Time-Resolved Surface-Fault Displacement During the 2026 Kumamoto Earthquake From CCTV Video

Abstract: Video recordings can provide unusually direct constraints on the time evolution of coseismic surface-fault displacement, but quantitative analysis is complicated when camera motion and recording artifacts contaminate the apparent image motion. We analyze a secondary recording of CCTV footage that captured surface displacement during the 28 July 2026 Kumamoto earthquake. To our knowledge, this is only the second reported earthquake for which coseismic surface-fault motion has been captured directly by CCTV, following the 2025 Mw 7.7 Myanmar earthquake. Two independent approaches, pyramidal optical flow and normalized cross-correlation template matching, were applied to the available video frames, with common recording motion estimated from spatially separated reference regions. Image displacement was calibrated to the magnitude of the field-measured permanent offset vector (1.05 m right-lateral, 0.90 m east-side-up; 1.383 m total). The two methods yield closely consistent displacement histories. The central 20-80% of the permanent displacement developed over 0.87-0.91 s, corresponding to an average displacement rate of about 0.9-1.0 m/s. These estimates are stable across reasonable processing choices and target-region perturbations. Both methods also resolve a transient displacement maximum about 5-7% above the subsequent stable level, followed by reverse motion toward the final plateau. This apparent overshoot is robust in the video-derived displacement history, but a coherent residual artifact cannot be excluded because both analyses rely on the same secondary recording.