Abstract This volume consists of twenty field guides that were created to cover the diverse interests of the 100th Anniversary Conference held in San Francisco, California, to mark the centennial of the 1906 San Francisco earthquake. The guides presented here represent the interests of earth scientists, engineers, and emergency planners, and reflect the cooperation between the Seismological Society of America, the Earthquake Engineering Research Institute, and the California Governor's Office of Emergency Services, the three organizations that jointly organized this unique conference. The field guides are specifically intended to cross the boundaries between these organizations and to be accessible to the general public. The locations of most of the field trips are shown on Figure 1 , which shows the San Francisco Bay area as photographed from the International Space Station. However, the area shown on this figure is not big enough to include all of the trips: Chapters 11, 16, 19, and 20 spill over to the north, south, and east of the region shown in the figure. The geology of California is the direct result of the action of plate tectonics. Earth's crust is composed of six major (and many smaller) plates that are in constant motion with respect to each other. There are three kinds of boundaries between these plates: (1) divergent boundaries, where plates move apart, material wells up from Earth's interior, and new crust is created; these boundaries lie mostly along Earth's major mid-oceanic ridges; (2) convergent boundaries, or subduction zones, where plates collide and