On the 10th anniversary of the Loma Prieta earthquake, UC Davis' 15-year-old geotechnical centrifuge continues to get a good workout as researchers from around the world use it to test their earthquake hypotheses. Current projects study the performance during earthquakes of foundations for bridges and buildings, slopes, earth retaining structures, ports and seawalls, according to Bruce Kutter, professor of civil and environmental engineering and director of the Center for Geotechnical Modeling. Kutter and colleagues Boris Jeremic, an assistant professor of civil and environmental engineering, and Dan Wilson, centrifuge research and facility manager, are using the centrifuge to test tire shreds as a lightweight fill material to be used behind bridge abutments or embankments. Although other states allow the use of tire-shred fill, the state of California doesn't because, among other reasons, no one knows how the material would behave in the earthquake, Kutter says. The centrifuge, the largest of its kind in the United States, consists of a testing table, capable of carrying loads of five tons, mounted on the end of a 30-foot-long arm. The assembly spins around at speeds up to 70 revolutions per minute, generating forces up to 50 times the force of gravity. When the desired speed is reached, the table is vibrated to simulate intense earthquake shaking.