In seismic prone regions the seismic design of onshore (and offshore) pipelines is of paramount importance. One of the main earthquake-related geohazards that may induce excessive permanent ground displacements to a gas pipeline is active seismic faults that can lead to severe rock and soil dislocations up to the ground surface. Therefore, in areas where the crossing of a pipeline with an active seismic fault is unavoidable, extra care (i.e., a specialized study) is required to minimize its potential impact on the pipeline.

Nevertheless, in certain occasions the pipeline can be parallel or sub-parallel to the examined fault. In this case, there is a wrong impression in practice engineers that there is no risk for the pipeline. However, a potential rupture of the (main) fault will cause the application of almost uniform vertical and horizontal permanent ground displacements to the pipeline along the total length of the fault. Moreover, depending on the geological conditions of the fault hanging wall, the pipeline is expected to be substantially distressed mainly at the two edges of the fault. This distress is a result of the (generally smaller) secondary ruptures that will be developed (due to the three-dimensional geometry of the coupled problem of the pipeline and the surrounding soil) at the ground surface, generally normal to the primary fault rupture.

The current paper is focusing on this complex phenomenon of geotechnical earthquake engineering and soil-structure interaction, which should not be neglected as it can lead to insufficient design and pipeline failures. For this purpose, numerical analyses have been performed, based on elaborate finite element models that have been validated with experimental data. A detailed parametric study demonstrates the impact of various parameters and highlights the need for a holistic approach of designing against fault rupture that considers all aspects of this critical geohazard.