Quantifying fault interpretation uncertainties and their impact on fault seal and seismic hazard analysis

Abstract

Fault-horizon cut-off data extracted from seismic reflection datasets are used to study the geometry, displacement distribution, and growth history of normal faults. Our study assesses the influence of three fault interpretation factors (repeatability, measurement obliquity, and cut-off type) on derived fault properties. We investigate uncertainties in throw, heave, displacement, and dip, extracted from continuous and discontinuous cut-offs along multiple horizons across four sub-linear faults in the Chandon-3D seismic cube, located offshore NW Australia. Mean differences between repeated interpretations are ~±10% for throw and 13-23% for heave, with greater uncertainties observed locally (e.g., in areas of structural complexity). Measurement obliquity, where cut-offs are interpreted along non-perpendicular transects to fault strike, introduces uncertainty depending on the degree of obliquity (particularly when 20˚), horizon, fault, and the fault property being measured. Obliquity related uncertainties were found to not decrease the repeatability of the derived fault parameters, with the seismic image data found to have a greater influence. For both the aforementioned interpretation factors, continuous cut-offs generally exhibit greater uncertainties compared to discontinuous cut-offs. Our findings indicate that obliquity and repeatability have a limited impact on fault transmissivity calculations but may significantly affect fault-based seismic hazard assessment.