Earthquake awareness focuses San Francisco on building safety and network resilience

Earthquake Awareness Week begins by thinking the unthinkable. Will there be a gas leak? Will these walls collapse? The city of San Francisco is taking steps to catalogue some of its concrete buildings, while PG&E is previewing its real-time monitoring measures in preparation for “the big one.” 

On Tuesday, Mayor London Breed announced an executive directive to kick start the city’s Concrete Building Safety Program. It follows the release of recommendations generated by the program’s year-long engagement with stakeholders. Recommendations addressed financing, temporary tenant relocation, ways to streamline the building process, and ways to communicate with building owners and tenants.  

Both actions fall in line with San Francisco’s 30-year plan for improving seismic safety. Building on previous improvements, the mayor’s Tuesday directive said, by October 16, the city must draft legislation that mandates a screening checklist for certain concrete buildings, and the San Francisco Department of Building Inspection must develop and publish retrofit criteria into the city’s building code.  

The mayor’s directive addressed two types of concrete architecture — non-ductile and tilt-ups. 

“Non-ductile concrete buildings were constructed with a limited amount of reinforcing steel, which makes them less able to flex in an earthquake,” said Laurel Mathews, a senior earthquake resilience analyst with the San Francisco city administrator’s office.  

“The concern there is that these buildings were constructed without enough steel reinforcement, so they’re too fragile for earthquake country,” Mathews said. 

The second type of building that will be screened is called concrete tilt-up. That is the kind of big-box architecture we see with warehouse retail companies, like Home Depot or Best Buy. The connection between the walls and the roof is too weak and needs to be strengthened, said Mathews. Most of the concrete buildings the city is concerned about are older ones constructed through the 1990s.  

“Many of the newer buildings are fine,” Mathews said. “Because they use more steel reinforcement, and they are more flexible and more able to bend when they are pushed sideways by an earthquake.” 

“Right now, our focus is to just identify which of the buildings in our city are actually concrete and to publish a retrofit standard so that building owners know if they decide to retrofit, what standard would be acceptable to the city,” said Mathews. “In fact, some of these concrete buildings most likely will be safe, but at the end of the screening phase and building information checklist, we’ll know, is this a concrete building or is it not.” 

Inside PG&E’s earthquake safety measures

Since the earthquake of 1868, the population of San Francisco Bay Area has increased by over 25 times, according to the U.S. Geological Survey. It is now a region of 7.2 million people, all at risk from expected earthquakes on one or more of the Bay Area faults. USGS said San Francisco has a 72 percent chance of experiencing an earthquake with a magnitude of 6.7 or greater by 2043. For comparison, the 1989 Loma Prieta Earthquake, in which 63 people died and over 12,000 people were displaced, was a 6.9 magnitude quake. 

Region-wide the impact of an earthquake affects the power and gas grid. PG&E opened its doors Tuesday to show the public its safeguards and explain how they maintain a system-wide watch.   

“PG&E has installed excess flow valves, buried deep in the street, that automatically shut off if too much gas is flowing, such as in a major leak,” said company spokesperson Denny Boyles. “This protects customers from a large gas leak caused by a building collapse.” 

PG&E also owns the transmission poles. Major lines contain not only electric transmission wires, but also communication lines that send operational data back to the company. Closer to home, smart meters tell PG&E that your house has lost power. At their base in San Ramon, they operate a room where they can watch their entire 70,000 square-mile gas and power service area, called the Hazard Awareness & Warning Center.  During major emergencies they embed with the state Office of Emergency Services to share information through Unified Command. 

“We provide close to real-time intelligence and situational awareness for any type of threat to the grid and to our employees and ultimately our customers,” said HAWC Supervisor Scott Cunningham. 

A wall of monitors features feeds that show current conditions from over 1,500 weather stations they have installed throughout the service area. Additional feeds come from CalTrans, CalFire, California Highway Patrol and various Twitter feeds.   

“Our big thing is, if it was a fire,” said Cunningham. “Was it the fire that caused the outage or did we cause the fire, right?”  

Note to readers: This story has been updated to correct a misquotation about non-ductile concrete buildings.