21,248 research outputs found
RRS James Clark Ross Cruise 253, 26 Jul -25 Aug 2011. Arctic methane hydrates
No full textThe cruise built on the successful geophysical and geochemical mapping, undertaken during the 2008 IPY voyage JCR211 (Westbrook et al., 2009) that made the first comprehensive survey of methane bubble plume venting along the western Svalbard margin. The main achievements of JCR253 included the recovery of the ESONET demonstration mission AOEM - MASOX seafloor lander (with recovery of 10 months of physical and biogeochemical parameters from a vigorous bubble plume site) and its deployment for a further 12 months at the same site (for recovery in August 2012), completion of 23 HyBIS ROV dives, totaling 35 hr. Seafloor video and photographs, were completed along transects in both 420 – 380 m and 80-90 m water-depths, but additionally HyBIS was used to sample bubble plume fluids at seafloor “vents” for geochemical analysis, and bubble imaging to measure bubble sizes and ascent rates. A suite of 14 piston / gravity cores were acquired along three transects perpendicular to both the interpreted position of the hydrate stability zone outcropping at the seafloor and general linear band of bubble plumes emitting from the seafloor around ~ 390 m. A comprehensive suite of 28 CTD stations were completed for physical / chemical sensing and water-sampling along the three transects (co-located with sediment and box cores) and the shallow-water sites. Additionally, the active acoustic bubble BOB imaging system was deployed to record active methane bubble release at a representative bubble stream at 390 m for an 18-day deployment. A major “discovery” of the cruise is the observation of active methane bubble release in shallow- ater (80-90 m water-depth) landward of the previously described edge of the hydrate stability zone outcropping near the seafloor at water-depths of 420 – 380 m
Applying the Coulomb Failure Function with an optimally oriented plane to the 2008 Mw 7.9 Wenchuan earthquake triggering
No full textThe Coulomb failure function (CFF) quantitatively describes static stress changes in secondary faults near the source fault of an earthquake. CFF can be employed to monitor how static stress transfers and then shed some light on the probability of successive events occurring around a source fault. In this paper we focus on the CFF and particularly on optimally oriented planes. We present a unified model to determine an optimally oriented plane and its corresponding Coulomb stress, then apply the model to the 2003 Mw 6.6 Bam (Iran) earthquake and the 2008 Mw 7.9 Wenchuan (China) earthquake, thereby checking its effectiveness. Our results show that spatial correlation between positive Coulomb stress changes and aftershocks are, for the 2003 Bam earthquake, 47.06% when elastic Coulomb stress changes are resolved on uniform planes and 87.53% when these are resolved on optimally oriented planes at depth; for the 2008 Wenchuan earthquake the correlations are 45.68% and 58.20%, respectively. It is recommended that account be taken of optimally oriented planes when drawing a Coulomb stress map for analyzing earthquake triggering effects
Bulk and surface structures of the aurivillius phases: Bi4-xLaxTi3O12 (0 <= x <= 2.00)
No full textAppropriate communication formats between researchers
No full textWe were surprised to see yet another Letter-to-the-Editor from Arumugam and colleagues recently sent to this journal (Arumugam, 2016; Arumugam and Chandrasekaran, 2019; Arumugam et al., 2020). For their Letter in response to our review (Klerx et al., 2019), we believe direct communication to the corresponding author would have sufficed for most elements. The content of Letters-to-the-Editor can then be reserved for pertinent discussions of interest to the broad readership of the journal.No Full Tex
X-ray photoelectron spectroscopy and high resolution electron microscopy studies of Aurivillius
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Comparative feasibility study of a 30 MW disruptive floater solution with a 15 MW PivotBuoy and a benchmark 15 MW semi-submersible floater in the Bay of Biscay
No full textThis paper investigates the technical, life cycle, and economic feasibility of a 30 MW upscaled downwind turbine, comparing it to a 15 MW X1 Wind PivotBuoy downwind turbine and a benchmark 15 MW IEA Umaine VolturnUS-S upwind turbine in the 450 MW Sud de la Bretagne I wind farm site. The study is significant due to the rising energy demand, the potential for decreasing the levelized cost of energy with increased turbine size, and the optimized use of space. The size limit of current upwind turbine designs could be addressed using a downwind turbine solution.The research is conducted by modelling the global dynamic response of the structure using OpenFAST and computing the natural frequencies and stresses using a finite element model. A lifecycle analysis is performed to identify potential pitfalls and bottlenecks by analysing the individual lifecycle phases. The economic feasibility is assessed by simulating the annual energy production using TOPFARM and utilizing structural analysis and lifecycle assessment to quantify capital, operational, and abandonment expenditures. Based on the annual energy production and the performance indicators the levelized cost of energy is calculated.The findings indicate that while the global stability is within boundaries, the stress in members is too high with a simple scale-up of the proposed design. Bottlenecks are found in lifting operations and supply chain readiness. The levelized cost of energy and capital expenditure increased due to substructure self-weight, rendering the proposed 30 MW scale-up currently unfeasible when compared to the other two wind farms.These findings are important as they demonstrate that the 15 MW X1 Wind PivotBuoy is not scalable without design changes. The levelized cost of energy does not decrease with an increased floater solution. The 15 MW X1 Wind PivotBuoy downwind turbine seems more economically viable, making it a more interesting option for future development.Civil Engineerin
The 2010 MW 6.8 Yushu (Qinghai, China) earthquake: constraints provided by InSAR and body wave seismology
No full textBy combining observations from satellite radar, body wave seismology and optical imagery, we have determined the fault segmentation and sequence of ruptures for the 2010 Mw 6.8 Yushu (China) earthquake. We have mapped the fault trace using displacements from SAR image matching, interferometric phase and coherence, and 2.5 m SPOT-5 satellite images. Modeling the event as an elastic dislocation with three segments fitted to the fault trace suggests that the southeast and northwest segments are near vertical, with the central segment dipping 70° to the southwest; slip occurs mainly in the upper 10 km, with a maximum slip of 1.5 m at a depth of 4 km on the southeastern segment. The maximum slip in the top 1 km (i.e., near surface) is up to 1.2 m, and inferred locations of significant surface rupture are consistent with displacements from SAR image matching and field observations. The radar interferograms show rupture over a distance of almost 80 km, much larger than initial seismological and field estimates of the length of the fault. Part of this difference can be attributed to slip on the northwestern segment of the fault being due to an Mw 6.1 aftershock two hours after the main event. The remaining difference can be explained by a non-uniform slip distribution with much of the moment release occurring at depths of less than 10 km. The rupture on the central and southeastern segments of the fault in the main shock propagated at a speed of 2.5 km/s southeastward toward the town of Yushu located at the end of this segment, accounting for the considerable building damage. Strain accumulation since the last earthquake on the fault segment beyond Yushu is equivalent to an Mw 6.5 earthquake
Earthquake source parameters of the 2009 Mw 7.8 Fiordland (New Zealand) earthquake from L-band InSAR observations
No full textThe 2009 MW7.8 Fiordland (New Zealand) earthquake is the largest to have occurred in New Zealand since the 1931 Mw 7.8 Hawke’s Bay earthquake, 1 000 km to the northwest. In this paper two tracks of ALOS PALSAR interferograms (one ascending and one descending) are used to determine fault geometry and slip distribution of this large earthquake. Modeling the event as dislocation in an elastic half-space suggests that the earthquake resulted from slip on a SSW-NNE orientated thrust fault that is associated with the subduction between the Pacific and Australian Plates, with oblique displacement of up to 6.3 m. This finding is consistent with the preliminary studies undertaken by the USGS using seismic data
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