Open Thread for Thursday

The Sylmar earthquake struck at 6:00:55 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.

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.

The most spectacular damage included the collapse of structures at Olive View Hospital in Sylmar (which had opened just a month prior to the eqarhquake) and at the Veterans Administration Hospital at San Fernando, where 49 people died. The earthquake pushed Olive View Medical Center a foot off its foundation, causing the first floor to collapse, killing three patients and a hospital worker. A freeway overpass connecting the Interstate 5 freeway and the Antelope Valley Freeway (California State Route 14) also collapsed, which restuled in the death of at least two people. (This interchange was rebuilt and reopened in 1973, but ironically collapsed 23 years later during the 1994 Northridge Earthquake, killing one.)

Link to text from Herald-Examiner article at the time, onthe LA Fire Department website.