1989 Loma Prieta (Santa Cruz)
This scenario is similar to the 1989 Loma Prieta earthquake in its effect. That earthquake did not rupture the San Andreas fault itself, but instead ruptured a 40 km long fault near the San Andreas in the Santa Cruz mountains. This scenario assumes that the San Andreas fault itself is the segment that ruptures, but the resulting earthquake is about the same size and in about the same place as the 1989 earthquake experienced by the San Francisco Bay Area.

Concord/Green Valley fault system
The Concord fault and Green Valley fault are two individual segments that connect up across the Suisun portion of the San Francisco Bay. The segments go by different names because they are on different sides of the Bay. In this scenario, the two segments rupture together in one larger earthquake. No such earthquake has occured since we have historical records, but the fault is an important part of the plate boundary system. It has been accumulating strain for some time, though its rate of strain accumulation is lower than many of the other faults in the system.

Hayward fault
In this scenario, the entire length of the Hayward fault (including both northern and southern segments) ruptures. This rupture is about 85 km long, though the exact length is unknown because the Hayward fault runs offshore and underwater into the San Pablo section of the San Francisco Bay. Underwater portions of faults can be much harder to study because they can't be observed as easily. The only major earthquake on the Hayward fault that has occurred since we've had historical records was in 1868. That earthquake ruptured only the southern segment of the Hayward fault, but was extremely damaging. Locals referred to it as the "Great San Francisco Earthquake" until the 1906 earthquake, a much larger earthquake, took over that title.

The four earthquake scenarios listed above refer to the effects of a specific earthquake scenario on a specific fault with a known magnitude. In the liquefaction map, we focus only on the properties of the soil and do not include distance from the fault. An area that has high liquefaction susceptibility but never experiences strong ground shaking won't have any problems. For example, there might be areas of high liquefaction susceptibility in Kansas, but because earthquakes are so rare there, there is very little danger from liquefaction. In other words, an area is only at risk of liquefaction if it shows up as red in BOTH the ground shaking map AND the liquefaction susceptibility map.