Off-fault Deformation Associated with Strike-slip Faults

Habitable buildings can be protected from surface fault rupture by establishing structure “setback zones” similar in purpose to legally mandated zones in California and Utah. But post-earthquake surveys of offset and warped linear cultural features, believed to have been straight prior to the event, demonstrate that potentially damaging inelastic strains or off-fault deformation can extend tens of meters beyond the principal slip zone of strike-slip surface fault ruptures. Setback zones designed to also mitigate off-fault deformation are likely to be prohibitively wide, indicating the need for structural and geotechnical engineering solutions to accommodate the potentially damaging strains within adequate design buffers. This study analyzes nine strike-slip surface fault ruptures between 1906 and 2014 and develops a simplified procedure to quantify off-fault deformation based on earthquake magnitude and distance from the principal slip zone of strike-slip faults.