Geologically Active - The 1971 Sylmar Quake & 1994 Northridge Quake

The Widowers’ Benches are located at the eastern end of the San Gabriel Mountains and the Western end of the Santa Susana Mountains. This region is geologically very active. The San Fernando Fault Zone consists of five major segments, that display reverse-left-oblique movement. The San Fernando Fault Zone forms the frontal system of the San Gabriel Mountains. This fault systewasmost recently active during the 1971 San Fernando (Sylmar) Earthquake, which produced a Richter magnitude 6.6 earthquake. The Santa Susana Fault Zone consists of several individual fault segments that extend from the Santa Susana Mountains across the San Fernando Pass and into the San Gabriel Mountains. Some geologists believe that sympathetic movement occurred along the fault system during the 1971 San Fernando Earthquake. Both Roberta Herr and Cheryl Morgan, for whom this website is dedicated,as well as their husbands, clearly recalled the 1971 Sylmar and 1994 Northridge Earthquakes which rocked this region. The 1971 Sylmar earthquake (also known as the San Fernando earthquake) struck the San Fernando Valley at 6:00 AM on February 9, 1971 and la

sted approximately 60 seconds. The epicenter for the quake was in Iron Canyon, in the Sand Canyon area near the Sand Canyon Road that leads to the Bear Divide Trail. The earthquake caused numerous surface ruptures with average displacements of about 3 feet both horizontally and vertically over a region extending more than ten miles. Sixty-five people lost their lives in the earthquake, 49 of whom were at the Veterans’ Administration Hospital which is now Veterans Memorial Park in Sylmar which is the trailhead for the May Canyon trail that leads to the Wilson Canyon bench. In addition, the earthquake pushed Olive View Medical Center off its foundation, causing the first floor to collapse, killing four people. The New UCLA Olive View Medical Center is built on the site of the damaged hospital and is the trailhead for the Wilson Canyon trail that leads to the May Canyon bench. In addition, the Sylmar quake destroyed the Newhall Pass interchange connecting Interstate 5 and the Antelope Valley Freeway. This interchange was rebuilt in 1973 but destroyed again in the 1994 Northridge earthquake.

The Northridge earthquake struck at 4:31 AM, on January 17, 1994. The earthquake registered 6.7 on the Richter Scale. The ground acceleration measured 1.7g, one of the strongest every recorded in an urban region. The earthquake occurred on the previously undiscovered Northridge blind thrust fault. The Northridge earthquake damaged the Golden State (5) and Antelope Valley (14) Freeways. The most spectacular damage occurred at Gavin Canyon near the Weldon Canyon and East Canyon trailheads that lead to the Mission Peak bench.