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 really 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, which lasted about 60 seconds, 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 since then have been less severe. 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 the design and structure of buildings as well as the local soil in which they were built upon. 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. From this body of knowledge, engineers have learned that thousands of older buildings in major cities on fault lines still need retrofitting. Soft-story apartment complexes are particularly at risk since they tend to have soft stories (Tuck Under parking), which is a result of building designs that were thought to be sufficient.
A seismic retrofit can be done in various ways, depending on the existing structure. The common thread among these methods is to provide reinforcement to strengthen the structure. The process begins with a structural inspection to detect how the building will perform in an earthquake.
The best way to protect your building from damage, injuries and lawsuits that may result from an earthquake is to hire seismic specialists. Contact us at Saunders Construction to learn more about making your building safer. We have been in business since 1979 serving California, Washington and Oregon.