The 1989 Loma Prieta Earthquake became a Natural Laboratory
The 1989 Loma Prieta Earthquake gave us a chance to see that seismic retrofits work by in an actual earthquake. An architect owned two turn-of-the-century houses in Santa Cruz that needed foundation bolts and cripple wall bracing. These houses were identical in every way: same year of construction, same builder, same materials, everything was the same. In 1988, the architect retrofitted one of them using the retrofit techniques described on this website. He bolted it to the foundation, strengthened the cripple walls, and installed shear transfer ties. He was preparing to retrofit the other house when: The Loma Prieta earthquake struck.
The un-retrofitted house slid off its foundation and sustained over two hundred thousand dollars of damage. The retrofitted house only had plaster cracks that were relatively inexpensive to repair. This house was fully habitable. Earthquakes always cause cracks in the drywall or plaster, but seismic retrofitting can make them extremely earthquake resistant.
Seismic Retrofitting is again Tested in the 1994 Northridge Earthquake
In another example in Los Angeles, Bill Clinton did a photo shoot in front of a retrofitted house which suffered minimal earthquake damage. This was in a neighborhood that suffered significant damage. After this he funded FEMA to give hundreds of millions of dollars to retrofit homes in Los Angeles.
Many people ask us if a house can be made earthquake proof. We can only say Yes! After the earthquake, while you are drinking a cup of coffee and watching the news, you will be glad you retrofitted your house and made it as earthquake proof in a way that only a good seismic retrofit can.