Map showing inferred and mapped basement faults, San Juan Basin and vicinity, New Mexico and Colorado

Interpretation of more than 1,100 mi (1,750 km) of seismic reflection data in the San Juan Basin and vicinity allowed us to map a large number of faults that have measurable offset at the top of the Proterozoic crystalline basement. Predominant fault trends are N. 60o–70o W. and N. 30o–40o E. with a typical spacing of 4–10 mi (6–16 km). The orthogonal pattern was established in the Precambrian, but episodic movements in the late Paleozoic, Mesozoic, and Cenozoic have been measured by the authors on a number of the faults. Periods of significant movement correspond to recognized orogenic events, particularly the Pennsylvanian to Permian Ancestral Rocky Mountain orogeny and the early Tertiary Laramide orogeny. The seismic data set available to the authors is composed of long regional lines and shorter lines used for oil and gas prospect evaluation. All lines of the data were shot conventionally as two-dimensional surveys between 1969 and 1983, most utilizing dynamite as the source. Data were purchased from Bass Enterprises Production Co., Dome Petroleum Co., El Paso Natural Gas Co., Northwest Exploration Co., and Tenneco Oil Co. and were borrowed from Amoco Production Co., Maxus Exploration Co., Meridian Oil Co., and the Ute Mountain Ute Tribe (Wintershall Oil Co.). In addition, two small seismic surveys were shot by the U.S. Geological Survey over uranium deposits in the southwestern part of the study area. With the exception of the USGS data, all lines and shot points are proprietary.