1. The repetition of large earthquakes, with similar coseismic offsets along the Carrizo segment of San Andreas fault has been documented using geomorphic data. If correct, this observation suggests periodic recurrence of characteristic slip along earthquakes on the Carrizo segment. More recent paleoseismic work at the Bidart site, however, show that the time interval between such earthquakes are highly irregular (Table 1).

2. Timing of past earthquakes at the Bidart site, Carrizo Plain, California. The last two earthquakes, 185 7and event B, perhaps had similar displacement The three closely spaced events C, D, and E have unknown displacement.

3. Two end-member hypotheses 1) Assuming that the displacement per event is similar and the repeat times of the large events are irregular Either a substantial increase of strain accumulated within this period (i.e., 1218 to 1857 A.D.), or increased strain was stored prior to this earthquake cluster. 2)Alternatively, if the slip per event was not similar, then the strain accumulation between events was constant, which implies that events C, D, and E must has had smaller surface displacements. 3)Such departure from periodic behavior suggests that either slip per event or strain relief rates varies by a factor of three or more.

5. Earlier measurements of channel offsets near Wallace Creek suggested that the past three events had similar slips. Our recent mapping suggests a slightly different history.

6. The history of deposition, erosion and offset is substantially different from previous studies. Down-stream and offset from Channel C are an offset gully and 2 small offset alluvial fans. The gully is only about 20 cm deep and the two fans are only about 20 cm thick.

7. Map views of buried channels at the site. Many buried channels exist downstream from the fault.

8. Vertical cross-section parallel to the fault shows the relative locations of downstream and upstream channel bottoms at their intersection with the fault. Correlative thalwegs bear the same colored symbol. Downstream channel shapes and strata appear at an enlarged scale atop their thalwegs. Upstream channel shapes and strata appear within the ellipse.

9. Horizontal and vertical offsets of channel pairs derived from the data in Figure 4. The horizontal and vertical offset of each pair appears as a small black rectangle, the size of which indicates the error associated with each measurement. The magnitudes of dextral offset for the six discrete ruptures range from 1.4 to 8.0 meters, At least three and perhaps four are between 7.5 and 8.0 meters. The vertical component of slip is in all cases a small fraction of the dextral offset.

10. Recovered magnitudes of the six most recent offsets across the San Andreas fault at a paleoseismic site between San Francisco and Los Angeles. Three and perhaps four of the events are right-lateral dislocations of 7.5 to 8 meters, including its latest rupture, in 1857. The third and fourth offsets, however, are just 1.4 and 5.2 meters. These data do not support hypotheses of invariant slip through several earthquake cycles. But neither do they strengthen arguments that rupture magnitudes vary randomly. They do suggest appreciable regularity in fault rupture and the concept of an earthquake cycle. The predominance of offsets between 7.5 and 8 meters suggests that this section of the fault fails most typically with rupture lengths of at least several tens of kilometers.