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Understanding Seismic Retrofit in California

Several earthquakes have shaken both San Francisco and Los Angeles in 2019, which is a reminder that old building owners need to consider a seismic retrofit solution for California. Not only is California one of the most vulnerable states for seismic activity, many older buildings lack modern design to provide sufficient safety. Here are reasons why old building owners need to take retrofit seriously in the Golden State.

Why California Shakes so Much

Every year, Southern California experiences around 10,000 earthquakes, according to the US Geological Survey (USGS). Since these quakes are usually minor with a magnitude under 3.0, most people don’t even notice them. A large earthquake, however, can cause massive damage, deaths and a series of aftershocks. While most states have earthquakes, with Alaska having the most regular seismic activity, California also ranks among the highest for potentially powerful earthquakes.

Knowledge about why earthquakes occur goes back to the 18th century, when it was determined that they are caused by shifts in rock mass miles beneath the surface of the earth. Most earthquakes develop in fault lines, which are fractures in the earth’s crust, allowing giant plates to crush into each other. The San Andreas Fault runs along the western side of most of California. Even though it’s often thought of as one long fault, it’s composed of multiple segments over a stretch of 800 miles.

Many people assume that the earthquake of 1906 in San Francisco was the worst in American history, but it actually didn’t make the top 15. It was mainly the fire afterward that caused the most destruction. The 1964 quake in Alaska is the most severe on record with a 9.2 magnitude. California’s worst quakes were:

  • 1857 (Fort Tejon, 7.9)
  • 1872 (Owens Valley, 7.8)
  • 1892 (Imperial Valley, 7.8)
  • 1906 (San Francisco, 7.7)
  • 1992 (Landers, 7.6)
  • 1927 (West of Lompoc, 7.3)

The Loma Prieta earthquake of 1989 had a magnitude of 6.9, causing major damage in San Francisco, killing 62 and injuring over 3,700 people. The Northridge earthquake of 1994 that shook Southern California measured 6.7, leading to 60 deaths and 7,000 injuries. Scientists predict the state is due for another major earthquake by 2030.

Seismic Retrofit as a Protective Solution

One of the reasons so many people have been killed or injured by big earthquakes is they were in buildings that were not designed to today’s standards. It wasn’t until the late 1990s when building codes for construction designed to resist seismic activity were initiated. That means any older building is a candidate for retrofit, especially if it was built prior to 1992, when modern engineering theories began to be integrated into construction. Remember that building owners can be held responsible for unsafe conditions.


Every owner of old buildings should at least talk to a seismic retrofit contractor to find out if the building does need a retrofit. It will give you a clear indication as to whether the building can withstand a major earthquake. Contact us at Saunders Commercial Seismic Retrofit to ensure your building is safe or can be made safer.

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