Distributed Lower‐Crustal Flow Beneath the Central Xianshuihe–Xiaojiang Fault System: Reconciling Geodesy and Geology

Abstract We use recently compiled GNSS velocities across the Zemuhe‐Daliangshan fault zone, part of the central Xianshuihe‐Xiaojiang fault system, to reconcile a long‐standing mismatch between geodetic and geologic slip‐rate estimates. We show that conventional elastic dislocation models yield slip rates and locking depths that conflict with seismic and geologic constraints. In contrast, models incorporating a viscoelastic rheology for the lower crust yield geologically consistent slip rates, with the Zemuhe fault slipping 7 mm/yr and the Daliangshan fault slipping 2 mm/yr, and locking depths more consistent with microseismicity (17–20 km). In contrast with major strike‐slip faults worldwide, deformation in this immature system appears distributed over a broad lower‐crustal region. These findings indicate that interpreting interseismic deformation with purely elastic models in fault zones that lack a mature, localized shear zone at depth can lead to misleading results.