Vertical Coseismic Offsets Derived From High‐Resolution Stereogrammetric DSM Differencing: The 2013 Baluchistan, Pakistan Earthquake

The recent proliferation of high‐resolution (<3‐m spatial resolution) digital topography data sets opens a spectrum of geodetic applications in differential topography, including the quantification of coseismic vertical displacement fields. Most investigations of coseismic vertical displacements to date rely, in part, on preevent or postevent lidar surveys that are intractable or nonexistent in many locales. Stereogrammetric digital surface models (DSMs) derived from high‐resolution satellite optical imagery provide a new avenue for the retrieval of spatially dense vertical coseismic displacements on a global scale. In this study, we generated 2‐m resolution preseismic and postseismic DSMs from satellite optical imagery spanning the 2013 Mw7.7 Baluchistan strike‐slip earthquake that occurred on the Hoshab fault in southern Pakistan. We applied the Iterative Closest Point algorithm to the DSMs to quantify the coseismic vertical displacement field at a spatial resolution of 10–30 m and to generate 3‐D coseismic strain tensors. We found that across‐fault vertical offsets alternated between uplift and subsidence and varied between ~1 and 3 m in a nonsystematic manner along the Hoshab fault. We show that the preexisting topography and near‐fault geomorphology are variably consistent and inconsistent with the displacement kinematics of the 2013 earthquake, and we argue that these relationships highlight varied slip sense history along the Hoshab fault. Notably, topography along the southern extents of the Hoshab fault requires different surface displacement kinematics than occurred in the 2013 earthquake, suggesting that the Hoshab fault accommodates varying senses of slip (bimodal slip) through time.