= Solution
A <displaced drainage> forms when repeated horizontal <fault slip> offsets a channel and its upstream and downstream reaches no longer line up. In plan view, draw two initially continuous channel reaches crossing the <fault>, translate one side parallel to the <fault strike>, and connect the reaches by a short fault-parallel reach. A <linear valley> develops where erosion follows damaged rock along a straight <fault zone>.
In Attachment A, use the \b[oblique, relatively straight valley running southwest–northeast through the lower centre towards the upper right]. For an identifiable example, follow the central approximately north–south drainage to its bend near the southern edge of the central basin, about $(u,v)=(0.46,0.67)$, where $u$ is fraction from the left image edge and $v$ fraction from the top. Mark its deflected reach and the adjacent straight valley. The positional precision is at the level of the supplied image; establishing a numerical <fault offset> would require correlated piercing points and field checks.
\Image[/past-exam-of-the-year-2-of-the-earth-sciences-geology-course-of-the-university-of-oxford/2023/paper-1-tectonic-interpretations.png]
{title=Original interpretive sketches for Attachments A and B, with normalized image positions and a normal-fault relay}
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