Abstract

The Stockton and Vernalis Faults are major structural features in the southern Sacramento Basin of California. Both faults are reverse faults with some component of left lateral strike slip. Most of the major gas accumulations in the area are associated with the Stockton and Vernalis Faults (Figure 1). The Stockton Fault has a north-south orientation at the intersection point with the Vernalis Fault, which changes from a northwesterly trend at the Tracy anticline to a westerly trend at the intersection point. Throw along the faults are varies with depth but is relatively consistent except at the intersection point of the two faults, which occurs in the vicinity of section 18, T2S R5E, San Joaquin County, California. The fault planes appear to join an become one fault plane with increased throw as evidenced by the fault cut in the Atlantic Holly Sugar #1 well in section 18, T2S R5E. The combined fault plane, labeled the Stockton-Vernalis (SV) fault, then is cut by yet another northwesterly trending thrust fault located west of the SV intersection named for this paper the West Tracy Fault. This intersection could hold some significance in future exploration in the area. Other thrust faults in Sacramento Basin have been found to be important to trapping gas and an understanding of these faults will yield further exploration targets.