Results also include the completion of the map of the ~1 Ma horizon (975 +/-75 Ka; Huftile and Yeats, 1995). The onshore part of the map was constructed from Yeats (1981 and 1989), and slightly modified by interpolation of additional contours. Depths from the offshore map and cross sections of Yeats (1981, 1983) were converted to travel time using velocity surveys in wells, and then correlated through a grid of 1970s-vintage multichannel industry seismic reflection data loaned to the project by Occidental Oil and Gas. Velocity surveys in numerous wells were used to convert the travel timesback to depth. These depths were combined with the depth contours of Yeats (1981), and a new map created. This map shows folding and reverse faulting along the Mid Channel and Oak Ridge trends, folding of the Ventura Avenue anticline, the steep fold limb above the blind San Cayetano fault, and the large vertical motions across the onshore Oak Ridge fault. This ~1 Ma map has been digitized and restored.

The ~6 km wavelength folding of the Mid Channel (Blue Bottle) trend beneath Santa Barbara Channel provides a clear example to compare models. The western part of this structure is a N-verging fold. The backlimb is the same width, 4 km, for strata of different age, but the dip increases with increasing age for the post-160,000 year reflections dated at ODP site 893. It does not make any sense here for the slip to be greater than or equal to the backlimb width, as is required for syn-thrust strata by the fault-bend fold and fault-propagation fold models (Suppe, 1983; Suppe and Medwedeff, 1990). If this were true, slip since deposition of a 110,000 (+/- 10%) horizon would be 36 mm/yr, and would be 80 mm/yr for a 50,000 year horizon. In contrast, a listric thrust model predicts that slip is proportional to limb dip, and that the observed fold can be created with 1 or 2 orders of magnitude slower slip (Seeber and Sorlien, 2000).

The Mid Channel trend fold has increased in amplitude at 2 mm/yr since 200 Ka over part of its length, the same rate as the vertical motions due to fault slip and folding since 1 Ma. Huftile and Yeats (1995) proposed that since ~0.5 Ma, slip on the deep offshore Oak Ridge fault has been transferred to folds along the northern margin of Ventura basin at rates of 5 mm/yr. Our results indicate no change in the last 1 m.y. of rates of vertical motions due to slip on the offshore Oak Ridge fault and due to related folding, although there may be a change in the partitioning of this motion between faulting and folding. Shortening across the offshore Oak Ridge fault and its hanging-wall folds (Mid Channel trend) is only a few hundred meters in the last 1 m.y. Blind slip transferred to folds along the north margin of offshore Ventura basin will be evaluated using map restoration and by modeling the shape of the offshore folds against different possible fault geometries.

Shortening and vertical motion across the onshore E-W Oak Ridge fault are related to left-lateral motion on the ENE-WSW coastal section, which is again transformed into shortening and vertical motions on the ESE-WNW segment south of Santa Barbara. Onshore, near Santa Paula, the map restoration documents space problems that require the post-1 Ma left-lateral component across the Oak Ridge fault to be less than half the 3.5 km proposed by Yeats and Taylor (1989), or else that left-lateral shear is transferred across the footwall (north) block. NE-striking cross faults are suggested by the sharp bends in both the fault near Santa Paula and offshore, and by a sharp bend in a regional N-dipping fold limb between Oxnard shelf and Santa Cruz Island.