Where's the Hayward Fault?

Treasure Island and Yerba Buena Island - Hayward Fault Tour

Map of the Yerba Buena and Treasure Island area midspan on the Bay Bridge between San Fancisco and Oakland, California.

Map of the Yerba Buena and Treasure Island area mid span on the Bay Bridge between San Francisco and Oakland, California
Click here to continue the image tour, or click on map cameras to see selected photographs.

What to look for: Yerba Buena Island consists mostly of natural bedrock, whereas Treasure Island was constructed of landfill; the two islands are connected by a causeway. Treasure Island was created in 1939 for the Golden Gate International Exposition from fill dredged from the bay. A brief stop on the islands is recommended for field trips starting on the San Francisco Peninsula. From the islands it is easy to observe earthquake retrofit and replacement operations on the eastern span of the Bay Bridge. Views of the Bay Bridge (east and west spans), San Francisco, and the Bay are spectacular from the islands.

Because Treasure Island is built from fill, it experienced extensive liquefaction during the M 6.9 Loma Prieta earthquake of 1989—and it is expected to again in an anticipated Hayward Fault earthquake. Liquefaction occurs during earthquakes where shaking causes loosely consolidated sediments that are saturated with water to loose cohesion and become fluid. Once a zone of liquefaction occurs, it can cause the surrounding consolidated materials to shift or rupture. Sand, mud, and fluids can erupt on the surface along fissures. Areas of intense liquefaction can result in extreme damage to the landscape and any building and infrastructure built on it.

Access Options

Most of Yerba Buena and Treasure Islands belong to the U.S. Coast Guard and are inaccessible without permission. However, the exits on Interstate 80, about mid span on the Bay Bridge, are accessible to the public. Pull offs on the causeway to Treasure Island Road provide scenic vistas of the San Francisco Bay area (including views of the east and west extensions of the Bay Bridge). At the time of this writing, the eastern span of the Bay Bridge is under major earthquake retrofit construction.

BART and Muni Bus: The islands are served by a single Muni bus route—the 108 Treasure Island. The bus route connects to the Trans Bay Terminal at Mission between 1st Street and Fremont in San Francisco (between the Embarcadero and Montgomery Street BART Stations).

The islands are not accessible directly by bicycle from either San Francisco or the East Bay. Because most of the two islands are owned and managed by the U.S. Coast Guard, there is very limited access to places to bike, hike, or have wheelchair access.

Car: There are exits to Treasure Island on both directions on Interstate 80 about mid way across the Bay Bridge. Use caution when exiting and entering the highway.