Partitioned off‐fault deformation in the 2016 Norcia earthquake captured by differential terrestrial laser scanning

Field measurements of co‐seismic fault slip often differ from surface slip models derived from satellite geodesy. Quantifying these differences is challenging as many geodetic techniques inadequately image near‐fault deformation. We use an iterative closest point (ICP) algorithm to difference pre‐ and post‐earthquake terrestrial laser scanning (TLS) point clouds to reveal cm‐scale patterns of surface deformation caused by shallow fault slip in the 2016 Mw 6.6 Norcia (central Italy) earthquake. TLS offsets are constant along the fault and match average field measurements. 84% of vertical displacement occurs on a discrete fault zone, with 16% of deformation distributed across a narrow zone <4 m wide. In contrast, horizontal deformation is distributed over an 8 m wide zone with c. 50% of extension accommodated as off‐fault deformation (OFD). The cm‐scale observation of deformation shows that horizontal and vertical co‐seismic OFD is partitioned – in this case, OFD is dominated by horizontal deformation.