This is the second part in The Source’s new series called “Subway Facts & History” to address some of the issues generating discussion involving the Westside Subway Extension project. The facts below are based on information from Metro staff and consultants planning the project. The information, in various forms, has already been publicly released. 

One of the complications of planning any major project in greater Los Angeles is dealing with the fact that we live in earthquake country — as the above map shows. It’s one thing to build something so that it will be safe when the ground shakes in an earthquake. It’s quite another thing to build for earthquake safety when you are sitting directly atop an active fault.

The issue for the Westside Subway Extension is the presence of the active Santa Monica Fault in the Century City area where it runs beneath Santa Monica Boulevard. The location of the fault has two potential impacts: It could affect where the Century City station is built, as well as the location and orientation of the tunnels in that area.

Two basic routes for the subway between western Beverly Hills and Century City are being studied as part of the project’s Final Environmental Impact Statement/Report. One route would run under Santa Monica Boulevard to reach a station under that street. The other would run south of there and go under parts of the Beverly Hills High School campus to reach a station beneath Constellation Boulevard.

Here are some facts:

•As part of the environmental impact studies for the Westside Subway Extension, Metro is conducting geotechnical field tests to learn more about seismic characteristics in the Beverly Hills, Century City & Westwood areas

•A strand of the Santa Monica Fault appears to extend under the Los Angeles Country Club and beneath Santa Monica Boulevard from somewhere between Century Park East and Avenue of the Stars and extending west until it begins to turn away from Santa Monica Boulevard somewhere near Westwood Boulevard.

•In addition to the Santa Monica Fault, Metro is also trying to better understand another possible seismic feature, the West Beverly Hills Lineament, which runs north-south through the western part of Beverly Hills near the Beverly Hills High School.

•One way of reducing the risk from an earthquake is for the tunnels to cross the fault in a perpendicular manner rather than run parallel to it, thereby limiting the tunnel’s exposure to the fault.

•Subways can and have been built in earthquake zones around the world and in Los Angeles, although it often requires special engineering and special construction techniques. Special designs have been developed for subway tunnels to facilitate short, perpendicular crossings.

•No transit agencies in North America have built subway stations within known active fault zones.

•Another project being planned by Metro, the Crenshaw/LAX light rail line moved the location of the La Brea station planned for that line to avoid having it sit directly atop the Newport-Inglewood Fault.

•Subways have a solid history of surviving strong earthquakes. While there was significant damage throughout Santiago, Chile following the 8.8 magnitude quake in February 2010, their subway system was running within 2 days.

•Besides Santiago, some other earthquake-prone cities with subways are Tokyo, San Francisco, Mexico City and Istanbul.

•Metro’s Red Line tunnels withstood the 1994 Northridge earthquake without any damage.

•The Metro Red Line tunnels cross the Hollywood Fault, considered to be active, north of the Hollywood/Highland station. Special designs were employed where the tunnels cross that fault that allow it to better withstand an earthquake and, if needed, be more easily repaired.

•Last fall’s draft environmental impact statement/report for the subway included geotechnical information gathered up to that point.

•Further geotechnical analysis is being done along the entire nine-mile alignment that is currently being studied. That information will be released later this year.

•Once the Final EIS/EIR is released, and there is a period for public review, it will be considered by the Metro Board of Directors. They will decide whether to proceed and make decisions about the project, including the location of the Century City station.

•Assuming the project moves forward, additional geotechnical tests will be performed, including in the Century City area, as a part of further engineering for the project.

Related: Subway Facts & History, Part 1: Building atop subway tunnels