On the afternoon of 17 October 1989, a 6.9-magnitude earthquake rocked the San Francisco Bay Area, killing 63 people and causing $13bn in damages as it toppled a chunk of the Bay Bridge, collapsed a section of freeway in Oakland, and crumbled thousands of buildings from San Francisco to Santa Cruz.

Thirty years later, California will launch an earthquake early warning app, the first to cover the whole state, developed by UC Berkeley and the California Office of Emergency Services. The decades since the Loma Prieta quake have been remarkably quiet – yet it’s not a matter of if, but when, the next large earthquake will rattle the Bay Area, and the consequences will undoubtedly be severe.

There are multiple faults to worry about in the Bay: the infamous San Andreas is a system, with branches that run up the San Francisco peninsula, along the East Bay foothills through Oakland and Berkeley and further inland through Dublin and Walnut Creek.

Just this week, a 4.5-magnitude quake with an epicenter in the Pleasant Hill area shook the region.

An antenna to send data stands on a rise above an earthquake monitoring well, right, powered by a solar electric panel, lower left, as scientists from the US Geological Survey set up an earthquake monitoring station on the San Andreas fault. Photograph: Reed Saxon/AP

In the case of a major earthquake, experts are particularly worried that “ground failures” will cause widespread structural damage in many parts of the region built on landfill and sand. The California Geological Survey’s most recent map of earthquake hazards shows huge swaths of the inner Bay Area are in “liquefaction zones”, meaning that during a major earthquake, the ground could be shaken so violently that it would very temporarily soften into jelly.

“People love to ask the question: is X place prepared for X disaster? Is California prepared for the next earthquake? The answer to that question, 99.99% of the time, is no,” said Dr Samantha Montano, assistant professor of emergency management and disaster science at the University of Nebraska Omaha. “The way we think about preparedness is really kind of weird. When we talk about it day to day: do you have an emergency kit, yes or no? Just because you have that doesn’t mean you’re prepared for an earthquake – there’s a lot more going into that.”

For any community facing a potential wide-scale disaster, the preparation is twofold: mitigating risk and preparing for the inevitable management of the emergency.

While newer, stricter building codes put in place after Loma Prieta have required more quake-resilient construction, thousands of buildings in the Bay Area were built using old, shaky standards. Oakland passed an ordinance in 2019 requiring owners of vulnerable apartments to retrofit their structures. In San Francisco, where retrofits were due to be completed in 2018, about three-quarters of susceptible units have been quake-prepped.

Politicians in Berkeley cited earthquake risk as one motivator for moving to ban natural gas hook-ups in new buildings earlier this year.

Officials and others evacuate a man, Erick Carlson, from the Cypress section of Highway 17, now called Interstate 880, in Oakland, California, following the Loma Prieta earthquake. Photograph: Michael Macor/The Oakland Tribune/AP

“We have basically allowed ourselves to pump a toxic flammable greenhouse gas producing an expensive liquid into our homes across earthquake fault lines,” the Berkeley city councilmember Kate Harrison said at the time. “It will seem crazy in 100 years. We can see that this is a dangerous situation.”

The East Bay had perhaps a little taste of that danger earlier this week: following the mid-sized East Bay quake, two of the area’s five refineries shut down due to the “upset” and their built-up gasses flared.

Later, on Tuesday, a NuStar energy fuel storage facility suffered an explosion and large fire, leading many to speculate the earthquake had triggered the accident. A spokesperson could not confirm the cause of the explosion, which some in the area said felt like yet another earthquake.

“We want local governments to really be taking the lead and making sure not only that there’s a plan for the city’s government but also that they’re integrating the plans with communities and businesses – particularly businesses like refineries, where there could be an added hazards,” said Montano.

#BREAKING : WOW! You can see the tank's top being blown off during this giant explosion at a NuStar refinery in Contra Costa County. According to fire officials, 3 large tanks of ethanol are burning. @kron4news https://t.co/b1zIju9159 pic.twitter.com/IYy6NNcRhP — Amy Larson (@AmyLarson25) October 15, 2019

Environmental justice activists in the East Bay city of Richmond cite this kind of risk in the bigger quakes to come.

“When the Hayward fault shifts, and we have that earthquake, the reality is, large portions of the Chevron refinery are built on landfill,” said Andrés Soto, an organizer with Communities for a Better Environment in Richmond. “And despite the best assurances from Chevron about how they’ve secured their refinery in the event of an earthquake, nature seems to have a way of conquering man-made structures.”

A transition away from the fossil fuels that in turn contribute to several other impending California environmental disasters could help make the Bay Area more resilient when the big one inevitably hits.