On October 17, 1989, at 5:04:15 p.m., a 6.9 magnitude earthquake shook the San Francisco Bay Area. The epicenter was located in the Forest of Nisene Marks State Park in the Santa Cruz Mountains. As documented by the U.S. Geological Survey (USGS), "This major earthquake caused 63 deaths, 3,757 injuries, and an estimated $6 billion in property damage. It was the largest earthquake to occur on the San Andreas fault since the Great San Francisco Earthquake in April 1906."
The harrowing break in the Bay Bridge, images of collapsed buildings, images of raging fire in the Marina District, and the cars crushed and people trapped by the collapse in Oakland of the Cypress Street Viaduct were for weeks grim reminders of the havoc wrought in 15 seconds.
The USGS reported on the role of liquefaction in the damage, noting that "Subsurface soil conditions, which amplified accelerations in the San Francisco Bay area, strongly influenced structural damage patterns and probably contributed to liquefaction problems in loose, sandy fills underlain by deep, cohesive soil deposits."
