40 Years Ago Today: San Fernando Earthquake Topples Freeways & Prompts Seismic Retrofitting Plan

Forty years ago today, at 6:01 a.m., an earthquake near San Fernando measuring 6.6 on the Richter scale rolled across Southern California, leaving at least 65 dead and staggering structural damage.

I-5 & Route 14 Interchange, February 9, 1971

While the Northridge Earthquake of 1994 is the largest shaker in recent memory — and still fresh in many people’s minds — the San Fernando (or “Sylmar”) quake shocked Southern California in terms of the its wide-scale destruction.

Several wings of Olive View Hospital collapsed on their sides just one month after it opened and forty-nine people perished in the collapse of the Veterans Administration Hospital in San Fernando.  Two area dams were severely compromised.

With the collapse of several freeway overpasses, transportation was critically disrupted.  According to The Race To Seismic Safety: Protecting California’s Transportation System (186p. PDF):

Before the 1971 San Fernando Earthquake (early media reports refer to this event as the “Sylmar Earthquake” while seismologists use the name “San Fernando Earthquake”), it was assumed that operational loads on bridges presented more severe structural requirements for bridges than did earthquakes.

[The earthquake] dramatically illustrated the error of this assumption and the public paid for the consequences in out-of-service roadways.

Following the San Fernando Earthquake, there was a concerted effort to retrofit bridges, but the resolve eventually diminished.  While the interest of Caltrans remained strong, the resources were unavailable.

Twelve overpass bridges fell onto freeway lanes, including the I-5 interchange at the 210 Freeway which resulted in two deaths.

A freeway overpass at the recently completed Newhall Pass interchange of the I-5 and Antelope Valley freeways also failed.

(The interchange was completely rebuilt and reopened in 1973, only to collapse again in the 1994 Northridge earthquake)

One outcome of the San Fernando earthquake was the creation of Caltrans’ Seismic Retrofit Program.  Since the 1971 quake, Caltrans has been engaged in an ongoing bridge seismic safety retrofit program.

The Department’s current Seismic Safety Retrofit Program was established following the 1989 Loma Prieta earthquake to identify and strengthen bridges that needed to be brought up to seismic safety standards.

A Seismic Safety Board of external engineering and scientific experts advises Caltrans on seismic safety policies, standards and technical practices.

Peer review panels of independent seismic and structural experts also are utilized to review earthquake-strengthening strategies on major, complex retrofit projects.

Newhall Pass Interchange collapse.

The first phase of the program identified 1,039 state highway bridges in need of being retrofitted to meet current safety standards.

The structures identfied in Phase 1 consisted of mostly single-column bridges that were most vulnerable.  Their retrofitting was completed in May, 2000 at a cost of $1.082 billion, funded by state gas taxes.

After the 1994 quake, Caltrans identifed another 1,155 state-owned bridges in need of retrofit.  These Phase 2 structures consisted mostly of multi-column bridges.  Bringing them up to current seismic safety standards is nearly complete.  The $1.35 billion price tag has been funded by State Proposition 192, passed in 1996.

Aerial photo of freeway damage, 1971 earthquake

Following the 1971 earthquake, Caltrans also implemented new bridge design criteria to make our highway infrastructure safer.

Additional resources:

Caltrans Office Of Earthquake Engineering

Caltrans Seismic Research Reports

Caltrans Seismic Design Criteria

Closing The Gap: In The Race To Seismic Safety (May, 2010 : 72p. PDF)

Competing Against Time: Report To Governor George Deukmejian From The Governor’s Board Of Inquiry On The 1989 Loma Prieta Earthquake (May, 1990 : 275p. PDF)