International audienceA holistic view of the Bengal–Nicobar Fan system requires sampling the full sedimentary section of the Nicobar Fan, which was achieved for the first time by International Ocean Discovery Program (IODP) Expedition 362 west of North Sumatra. We identified a distinct rise in sediment accumulation rate (SAR) beginning ∼9.5 Ma and reaching 250–350 m/Myr in the 9.5–2 Ma interval, which equal or far exceed rates on the Bengal Fan at similar latitudes. This marked rise in SAR and a constant Himalayan-derived provenance necessitates a major restructuring of sediment routing in the Bengal–Nicobar submarine fan. This coincides with the inversion of the Eastern Himalayan Shillong Plateau and encroachment of the west-propagating Indo–Burmese wedge, which reduced continental accommodation space and increased sediment supply directly to the fan. Our results challenge a commonly held view that changes in sediment flux seen in the Bengal–Nicobar submarine fan were caused by discrete tectonic or climatic events acting on the Himalayan–Tibetan Plateau. Instead, an interplay of tectonic and climatic processes caused the fan system to develop by punctuated changes rather than gradual progradation

International audienceTrying to understand where major earthquakes and tsunamis might occur requires analysis of the sediments pouring into a subduction zone. Thick sediments were expected to limit earthquake and tsunami size in the Sumatran megathrust event in 2004, but the magnitude 9.2 earthquake defied expectations. Hüpers et al. analyzed sediments recovered from the Sumatran megathrust. They found evidence of sediment dehydration, which increased fault strength and allowed for the much larger earthquake to occur. Thus, models of other subduction zones, such as the Gulf of Alaska, may underestimate the maximum earthquake magnitude and tsunami risk

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S U M M A R YOscillatory hydraulic tests were conducted on samples of two varieties of Fontainebleau sandstone differing in porosity and a stacked sample of the two varieties. Simultaneous measurements of the upstream and downstream pressures and the upstream fluid flow permit the calculation of permeability and specific storage by two methods, the conventional upstreamdownstream pressure analysis and the upstream pressure-flow analysis. The pressure analysis yields a relatively constant permeability for the high-porosity sample at different effective pressures and oscillation periods, but slightly period-dependent permeability for the low-porosity samples and the stacked sample. The period dependence diminishes with increasing period. Estimates of specific storage capacity derived from pressure analysis appear problematic. For samples with the higher porosity, values are highly uncertain due to peculiarities of the solution space used to convert attenuation and phase shift to permeability and storage capacity. For the sample with the lower porosity and the stacked sample, normalized storage capacity values fall significantly below the physical limit constituted by sample porosity. The flow analysis yields well-constrained values of permeability and specific storage capacity for the sample with the higher porosity. For the samples with the lower porosity and the stacked sample, both parameters show a strong dependence on oscillation period. We suppose that the two methods probe different portions of the pore space and thus yield different results for heterogeneous samples when periods fall below a critical period estimated from the scaling relation for hydraulic diffusivity. Flow analysis probes the portion of the sample facing the upstream reservoir with a thickness approximated by the penetration depth. In contrast, the pressure analysis probes the dominant flow path connecting the sample ends. In samples with connected but stagnant pores, the storage capacity has two distinct contributions from an effectively storing porosity and an effectively conducting porosity. The observed period dependence of storage capacity probably reflects the shift in balance between the two contributors.

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1401.5 mbsf (Hole C0002A; Expedition 314 Scientists, 2009a) and 0 to 980 mbsf (Hole C0002G; Expedition 332 Scientists, 2011). Coring at Site C0002 previously sampled 0-203.5 mbsf (Holes C0002C and C0002D) and 475-1057 mbsf (Hole C0002B) (Expedition 315 Scientists, 2009b). During riser operations, we expanded the data sets at Site C0002. Gas from drilling mud was analyzed in near real time in a mud-gas monitoring laboratory and was sampled for postcruise research. Continuous LWD/MWD data were collected in real time for quality control and for initial assessment of borehole environment and formation properties. Recorded-mode LWD data provided higher spatial sampling of downhole parameters and conditions. Cuttings were sampled for standard shipboard analyses and shore-based research. Riserless Methods 1

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[1] We performed mechanical tests on mudstone samples cored in the hanging wall of a major out of sequence thrust fault in the Nankai accretionary complex prism, SW Japan, (1) to understand the consolidation and shear behaviors of slope sediments that form the fault zone and wall rock of this important structural feature in the upper several kilometers, and (2) to constrain in situ stresses and pore pressure, two fundamental parameters governing deformation processes in subduction zones, which are notoriously difficult to measure. We conducted deformation experiments on a suite of samples taken from depths of 20-150 mbsf, including six uniaxial consolidation tests and one isotropic consolidation test. For three of these tests, we conducted undrained triaxial compression testing following consolidation. Our results suggest that in situ pore pressure is hydrostatic and that during sedimentation and burial, the effective horizontal stress is ∼41% of the effective vertical stress. In combination with analysis of wellbore failures documented during drilling of the borehole, our experimental data allow us to define the complete stress tensor, including the magnitude of in situ minimum and maximum horizontal stresses, in the hanging wall of this major fault zone. The maximum horizontal stress magnitude is comparable to that expected for sedimentation and uniaxial burial, whereas the minimum horizontal stress lies below this value. This suggests (1) that the shallow sedimentary section was subjected to extension subparallel to the trench during or following burial and (2) that stresses associated with plate convergence are not effectively transmitted within these shallow sediments.