Revisiting the 1959 Hebgen Lake earthquake using optical image
correlation; new constraints on near-field 3D ground displacement
Abstract
Surface displacement data from earthquakes are essential for
characterizing the fault slip distribution with depth. The Hebgen Lake
earthquake was a large normal event with a geometrically complex surface
rupture, which broke across mountainous terrain. This study takes
advantage of high-resolution historical stereo-imagery to measure the
vertical and horizontal displacement from correlation of the
orthorectified pre- and post-earthquake image mosaics. The results
reveal new strike-slip surface ruptures which are possibly associated
with the aftershocks from 18\textsuperscript{th} August
1959. The kinematic role of these structures is likely related to the
accommodation of internal deformation induced by the mainshock strain
field. Additionally, the comparison of our results with the existing
displacement data shows that the OIC-derived offsets often exceed the
field measurements by $>$50\%. We
attribute this difference to the inelastic damage accommodated off the
main rupture.