Sylmar earthquake

From Academic Kids

The Sylmar earthquake struck at 6:00 a.m. PST on the morning of February 9, 1971. The earthquake that rocked the northern San Fernando Valley, near Sylmar measured magnitude 6.6 on the Richter magnitude scale.

'Sylmar Quake' is the name initially given to the event by local media outlets because the worst damage was to the Olive View Medical Center located in Sylmar. Local veterans of 'the Sylmar Quake' commonly refer to this seismic event as the 'February Ninth' quake. Seismologists call it the San Fernando earthquake.

In actuality, the epicenter of the quake was located underground, roughly at the intersection of Kenya Street and Wilbur Avenue in the Los Angeles district of Northridge.

The earthquake ruptured a segment of the San Fernando fault zone, a set of north-dipping, high-angled reverse faults along the southeastern margin of the San Gabriel Mountains.

It caused more than 10 miles of discontinuous surface ruptures with average displacements of about 3 feet both horizontally and vertically. A strong aftershock sequence followed the main shock and included four quakes in the Magnitude 5 range.

The quake claimed 65 lives and caused more than half a billion dollars in damage, including the destruction of two hospitals, a freeway interchange and the Lower Van Norman Dam. Damage to the dam caused concern that the dam, of the Earthen Bulwark type, might collapse, in whole or in part.

Much confusion ensued as various agencies declared a need for mandatory evacuations, or voluntary evacuations of various portions of the San Fernando Valley below the dam, depending on which agency was consulted, and often the evacuees were not able to be informed of the status of an evacuationin a timely manner, often returning home just as the police arrived to notify them of a new evacuation order, or evacuating at a moment when officials decided not to evacuate. Communication was made difficult (this was before the cellular phone became ubiquitous) by disruption of telephone, water and electrical service.

The most spectacular damage included the collapse of structures at Olive View Hospital in Sylmar and the Veterans Administration Hospital at San Fernando, where 49 people died. A freeway overpass connecting the Interstate 5 freeway and the Antelope Valley Freeway (Californa State Highway 14) also collapsed resulting in the death of at least two people.

Landslides were widespread and caused extensive damage throughout the San Gabriel Mountains.

It is reported that Los Angeles experienced a brief spike in the birth rate, 8-10 months subsequent to the event. (After all, Valentine's Day was a mere 5 days after the temblor!)


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