A lack of any dislocation found on the images along the Opak River fault made evident the lack of movement along that fault, and though the aftershocks were occurring at a depth of , the deformation was distinct at the surface. The observed ground deformation that was detailed by the differential satellite images and Global Positioning System measurements was roughly east of (and parallel to) the Opak River Fault, along a zone that passed through the USGS' epicenter, and delineated a NE trending vertical fault (a dip of 89°). The displacements were not more than and indicated left-lateral strike-slip motion as well as a component of reverse slip, and to the west of the Opak River Fault (and closer to the areas of damage) strong ground motion triggered subsidence of volcanic deposits from Mount Merapi.