Formation and Evolution of Submarine Mud Volcanoes and Fluid Seepage Patterns: A Comparative Study in Different Tectonic Settings

Abstract

As products of deep fluid-tectonic-sedimentary coupling, mud volcanoes have scientific value for oil–gas exploration, indicate neotectonic activity and aid global climate change studies. This study focuses on mud volcanoes in China's offshore areas (northern South China Sea, Okinawa Trough of the East China Sea), investigating tectonic control on their development and fluid activity's impact on shallow gas and gas hydrate accumulation. Through numerical simulation, stress field analysis and comparative geological background analysis, key findings include: (1) Tectonically controlled distribution: strike-slip extensional basins host large mud diapirs, extensional basins small–medium ones and compressional back-arc basins show zonal clustering; intensified tectonic activity exacerbates fluid seepage. (2) Formation relies on coupling of ‘material basis-dynamic conditions-triggering mechanisms’: Early Cenozoic mud-rich strata (material), overpressure (driven by undercompaction/hydrocarbon generation, dynamics), and tectonic/seismic activity (triggers). (3) Fluid seepage correlates with parameters: overpressure coefficient positively correlates with eruption intensity; shallower source layers and increased compressive stress enhance seepage efficiency. (4) Mud volcanoes influence accumulation via ‘gas supply-channel transport-temperature-pressure regulation’, acting as a ‘source-channel-trap’ system to promote enrichment, though deep thermal fluid upwelling may cause hydrate dissociation and hazards. This study elucidates their formation mechanisms and resource-environmental effects, providing theoretical support for deep-water oil–gas exploration and geohazard early warning.