What classification pertains to a fault that has a clearly detectable trace at or just below the ground surface?

The term that describes a fault with a clearly detectable trace at or just below the ground surface is "Well-Defined." This classification emphasizes the visibility of the fault trace, which can often be observed in the landscape and is an indication of the fault's presence and past activity. Recognizing a well-defined fault is crucial for assessing geological hazards, land use planning, and understanding the earth's tectonic history.

In geological terms, "active" refers to faults that have evidence of movement in recent geological time, usually within the last 10,000 years. "Seismic" relates more broadly to faults that can produce earthquakes rather than their physical appearance at the surface. "Subduction" is a specific type of tectonic boundary where one plate moves under another, leading to different geological features and behaviors, but it does not directly define fault visibility.

Therefore, the classification that best describes a fault detectable at or just beneath the ground surface is "Well-Defined."