= Solution
\b[The rate of surface modification] controls how quickly a <fault scarp> is erased. Strong rainfall, runoff, slope failure and easily eroded <lithologies> can round or dissect a scarp; dry conditions and resistant rock often preserve it longer. <Alluvial fan> deposition and <aggradation> can bury a scarp even if erosion is slow. A young marker surface can preserve an offset that an older, strongly modified surface no longer records.
\b[The balance between <fault slip rate>, recurrence interval and marker age] controls whether renewed displacement outruns this modification. Rapid or repeated <normal faulting> can maintain a clear front, whereas a long interval after a small displacement permits smoothing. A very young fan deposited after the event may have no offset, while an older surface may retain cumulative rather than single-event <fault throw>. These two controls explain why absence of an obvious scarp is not proof of an inactive <fault>.
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