Residents recall devastating temblor
1989 Loma Prieta Earthquake leaves damage in its wake
Published: Monday, October 28, 2013
Updated: Monday, October 28, 2013 19:10
With an epicenter 10 miles northeast of Santa Cruz, a 6.9 moment magnitude earthquake was emitted from near the peak of Loma Prieta in the Santa Cruz Mountains, 60 miles south-southeast of San Francisco, on Tuesday, Oct. 17, 1989.
The main shock occurred at 5:04 p.m. when a segment of the San Andreas Fault ruptured, half an hour before the third game of the “Battle of the Bay” World Series between the San Francisco Giants and Oakland A’s was scheduled to begin.
Due to the game, the Loma Prieta earthquake was the first major quake to ever be broadcast on live television.
The disaster resulted in 63 deaths, with 3,757 reported injuries and $6 billion worth of property damage, according to the United States Geological Survey (USGS).
Around 16,000 housing units were deemed uninhabitable after the tumult, including 13,000 in the San Francisco Bay region.
Dr. Tom Holzer, an engineering geologist for the USGS, said, “The Loma Prieta reawakened people’s notions of how devastating an earthquake can be.”
The collapse of the Cypress Street Viaduct in West Oakland resulted in 42 of the 63 deaths and was due to obsolete bridge models and a lack of anticipation for large weight loads during a seismic event, according to a USGS report.
Prior to the Loma Prieta quake, The Great San Francisco Earthquake of 1906 shook the Bay Area, proving to be one of the most damaging earthquakes in U.S. history at a magnitude of 7.8. Sometime during the 83 years that elapsed between the two disasters, Northern California residents got comfortable.
The lull in major earthquakes in the Bay Area had created a false sense of security until the Loma Prieta Earthquake, Dr. Holzer said.
California Geological Survey Public Information Officer Don Drysdale said the San Francisco Marina District saw a lot of damage during the 1989 quake due to the underlying soil reacting to liquefaction. Soil liquefaction is a process in which soil loses strength and stiffness in response to applied stress and causes it to behave like a liquid.
Holzer said that soft soil underneath the first floors of buildings around the Marina District collapsed and ignited the gas pipes once gas had started to leak.
“A lot of the collapses we saw were caused because of soft first story soil,” he said.
Drysdale said, “The ‘rule of thumb’ is that if it is (an earthquake) greater than 5.5 (magnitude) you will have structural damage, especially for older brick masonry that is not reinforced.”
Charlie Eadie, land use consultant for Hamilton-Swift Land Use, was the recovery plan project manager during Santa Cruz and Watsonville’s reconstruction efforts following the temblor.
He said the soft soil also, in combination with unreinforced masonry buildings, led to the many buildings collapsing in downtown Santa Cruz.
As a resident of Santa Cruz, Eadie remembers seeing brick houses in his neighborhood crumble during the earthquake.
“The brick housing didn’t have rebar so it shook to pieces and I saw a cloud of yellow dust rising. I knew that the other (like) buildings were falling down in downtown,” he said.
Six deaths were recorded in Santa Cruz and roughly 1 million square feet of office and commercial areas were impacted.
Drysdale said, “It wasn’t clear at first, but the real significance (of the Loma Prieta) to scientists was how much damage the seismic waves could cause at a distance, simply because of the soil type.”
Holzer agrees. “I think it was a surprise to seismologists to see how much damage was done from afar (due to) the soft soil, which amplified the shaking velocity,” he said.
Since Loma Prieta, the USGS has strengthened its system in order to operate and record an earthquake while one is occurring, Holzer said.
USGS Public Affairs Specialist Leslie Gordon, said, “As time passed, (the USGS) learned a lot and now we can closely look at how earthquakes shake. We lost power here at USGS at the time (of the Loma Prieta) and our networks were not on backup generators. But we have (generators) now and our network and monitoring is in much better shape.”
San Pablo resident Larry Hansen, who managed a Safeway where the San Pablo Library is currently located, was on his way outside to check on a pumpkin display in front of the store when the quake struck.
“I saw the windows flex and what were almost like waves ripple in the parking lot. People ran out of the store immediately,” Hansen said.
Hansen, now owner of the Grocery Outlet on 23rd Avenue in San Pablo, said that after closing the store for eight hours following the earthquake, people “panic bought” groceries and supplies once he reopened.
“There were no deliveries for two days so a lot of panic buying went on. People wanted what they wanted and if they could not get it, they would fight over it,” he said.
Hansen said he could imagine people rioting for food if another earthquake were to hit the Richmond and San Pablo area.
Holzer said, “Unfortunately we have the Hayward Fault right in a densely populated urban area. We still have a lot of old buildings and, as far as damages, you can be looking at tens of billions of dollars and thousands of fatalities.”