Code of Federal Regulations Title 43. Public Lands:  Interior § 43.3150.0–5 Definitions

(a) Oil and gas geophysical exploration means activity relating to the search for evidence of oil and gas which requires the physical presence upon the lands and which may result in damage to the lands or the resources located thereon. It includes, but is not limited to, geophysical operations, construction of roads and trails and cross-country transit of vehicles over such lands. It does not include core drilling for subsurface geologic information or drilling for oil and gas;  these activities shall be authorized only by the issuance of an oil and gas lease and the approval of an Application for a Permit to Drill. The regulations in this part, however, are not intended to prevent drilling operations necessary for placing explosive charges, where permissible, for seismic exploration.

(b) Casual use means activities that involve practices which do not ordinarily lead to any appreciable disturbance or damage to lands, resources and improvements. For example, activities which do not involve use of heavy equipment or explosives and which do not involve vehicular movement except over established roads and trails are casual use.