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Earthquakes in Southern California

Earthquakes in Southern California

The many earthquakes in California are caused by the movement of massive chunks of the earth’s crust – the North American and Pacific plates.  The Pacific plate is moving northwest, scraping past the North American plate at a rate of approximately 2 inches every year.  Close to two-thirds of this movement occurs on the San Andreas Fault and several parallel faults (the Elsinore, San Jacinto, and Imperial faults.)   Through the course of time, these faults produce about half of the major earthquakes in Southern California, as well as many minor quakes.

The actual rate of plate movement along the San Andreas Fault is close to 1.3 inches each year. Based on that rate of movement, the Los Angeles City Hall is now nine feet closer to San Francisco than when it was built back in 1924.   With that information in mind, you can see that it took many millions of years of movement on the faults (earthquakes) to shape the present-day landscape of Southern California.

The last major earthquake along the Southern California section of the San Andreas Fault was back in 1857, and interestingly, there has not been a rupture of the fault along its southern end from San Bernardino to the Salton Sea since 1690.  That area of the fault continues to store an incredible amount of energy for some future earthquake – possibly “The Big One”.

There is no need to wait for a “Big One” to experience earthquakes up and down the Pacific Coast.  Southern California has hundreds of smaller earthquakes each year.  Some of that seismic activity may cause damage, but most are not even felt.  In fact, most of the seismic activity does not even happen on the major faults listed above. Earthquakes can occur almost everywhere in Southern California; there more than 300 other faults that can cause destructive earthquakes, not to mention countless other small faults.  This is mostly due to a major bend along the San Andreas Fault.  Where the fault bends, the North American and Pacific plates push into each other, compressing the earth’s crust into the mountains of Southern California and creating hundreds of additional faults.  These faults produce thousands of small earthquakes each year.

Commercial property owners, especially in the Southern California area,  need to understand earthquake science and the potential devastation that can occur with strong seismic activity.   When commercial buildings are not strong enough, incredible devastation is possible.  Avoiding major structural failure is entirely possible when the materials are not stressed beyond their capacity.  While building codes in California and other tremor-prone areas have improved over the last 20-25 years, many older properties remain vulnerable to strong seismic activity. Commercial buildings constructed prior to 1987 are not considered to be engineered well enough to tolerate the strain of earthquake activity.

It is important to remember that a structure that has been designed well can sustain a localized failure without the collapse of the entire structure.  Unfortunately, if a building was not initially designed to accomplish that, it must be retrofitted (properly anchored and reinforced). Understanding the geology of the West Coast and knowing that “The Big One” could occur sometime in the next 25-30 years gives commercial property owners much to think about.  Two questions quickly come to mind:  how prepared are you and your tenants and how can you determine if your commercial property needs to be strengthened through a retrofit process?   Both the age of the building and the type of building are typically considered when contemplating the need for an earthquake retrofit.

Having your building retrofitted and having any hazards removed is a primary aspect of earthquake preparation for both residential and commercial properties.  If your commercial property is located in the Los Angeles area, remember that it is much more affordable and safe to retrofit a building before an earthquake hits, rather than waiting to repair expensive damages or pay for liabilities after an earthquake occurs.  To get more information regarding earthquake retrofitting or to schedule an earthquake retrofit inspection, call Saunders Seismic Commercial Retrofit today!

Southern California Office

(949) 646-0034

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