Which pairing is used for strike direction in the United States?

• A. NW or SE
• B. NE or SE
• C. SW or NW
• D. NE or NW

Answer: (D)

Strike direction describes the orientation of a line lying in the plane, measured from north. In United States practice, this direction is given using quadrant bearings, specifically toward the northeast or northwest. That means a bedding plane that trends roughly northeast–southwest is labeled with a strike toward the northeast (the opposite direction would be southwest, but we typically state the forward NE direction). Likewise, a line trending northwest–southeast is labeled with a strike toward the northwest (the opposite direction would be southeast). Because those two quadrants cover the common strike orientations seen on US maps, the standard labeling uses NE or NW. The other directions would represent the opposite directions along the same line or would describe a dip-related orientation, which is not how the strike is named.