Over the years Union City has experienced a number of earthquakes, with three quakes being significant enough to go in the record books.

1868 - Hayward Fault

The first earthquake to hit the Union City area was in 1868. This quake occurred at 7:45 AM on Wednesday, Oct. 21 and was of magnitude 7.0. The quake was on the Hayward Fault. This was the quake the destroyed most of Mission San Jose. Since there were few buildings in Union City at the time, there was very little damage in Alvarado or Decoto. The only buildings damages were a brick shop and a store. The quake was felt as far way as Sacramento and Virginia City, Nevada.

1906 - San Andreas Fault

As much as the 1906 earthquake is associated with San Francisco, the quake affected the entire Bay Area, including the Union City area. The most damage from the quake was suffered by the Alavarado Sugar Company beet-sugar plant (later to become Holly Sugar).

1989 - Loma Prieta

Compared to the other earthquakes and compared to the damage in San Francisco or Oakland, Union City was pretty much unscathed by this quake.

Earthquake Maps

The Association of Bay Area Governments (ABAG) has created a number of earthquakes maps that give an idea of the level of shaking that would take place for a given quake. These maps include the shaking that took place in the 1906 and 1989 earthquakes. They also show maps for forecasted quakes, including a 6.9 on the Hayward Fault that shows what the 1868 quake was like.

1868

1906

1989