Earthquake

If you haven’t felt the ground shake, you just haven’t lived in California long enough.

Belvedere is surrounded by 32 known fault lines – including some of the country’s most dangerous – any of which could rupture without warning. USGS estimates that there is a 72% chance that the San Francisco Area will experience an earthquake of at least 6.7 magnitude in the next 30 years (see table below).

Most of our houses in Belvedere are seismically sound. Our levees are not. Both Beach Road and San Rafael Avenue are built atop Bay mud and sand, not the rock that is more typical of our region. During an earthquake, sand liquefies and mud compresses. Our engineering consultants estimate that our levees will displace by between 2 and 10 feet following a 7.0 magnitude earthquake at the San Andreas Fault.

Access to Belvedere, including by our first responders, could become challenging. Furthermore, the rigid steel and clay water pipes that run under our levees would likely rupture, making it impossible to fight the fires that invariably follow major quakes, as residential gas lines break. Our unstable levees pose great risk to our City.

Thankfully, there are solutions. Sheet piling Beach Road and San Rafael Avenue – i.e. driving interlocking steel sheets into the ocean bed on the exterior of the two levees – would dramatically reduce displacement to within a few inches.

userEarthquake