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For regional coverage, use stereo photogrammetry from overlapping satellite or airborne imagery, or a radar-derived digital elevation model where suitable data exist. Match the same terrain features in images taken from different known viewing positions, infer their three-dimensional positions by triangulation, and georeference and grid the result. Satellite stereo or interferometric radar can cover $10^4\mathrm{k}{\mathrm{m}}^2$ efficiently; choose pixel size and vertical precision fine enough for the fault scarps of interest, rather than assuming every regional model resolves small scarps.

InSAR topographic mapping uses the phase difference from a known viewing baseline; repeat-pass deformation work must separate that height contribution from actual motion. Vegetation, cloud, radar shadow and steep slopes can leave gaps or represent the canopy rather than bare ground.^[ref] Ground control and independent elevation checks are needed before interpreting small relief as active faulting.

After removing orbital, topographic and atmospheric contributions, an earthquake InSAR radar interferogram would show elongated displacement lobes and generally closed or nested fringes associated with uplift and horizontal shortening of the hanging wall. Each full phase cycle represents ${\lambda }_r/2$ of line-of-sight displacement, where ${\lambda }_r$ is radar wavelength; equivalently $\Delta \varphi =\pm 4\pi d_{\mathrm{LOS}}/{\lambda }_r$, with sign fixed by processing convention.^[ref]

If primary slip reaches the surface, expect a displacement discontinuity across the surface trace: fringes can terminate or change abruptly there, and large near-fault gradients or disturbed ground may decorrelate. For a blind reverse fault, the elastic displacement field is continuous at the ground surface and spread over a broader zone, giving smoother gradients and fringes over the uplifted fold. A blind rupture can still create sharp local gradients or secondary faulting.

The exact colour order, number of fringes and sign of the displacement lobes cannot be fixed from this shaded relief alone. They depend on slip, depth and radar look direction; uplift is only one contribution to line-of-sight displacement.

Interferometric synthetic-aperture radar compares the phase of coherent radar returns acquired before and after the earthquake from closely repeated viewing geometry. After image registration and removal of orbital and topographic phase, the residual interferometric phase constrains relative ground displacement along the radar line of sight. Defining $u_{\mathrm{LOS}}$ positive toward the satellite and choosing the interferogram's phase order accordingly,One complete colour cycle therefore represents $\lambda /2$ of relative line-of-sight displacement. Reversing the image order reverses the displayed phase sign. This observes a projection of both horizontal and vertical motion, not uplift alone.^[ref]

If the main reverse rupture reaches the surface, coherent areas on opposite sides can show a displacement step: fringes become offset, truncated or abruptly juxtaposed along a trace. A narrow belt can lose interferometric coherence where cracking, intense gradients or changed scatterers prevent reliable phase comparison. If the rupture remains blind, a simple elastic model instead predicts a continuous surface displacement field, often a broad asymmetric lobe with continuous curved or closed fringes and a smooth displacement gradient across the projected tip.

These are diagnostic tendencies, not a unique test. An ordinary wrapped-phase boundary is just a $2\pi$ colour reset and is not itself a rupture. A step of an integer number of cycles can be hidden in wrapped phase; loss of interferometric coherence can hide either kind of near-field deformation. Vegetation, atmosphere and viewing direction also affect the pattern, and a displacement perpendicular to the radar line of sight is poorly sensed. Inspect coherence and unwrapped displacement, compare ascending and descending views where possible, and test a fault model against field observations. A sharp fold scarp above a blind rupture or a secondary shallow fault can also create localized gradients, so smooth fringes do not prove a buried tip and broken fringes alone do not prove a surface-breaking main rupture.

An image of the relative radar phase between co-registered coherent observations. A displacement changes the two-way path length, giving phase change proportional to $4\pi d_{\mathrm{LOS}}/{\lambda }_r$, with sign set by the adopted range convention. A full wrapped phase cycle therefore corresponds to half a radar wavelength of line-of-sight displacement. Orbital geometry, topography, atmospheric delay and scattering changes must be separated from deformation; a fringe is not uniquely an elevation contour or an earthquake displacement.^[ref]