Appendix I

In areas of broadly distributed extensional strain, the back-tilted edges of a wider than normal horst block may create a synclinal-horst basin. Three Neogene synclinal-horst basins are described from the southern Rio Grande rift and southern Transition Zone of southwestern New Mexico,USA

The spatial and temporal distribution of fault slip is a critical parameter in earthquake source models. Previous geomorphic and geologic studies of channel offset along the Carrizo section of the south central San Andreas Fault assumed that channels form more frequently than earthquakes occur and suggested that repeated large-slip earthquakes similar to the 1857 Fort Tejon earthquake illustrate typical fault behavior. We found that offset channels in the Carrizo Plain incised less frequently than they were offset by earthquakes.

Recommendations to the U.S. Geological Survey National Seismic Hazard Mapping Program for the 2014 Update of the National Seismic Hazard Maps

We document the precise sizes, but not the dates, of the six latest offsets across the San Andreas fault at Wallace Creek, California. Three and perhaps four of these, including the latest in 1857, show dextral offset of 7.5–8 m. The third and fourth offsets, however, are just 1.4 and 5.2 m. The predominance of similar offsets for the latest six events suggests that the fundamental properties of the fault system that control slip size do not vary greatly from event to event. The large offsets imply that ruptures involving this site are typically more than 200 km long.