In the 20 years since the Northridge earthquake, the state's freeway bridges have been strengthened. A new generation of hospitals, schools and university buildings designed to better withstand a massive quake has risen.
But for all those strides, changes in society and technology have left California vulnerable in other ways.
The 1994 Northridge disaster occurred in an era before Wi-Fi computer access and at a time when cellphones were still something of a rarity. Seismic safety experts say that if a huge quake strikes the state now, both services would be interrupted — possibly for days.
The proliferation of personal technology offers some huge opportunities on the quake safety front, most notably a fledgling early warning system that one day could send alerts of a coming quake to phones, computers and tablets up to a minute before the shaking begins.
But it's what happens to those networks after the shaking that is generating increased attention from earthquake researchers and public safety officials.
When Los Angeles Mayor Eric Garcetti announced an extensive new earthquake safety effort Tuesday, he said one focus would be strengthening the telecommunication network.
"We created a society that requires the Internet to function," said U.S. Geological Survey seismologist Lucy Jones, who is heading L.A.'s new effort. "The Internet is adding this whole new level of ... complexity to our society."
Like water and gas lines, most Southern California Internet lines run across the San Andreas Fault, and officials fear the Big One could cut off service.
In the case of a huge earthquake, fiber optic telecommunication lines could be severed by the violent dislocation of the fault. Cellphone towers in areas that experience heavy shaking could collapse or be damaged, experts say.
Even if the towers are not damaged, a surge in phone usage after a major quake is sure to bring interruptions.
The relatively modest magnitude 5.5 Chino Hills quake in 2008 caused major problems with cellphone and land-line communications. Some cellphone companies reported up to an 800% increase in calls, far more than they had expected in a true disaster. Even phones in some police agencies near the epicenter were knocked off line.
The same thing happened after the 2011 Washington, D.C.-area quake. Several companies said that many customers struggled to make phone calls but could still send and receive text messages.
While police officers and other first responders have personal cellphones, they also use radio equipment that is much less likely to be compromised during a big quake.
Sgt. Daniel Gomez, who works in the Tactical Technology Section of the Los Angeles Police Department, said the computers in police cruisers use cellular technology but have data connections similar to text messaging that are more reliable than phone service.
The LAPD and other agencies, he added, also have backup communications plans so that even if a big quake takes out radio towers they "at no point would be totally out of commission."
Adam Rose, a USC professor and coordinator for economics for the Center for Risk and Economic Analysis of Terrorism Events, said many big companies have taken steps to protect themselves, like moving servers to locations less likely to be damaged by earthquakes.
"We're more vulnerable but we also have more coping mechanisms," Rose said.
Seismic experts say it's important to put the communications risk in context. They said damage to unstable buildings — which would bring loss of life — and the possible cutoff of the water supply are much more serious concerns.
But they argue the seismic risks to telecommunications need more study because so many basic functions are now controlled by computers.
"It used to be that grocery stores in Southern California had big warehouses in the Inland Empire where food was stockpiled," Jones told quake experts in a December speech in San Francisco. She said the development of the Internet helped create a more efficiency-minded "just-in-time economy" where far less food is stored on the L.A. side of the San Andreas fault.
Though the 6.7 Northridge earthquake killed about 60 people and caused billions of dollars in damage, experts warn that the region is overdue for a much larger temblor. A 7.8 or larger earthquake along the southern end of the San Andreas fault that has long been predicted would be exponentially more powerful and destructive over a much larger area.
If such a quake significantly affects telecommunications, Southern California is going to have to adjust to getting information more slowly than it does now, said Karen North, a social media professor at USC's Annenberg School.
"The first thing that's going to happen is that if a big quake happens, pretty much everybody is going to go to their digital devices to find out what's happening and to communicate with other people about it," she said.