Geology of the Santa Clarita Valley – Earthquakes

There have been many earthquakes in recent history that have affected the Santa Clarita Valley. This timeline make it easier to see when and where they happened and how they affected this valley. Mx.x means Magnitude x.x. Numbers in parenthesis refer to footnotes at end of timeline.

January 9, 1857 – Parkfield/Fort Tejon/Wrightwood M8.2 (1)

The quake occurred on the San Andreas Fault. The epicenter of this earthquake may have been in the Cholame Valley, south of Parkfield. State Highway 46 passed through the valley today. Damage from this quake was widespread. Most of California shook during this earthquake as it was felt from Marysville to Mexico. Tulare Lake was shaken out of its bed causing flooding on the lake edge. The Kern River near the present day town of Bakersfield was forced out of its banks and caused flooding for many miles. Many buildings in the Los Angeles area suffered heavy damage as well. Ft. Tejon was also severely damaged in this quake. Slippage along the fault was about 30 feet along the fault north of the Fort Tejon area and about 15 feet south of the Fort Tejon area. The total length of slippage was over 200 miles. Only two persons died in this earthquake, mostly due to the low population in Southern California at the time.

April 2, 1893 – Pico Canyon M6? (1)

The fault on which this quake occurred is unknown. It may have been from the Santa Susana Thrust Zone located along the southern boundary of the Santa Susana Mountains. Damage was localized to Mentryville (2) and there were only landslides most everywhere else.

July 21, 1952 – Arvin/Tehachapi M7.0

This was located on the White Wolf Fault (WWF) near Grapevine. Wheeler Ridge, an anticlinal ridge located also near Grapevine, rose with no surface ruptures. The WWF, on the other hand, had many surface ruptures. This earthquake may have actually been a folding event. Gas and water mains broke in Los Angeles along with some power lines. The town of Tehachapi was devastated by the quake. Many of the buildings collapsed or had large sections fall as a result of the quake.

February 9, 1971 – Sylmar/San Fernando M6.5

The epicenter of this disastrous earthquake was about 1 mile southeast of the intersection of Soledad Canyon Road and Sand Canyon Road in Canyon Country (34d 25′ N, 118d 24′ W) on the Sierra Madre Fault Zone, a north-dipping reverse fault on the south side of the San Gabriel Mountains. The ground movement was about 2 meters of offset, primarily vertical, with some left-lateral motion as well. It ruptured the ground surface for about 15 km, caused 64 deaths, and $511 million in damages. Most of the deaths were caused when the Veterans Hospital in Sylmar collapsed. There were surface ruptures along the base of the San Gabriel Mountains. The old Swall Block at Market and San Fernando in Newhall had to be torn down due to extensive damage. It was built in 1919. Local freeways also suffered greatly as the incomplete I-5/SR-14 interchange collapsed along with the I-5/I-210 and I-5/I-405 interchanges.

January 17, 1994 – Reseda/Northridge M6.8

The blind thrust fault that this quake originated from was relatively unknown until that morning. Damages totaled to over $10 billion dollars. It was centered in under Reseda near Saticoy St and Corbin Ave but the damage was greater in Northridge. This quake was preceded by two swarms of quakes. One in Santa Monica and another near Castaic Junction along the Holser Fault. The I-5/SR-14 interchange collapsed yet again only this time it was not under construction at the time. An LAPD officer was killed crossing the collapsed interchange, albeit about an hour after the earthquake. His name was Clarence Wayne Dean (3). Local damage ranged from complete collapse of the structure to collapsed chimneys. Hart High school suffered the most damage of all the local schools. Its 48 year old gym had to be demolished because of the damage. It has since been rebuilt. The auditorium also had to be closed for the same reason. Most of the aftershocks from this quake have been located in the Santa Susana Mountains, which are just south of the Santa Clarita Valley. Some uplift and cracking ocurred along Stevenson Ranch Pkwy, creating the bumps that are in the road even today. An oil pipeline near Edison Curve also broke, leaking many hundreds of gallons of crude oil into the Santa Clara River. Another break occurred along McBean Pkwy near Valencia Blvd. The Los Angeles Aqueduct siphon south of Soledad Canyon Road also cracked, sending a spray of water visible from the road.

(1) estimated from damage and intensity; magnitude scale did not yet exist

(2) located in Pico Canyon. Some remains exist today.

(3) interchange later named the Clarence Wayne Dean Memorial Interchange

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