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The base of the gas hydrate stability zone (GHSZ) is a critical interface, providing a first-order estimate of gas hydrate distribution. Sensitivity to thermobaric conditions makes its prediction challenging particularly in the regions with dynamic pressure-temperature regime. In Green Canyon in the northern Gulf of Mexico (Block GC955), the seismically inferred base of the GHSZ is 450 meters (1476 ft) below the seafloor, which is 400 m (1312 ft) shallower than predicted by gas hydrate stability modeling using standard temperature and pressure gradient assumptions, and an assumption of structure I (99.9% methane gas) gas hydrate. We use 3D

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We use a large strain geomechanical model and critical state soil mechanics to study the evolution of stress and deformation in an evolving fold-and-thrust belt and its underlying footwall sediments. Both mean effective stress and deviatoric stress contribute to porosity loss within the wedge with 35% of the porosity loss resulting from increased shear. As a result, porosity increases abruptly across the décollement because both mean-effective and shear stresses are much higher inside the wedge than in the footwall. As the basal friction coefficient (μ b ) increases, more shear stress is transmitted across the décollement, resulting in additional compaction of the footwall sediment and decrease in the porosity contrast across the décollement. As the internal friction coefficient (μ s ) increases, the wedge sediment is more compacted because it can withstand higher mean-effective and deviatoric stresses. Inside the wedge, the sediment experiences subhorizontal shortening strain and subvertical elongation strain. We predict a 10-30 km wide "transition zone" in which the shear-stress ratios and compaction curves change rapidly between compressional critical state failure and uniaxial strain (K 0 ) state. Our model results agree with the taper angles and the stress orientations predicted by critical taper theory. This large-strain drained modeling approach provides first-order insights into the mechanical processes of loading and compaction in fold-and-thrust belts and a foundation for understanding field observations of pressure, stress, and deformation in thrust belt systems.While critical taper theory provides insight into the relations among pore pressure, material strength, and wedge geometry, it does not address the mechanics of sediment deformation within and beneath the wedge. Sediments in the wedge experience great horizontal shortening and vertical thickening caused by lateral tectonic loading. As a result, systematic changes in porosity occur within and below wedges. For GAO ET AL. 4454