Sylmar Earthquake 1971 • Anniversary TODAY 55 years later

The biggest seismic jolt in 80 years struck the northeast San Fernando Valley before dawn — flattening freeway overpasses, collapsing hospitals, toppling power stations, sparking fires and threatening to burst dams and flood the homes of tens of thousands.

When the dust cleared on the 1971 Sylmar-San Fernando earthquake 45 years ago Tuesday, 64 people lay dead and more than 2,500 lay injured beneath more than $550 million in rubble.

The 12-second temblor, at 6.6 magnitude, ripped along a 12-mile fault zone beneath the San Gabriel Mountains beginning at 6:01 a.m.

Thousands awoke to topsy-turvy homes and businesses. But the biggest to bear the brunt was the San Fernando Veterans Administration Hospital in Sylmar, whose unreinforced concrete wings built in 1926 collapsed, killing at least 44.

That’s where nurse Betty Van Decar had just signed off on a night shift when she saw Ward 5 and its inhabitants vanish into a cold dark morning.

“It buckled down, caved in, the whole building, Van Decar, 83, of Granada Hills, told the Daily News a decade ago. “There was an awful sound — you could hear the ground rumbling. I thought: They’re not going to make it.”

The 1971 Sylmar quake — dubbed the San Fernando earthquake by scientists and the biggest shaker to date in Los Angeles history — spread death and destruction as far as downtown.

Freeways buckled. Sewer lines broke. Gas lines exploded. Power lines fell, telephone service cut. Chimneys toppled. Windows shattered. Dams threatened to burst. And thousands of homes, businesses, hospitals and government agencies were turned upside down.

It was then the state’s third worst earthquake in terms of lives lost, only exceeded by San Francisco in 1906 and Long Beach in 1933, and the second in terms of property damage, according to seismologists. Of the 64 deaths — the estimates vary — nine were attributed to heart attacks.

It was also the worst earthquake to befall the Valley since an 1893 quake near Newhall.

The intense shaking crumbled a six-story, newly opened psychiatric ward at the county’s Olive View Community Hospital in Sylmar, killing three. Despite the ruin, nearly 1,000 patients and staff were safely evacuated.

Three other hospitals, including the VA, suffered severe damage, as did a $110 million electrical switching station, San Fernando juvenile facility and a glass factory in Newhall.

At least a dozen bridges fell onto freeway lanes, including the overpass at Interstate 5 and the 210 Freeway, killing two. A recently completed Newhall Pass interchange at I-5 and Highway 14 collapsed (the same overpass that also failed 23 years later during the 6.7-magnitude Northridge earthquake).

The lower dam at the Van Norman reservoir near the L.A. Aqueduct threatened to burst, spilling 3.6 billion gallons of water into nearby Granada and Mission hills. More than 80,000 people below the dam were evacuated for three days while engineers toiled to pump out its water.

If the earthquake had struck a year earlier, engineers later said, the dam topped with 6.5 billion gallons of water would have likely collapsed, killing more than 100,000 Valley residents.

After the quake, residents were forced to endure without water, gas and power for weeks as the Salvation Army rolled out trucks of hot food.

“We had camping gear, with canteens and stoves, for five weeks,” John Brooks, 75, of Sylmar, a San Fernando reserve officer and security guard who was initially knocked out when three rifles fell off the wall and whacked his head, had told the Daily News. “I know of some families that ran out of their homes as bare as the day they were born.”

The 1971 Sylmar earthquake — a precursor to the ‘94 Northridge quake — would trigger a slough of new safety standards for hospitals, dams, freeways and land-use planning across the state.

Today, there are but few reminders of the giant tremor so violent it swayed a forest of new high-rise buildings downtown — reportedly killing two in the falling rubble of old buildings — and damaging churches as far away as Pasadena.

At Veterans Park in Sylmar, rock walls appear to be the only trace of the giant VA complex that once served tubercular veterans.

Only a “Lest We Forget” plaque serves as a reminder of the dozens lost during the long-ago quake.