Fig. 4

Percentage of GHG emissions from various causes. (a) Gathering pipelines. (b) Transmission pipelines. The proportions are calculated based on the average values obtained from Monte Carlo simulations. The category “Others” mainly includes the following ten specific reasons: (1) destruction caused by boats, barges, drilling rigs, or other maritime equipment or vessels that are set adrift or have lost their mooring; (2) damage caused by cars, trucks, or other motorized vehicles or equipment not involved in excavation; (3) electrical arcing originating from other equipment or facilities; (4) intentional acts of damage; (5) accidents categorized as miscellaneous; (6) occurrence of nearby industrial, man-made, or other fire/explosion as the primary cause of the accident; (7) damage resulting from other external forces; (8) pre-existing mechanical damage unrelated to excavation; (9) accidents arising from routine or normal fishing or other maritime activities not related to excavation; (10) occurrences with unknown causes.