More than $22 billion in infrastructure upgrades have built a metropolitan area that is far safer and far more resilient than before. It's a testament to the power of long-term planning, borne of the ashes of the tragedy -- 25 years ago Friday.

An extensive Bay Area News Group survey of our infrastructure offers much reassurance: Major water pipes are now designed to bend, not break. Bridges and overpasses can better support us. Gas and power lines are safer near fault lines. Hospitals are sturdier.

But our readiness to recover from the Big One gets far from a perfect score -- more like a C-plus, say experts who study quake preparation around the globe.

"A lot has been done," said Stanford civil engineer Anne Kiremidjian. "But to get a B, there's a lot more to be done.

"Our entire region is a very complicated system, and it all has to function together."

Decades of improvements buoy hope that while the Bay Area's $535 billion a year economic engine might sputter, it would eventually recover.

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