For instance, remarkable structural damage has been identified after the 1971 San Fernando [10], 1999 Kocaeli, Turkey, and Chi-Chi, Taiwan [11], as well as the 2008 Wenchuan, 2009 Italy, and 2010 Chile earthquakes [12; 13]. The recent 2023 M\({}_{\rm w}\) 7.8 earthquake in Turkey caused significant damage to the Kahramanmaras-Gaziantep natural gas transmission pipeline, leading to the occurrence of heavy explosions and extensive disruption of gas supplies in the cities of Gaziantep and Hatay [14]. In addition, it is worth noting that the impact of earthquake-related geohazards on CI extends beyond direct damage, with substantial indirect losses affecting industries worldwide. Indicatively, a significant part of the Trans-Ecuadorian Pipeline, approximately equal to 70 km, was seriously damaged by the 1987 Ecuador earthquake. As a consequence, 60% of Ecuador's export revenue was lost, and combined with the 5 months of reconstruction, the economic losses reached 800$ million [15]. Considering the fact that the complete avoidance of seismically geohazardous areas is not always feasible due to various techno-economic constraints (e.g., uneven topography) and geopolitical conflicts, it is evident that earthquake-related geohazards constitute critical factors during the process of optimal route selection. Nevertheless, to the best of the authors' knowledge, very few relevant publications can be found in the literature that fully take into account the presence of earthquake-related geohazards during the route selection of CI. In most cases, earthquake-related geohazards are either based on simplifications (i.e., named as soil and geology factors, geological and natural hazards, etc.) and rules of thumb (i.e., \"vertically crossed obstacles\") without performing a more elaborate analysis, treated as absolute barriers (i.e., that cannot be crossed), or completely ignored [8; 9; 16; 17; 18]. Consequently, further research is required for the optimal route selection of CI in areas characterized by the presence of earthquake-related geohazards. Recently, the authors facilitated the process of optimal route selection of large-scale lifelines, such as offshore natural gas pipelines, fiber-optic and power transmission cables, subjected to the earthquake-related geohazards of active seismic faulting and slope instability. The advanced capabilities and functionality of GIS for geospatial processing, as well as the provided LCPA technique for optimal routing, have been successfully combined with MCDMs through the Python computer programming language. By allocating varying weight values to the design criteria, different scenarios were generated to accurately evaluate their effects on the CI and effectively analyze all possible CI routing options in seismic-prone areas [19; 20; 21]. This article is a revised and expanded version of a paper entitled: \"GIS-based multi-criteria decision methodology for the optimal routing of large-scale lifelines against earthquake-related geohazards\", which was presented at the PTC-2024 Conference held in Berlin, 8-11 April 2024 [22]. The current paper presents an upgraded version of the aforementioned computational tool that aims to assist engineers in achieving the optimal route of onshore high-pressure gas pipelines, taking into account a wide range of design criteria. Emphasis is given to the presence of the aforementioned earthquake-related geohazards, including the geohazard of soil liquefaction, which has not been incorporated in previous versions. The main novelty of the present work regarding earthquake-related geohazards is that the proposed decision-support tool has also examined a more complex geohazard, i.e., the combined rupture of the main and secondary seismic faults being non-parallel or even perpendicular to the main fault. In general, this complex phenomenon has not been addressed in the process of CI optimal routing, and as it will be explained in the sequence, it can be crucial for pipelines.