The Golden Gate Bridge

Studying Earthquakes, Saving Lives

Henry Degenkolb
Henry Degenkolb doing EQ reconnaissance work
In 1952 Henry Degenkolb, one of the major figures in Structural Engineering, had been designing buildings for more than 15 years to withstand earthquakes but had never seen one. He decided that wasn't good enough. So he visited Tehachapi in Kern County, the site of a quake in 1952, launching his quest and that of other engineers for firsthand knowledge. "People who chase earthquakes, instead of reading a report and looking at pictures - they see the damage and the lives lost. That's largely what determines their attitudes." Go to Some of our Icons/Heroes for more information about Henry Degenkolb and other celebrated Structural Engineers.

For the last 50 years, Structural Engineers from the Bay Area have made it a practice to visit the site of every major earthquake to learn firsthand from their effect on buildings and other structures. Earthquake sites, in short, have become the laboratories for the Structural Engineer. Go to Developing Codes and Standards for Safer Structures for more information on new codes and standards that were developed following historic earthquakes.

Old St. Mary's Church in Chinatown, after the 1906 Earthquake
One of the most important discoveries that Structural Engineers have made in the past 50 years is that earthquakes can cause a wide variation in the ground motion even in building sites in close proximity. In other words, the ground acceleration can differ from one parcel to another, creating a kind of randomness in the degree of damage caused to buildings in the same vicinity.

In other words, an earthquake may knock all buildings down except one on any given block in San Francisco. The remaining building could have survived for a variety of reasons involving the type of ground, the ground motion and the quality of the structure.

Structural Engineers visit sites of
earthquakes such as in Guam in 1993.
When determining the quality of a building's safety, therefore, Structural Engineers cannot guarantee its condition simply by reviewing its performance in any given earthquake. Just because a building survived the 1906 or a more recent earthquake, for example, does not mean it is earthquake-resistant today. In 1989, in the Marina section of San Francisco, for example, some buildings survived the Loma Prieta earthquake but there is no technical explanation why this occurred.

Structural Engineers know for sure when a building will not survive based on their analysis and observation of a building's structure, material, and age. And they know what needs to be done to build a safe structure and retrofit an older one. But when earthquakes hit, and at-risk buildings are not affected, Structural Engineers know it's the randomness of the earthquake at work.