Strengthening Buildings for a Catastrophic Earthquake
California, Oregon, and Washington are western states that have experienced plenty of seismic activity in the past century. The construction industry has learned from one catastrophic earthquake after another to develop retrofit strategies starting in the 1970s. However, it wasn’t until the late 1990s that these concepts became commonly integrated with new construction.
West Coast Seismic Activity
The worst of these quakes happened just before sunrise in San Francisco on April 18, 1906. This quake lasted about 60 seconds and could be felt from southern Oregon to Los Angeles. The quake was so strong it started fires and even moved the ground in Germany, over 9,000 kilometers away. Although about 700 deaths were reported, historians believe the total death toll may have been in the thousands.
The 1906 catastrophic earthquake in San Francisco measured an estimated 7.7-7.9 magnitude, but California quakes have been less severe since then. The 1989 Loma Prieta quake that shook San Francisco during the World Series measured 6.9, while the 1994 Northridge quake in Los Angeles had a magnitude of 6.7. Each of these disasters has taught engineers how to erect stronger structures.
Learning from Earthquake History
The first seismographs to measure earthquake strength and duration appeared in 1887 at places such as the University of California at Berkeley. The 1906 disaster led to a State Earthquake Investigation Commission funded by the Carnegie Institution of Washington to bring geological scientists together for analysis.
Two years later, the commission released the Lawson report, which contained comprehensive data about the catastrophic earthquake. The report revealed that much of the damage was the result of buildings’ design and structure as well as the local soil. This report spawned the “theory of elastic rebound.”
How to Protect Buildings from Earthquakes
History has taught us that structures built on soft or weak foundations don’t hold up very well in major earthquakes. Engineers have learned from this knowledge that thousands of older buildings on fault lines in major cities still need retrofitting. Soft-story apartment complexes are particularly at risk since they tend to have soft stories (tuck under parking), resulting from building designs that were thought to be sufficient.
Depending on the existing structure, a seismic retrofit can be done in various ways. The common thread among these methods is to reinforce and strengthen the structure. The process begins with a structural inspection to detect how the building will perform in an earthquake.
Conclusion
Hiring seismic specialists is the best way to protect your building from damage, injuries, and lawsuits that may result from an earthquake. Contact Saunders Seismic to learn more about making your building safer. We have been in business since 1979, serving California, Washington, Oregon, Nevada, and Utah.