck. The only significant damage on his property was in his swimming pool, where he watched the water splash about 15 feet in the air, “like a volcano.”
A heightened understanding of the science of earthquakes since Loma Prieta has led to improved knowledge of how to build stronger structures, and finer details in local emergency response plans, according to U.S. Geological Survey and Caltrans officials.
Geologists at a press conference in Oakland Wednesday presented earthquake maps that can be produced within minutes following even the smallest rattler. Such simulations can identify what areas in the quake’s path were shaken hardest, and even suppose what kind of damage was suffered in different areas. That allows state, county and city officials to quickly determine where to send emergency service people.
In 1989, an earthquake map of Loma Prieta would have taken a week to produce.
“In the 20 years since Loma Prieta, the Bay Area has changed,” said David Schwartz, a geologist from USGS. “We’ve learned a lot about science, we have a better understanding of the regional fault system, how the ground shakes, and the probability that it will shake again.”
Still, the next major quake in the Bay Area will likely be bigger and stronger than Loma Prieta, and the extent of damage it could cause is unknown.
“We are a target in the Bay Area,” Schwartz said.
