About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 67 (1983)

Issue: 3. (March)

First Page: 461

Last Page: 461

Title: North Channel Slope Previous HitFaultNext Hit, Santa Barbara Basin, California: A Reevaluation: ABSTRACT

Author(s): P. J. Fischer, G. W. Simila

Article Type: Meeting abstract


Recently a "major Previous HitfaultNext Hit zone," the "North Channel Slope Previous HitfaultNext Hit" was mapped along the northern margin of the Santa Barbara basin by U.S. Geological Survey personnel. The Previous HitfaultNext Hit consists of a steep topographic escarpment (the north channel slope) and two well-documented faults to the east and west. By connecting the Pitas Point Previous HitfaultNext Hit, the escarpment, and the F-1 (or Point Conception) Previous HitfaultNext Hit to the west, a major zone over 100 km (62 mi) in length was postulated. Unfortunately, the connection and the continuous zone are nonexistent.

We have reviewed over 100 deep penetration to high resolution seismic reflection profiles along the escarpment between the Point Conception Previous HitfaultNext Hit and Coal Oil Point--a distance of 50 km (31 mi). No through-going Previous HitfaultNext Hit zone is present. Several small, discontinuous faults are mapped, such as the faulting south of the Molino anticlinal fold. But continuous, unbroken, late Neogene and Quaternary reflectors separate such minor high-angle reverse faults. Our interpretation of the deep structure along the margin is in agreement with that of the industry; there is no through-going Previous HitfaultNext Hit zone.

Rather than connecting with the "steep escarpment," the Pitas Point Previous HitfaultNext Hit appears to die out south of the Hondo anticlinal structure and cannot be traced beneath the Conception submarine fan to the west. In this area, the Previous HitfaultNext Hit is expressed as a series of steeply south-dipping, monoclinal flexures.

The F-1 or Point Conception Previous HitfaultNext Hit dies out immediately west of Gaviota. From this point westward to Point Conception, it is a north-dipping (65°±), high-angle reverse system that is composed of three en echelon segments with total length of approximately 20 km (12.5 mi) but less than 25 km (15.5 mi). Holocene activity along the eastern and western Previous HitfaultNext Hit segments is documented by the disruption of the Holocene shelf surface and the distribution of Holocene sediment veneer. The surface over the Previous HitfaultNext Hit zone is bowed about 3 m (10 ft), and the estimated maximum rate of uplift is 0.3 mm/yr.

The South Santa Ynez Previous HitfaultNext Hit extends offshore southwestward from Gaviota. The Previous HitfaultNext Hit is cut by the Point Conception Previous HitfaultNext Hit near the shelf break. Beyond the edge of the shelf, the South Santa Ynez Previous HitfaultNext Hit is located south of the Point Conception Previous HitfaultNext Hit, and represents a north-dipping, high(?)-angle reverse Previous HitfaultNext Hit. The latest displacements appear to be mid-late(?) Quaternary. The western part of the Previous HitfaultNext Hit, which underlies the Conception fan, is poorly defined.

A review of the earthquake activity (1932-1981) of the northwestern Santa Barbara Channel region shows several scattered epicenters with magnitude range of 3.0 to 4.5. The Previous HitfaultNext Hit plane solution for the October 1, 1959 (M = 4.5), event indicates right-lateral strike-slip faulting along a north-south direction with northeast-southwest compressive stress. No major historical earthquakes (1800-1932) have occurred in this region, nor is there a trend of epicenters along the north channel slope.

In summary, the existence of a "North Channel Slope Previous HitfaultTop zone" is not supported by the available evidence.

End_of_Article - Last_Page 461------------

Copyright 1997 American Association of Petroleum Geologists