Loma Prieta earthquake 34 years ago could have been far more devastating in the Bay Area
SAN FRANCISCO -- Over three decades after the powerful Loma Prieta earthquake struck, some experts maintain that the strongest quake to hit the Bay Area since 1906 could have been much more destructive.
Legendary geologist and onetime head of USGS Menlo Park Allen Lindh suspected something was on the way. He leaned back in his chair in early October of 1989, and said, "Those Lake Elsman earthquakes. I know there's just something up with those."
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The two moderate shocks near Lake Elsman -- a magnitude 5.3 quake in June of 1988 and a magnitude 5.4 temblor in August, 1989 -- caused Dr. Lindh to stroke his robust then red beard and raise an eyebrow. The earthquakes struck a part of the southern Santa Cruz mountains segment of the San Andreas fault that was give a 30% probability of a M7+ earthquake sometime in the 30 years stretching beyond 1988.
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It only took sixteen months for the Loma Prieta earthquake to happen.
You well know by now that at 5:04:15 p.m. and for fifteen seconds afterward, the San Andreas snapped, releasing the energy of 75 atom bombs. The shaking caused, in today's dollars, $14 billion worth of damage. The headlines in the Chronicle screamed "Hundreds Dead In Huge Quake", but miraculously, "only" 63 died. There were almost 4,000 reported injuries.
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The double-decker freeway leading to the Bay Bridge pancaked in precisely the section that had been built on landfill. The Marina was in flames. It was by the skin of their teeth that stretched to their limit firefighters were barely able to prevent all the pricey housing from turning to ash as so many buildings had in the great 1906 quake.
The area shook like a bowlful of jelly, the district having been a former lagoon, filled in with the cinders and debris left behind by the earthquake that struck 82 years earlier.
At Beach and Divisadero, an entire building went up in flames. A section fell out of the old deck and truss section of the Bay Bridge. It was sheer luck that the quake happened as the San Francisco Giants were playing the Oakland A's in Game 3 of the Bay Bridge World Series at Candlestick Park. By 5 p.m., many fans were already off the roads and parked in front of their television sets to watch the game.
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Many were soon to be treated to the sight of the underside of their dining room tables as thousands of houses pitched and rolled. The game was literally a life-saver. Hundreds more could possibly have died had they been in the wrong place at the wrong time on the usually-packed Cypress Street viaduct on the Nimitz freeway.
In San Francisco, five people were killed on 6th Street between Bluxome and Townsend when a brick façade collapsed onto a sidewalk. In Hollister, my grandmother's house -- sitting on an 1870 mud sill foundation fashioned out of old-growth 2x6 redwood planks some 20 miles from the epicenter -- rocked and rolled and emerged entirely intact, just as it had after the 1906 quake.
San Francisco and Oakland, at 40 miles distant, suffered damage from what was for those two cities a distant epicenter. The national media quite incorrectly reported it as a "San Francisco earthquake." It was not. It was a far worse earthquake for Santa Cruz and Watsonville, with much of their downtowns reduced to shambles.
For the region's metropolitan areas, it was a seismic shot across the bow and a reminder of the intense activity of the San Andreas Fault system of the 19th century. An indication it had awakened after a decades-long quiescence following the massive stress relief of the 1906 quake.
And in 2023, Loma Prieta stands as reminder to us all that, the further away we are from the last big quake, the nearer we are to the next.
