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State Study Depicts Horror of Inevitable Quake On Hayward Fault

August 13, 1986

LOS ANGELES (AP) _ Up to 4,500 deaths and 148,500 injuries could result when buildings collapse or burn during a major earthquake that inevitably will strike the Hayward Fault east of San Francisco Bay, a study says.

Such a temblor ″would constitute one of the most devastating natural disasters that could conceivably strike this nation,″ said a summary of the 220-page report by California’s Division of Mines and Geology.

The report said plausible consequences of a Hayward Fault temblor measuring 7.5 on the Richter scale include power blackouts; natural gas fires; ruptured water, sewer and petroleum pipelines; overloaded telephones; blocked freeways and railroads; closures of ports, bridges and refineries, and damage to runways at San Francisco, Oakland, Hayward and Alameda airports.

The catastrophic quake would pose ″a major threat to the entire Bay area,″ but the famed Golden Gate Bridge and the subway tunnel under the Bay would survive, said the summary published in the latest issue of the division’s California Geology magazine.

State geologist Jim Davis, who heads the division, said Tuesday the worst destruction would occur in a 5-mile-wide swath near the fault in the East Bay area, including parts of Berkeley, Oakland, Hayward, Fremont and eastern San Jose.

In that area, powerful shaking would cause considerable damage to supposedly quake-resistant buildings and partly collapse others, the report said.

It added that shaking would be strong enough to cause considerable damage to ordinary buildings and great damage to poorly built structures throughout the Bay area, from Napa Valley and Marin County through San Francisco and the East Bay, and south to San Jose, including the high-technology Silicon Valley.

The study said a 7.5-magnitude Hayward Fault quake could kill 1,500 to 4,500 people, put another 4,500 to 13,500 people in the hospital and cause 45,000 to 135,000 injuries not requiring hospitalization.

The fault caused house-wrecking magnitude-7 earthquakes in 1836 and 1868, the report said, adding, ″Future earthquakes of comparable magnitude (6.5 to 7.5) are a reasonable expectation and could occur at any time.″

″There is no question there will be an earthquake of that size range in the future,″ probably within the lifetimes of many Bay-area residents, but it is impossible to say exactly when, Davis said in a telephone interview from Sacramento.

He emphasized the report describes plausible worst case results of a major Hayward quake and is meant to spur improvements to protect buildings and utility lifelines and to encourage detailed disaster response plans.

The report, issued without fanfare two weeks ago, is the third in a series outlining consequences of disastrous temblors in California. Twin 1982 reports listed damage expected from magnitude-8 quakes on the southern and northern San Andreas Fault. Such quakes would be repeats of the great quakes in Southern California in 1857 and San Francisco in 1906.

The 62-mile Hayward Fault runs from San Pablo southeast to Mount Misery, east of San Jose.

The Richter scale is a measure of ground motion as recorded on seismographs. Every increase of one number means a tenfold increase in magnitude. Thus a reading of 7.5 reflects an earthquake 10 times stronger than one of 6.5.

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