Abstract
<title>Abstract</title> <p>Landslides reoccur in the middle of the Cameroon Volcanic Line, which carries no equipment able to monitor sluggish ground motion before collapse. On 19 September 2025, a landslide in Njintout, Foumban district, destroyed about one hundred homes. Two smaller failures had preceded it, none of which triggered a reaction. This research leverages openly accessible Sentinel-1 data to identify such movements. Thirty-six Sentinel-1A observations on ascending orbit 59 (30 June 2024 to 23 October 2025) were processed using the Small Baseline Subset technique across 145 pairs, with adaptive Goldstein filtering, phase unwrapping at a coherence threshold of γ ≥ 0.080 calibrated locally, and coherence-weighted inversion. At the failure site a positive line-of-sight velocity of + 5.85 mm yr⁻¹ (95% confidence range + 2.70 to + 8.99) was recovered. Two segments characterize the record better than one. A change-point analysis sets the commencement of sustained motion at 8 May 2025, four and a half months before failure, at + 21.8 mm yr⁻¹ (+ 12.0 to + 31.7) versus a pre-onset rate indistinguishable from zero. The record separates from a stable cell 2 km distant by six times the local dispersion and surpasses a noise-only null in less than 1 in 5,000 resamples. Applying the same method throughout the larger extent matches 17.7% of valid cells; however, inside the failure neighborhood, it indicates one contiguous zone rather than the failure cell. The signature localizes slopes of concern, not failure locations. With no ground measurements available, this study is a detection near the sensitivity limit rather than a verified measurement.</p>