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71.
A priori testing of sparse adaptive polynomial chaos expansions using an ocean general circulation model database 总被引:1,自引:0,他引:1
Justin Winokur Patrick Conrad Ihab Sraj Omar Knio Ashwanth Srinivasan W. Carlisle Thacker Youssef Marzouk Mohamed Iskandarani 《Computational Geosciences》2013,17(6):899-911
This work explores the implementation of an adaptive strategy to design sparse ensembles of oceanic simulations suitable for constructing polynomial chaos surrogates. We use a recently developed pseudo-spectral algorithm that is based on a direct application of the Smolyak sparse grid formula and that allows the use of arbitrary admissible sparse grids. The adaptive algorithm is tested using an existing simulation database of the oceanic response to Hurricane Ivan in the Gulf of Mexico. The a priori tests demonstrate that sparse and adaptive pseudo-spectral constructions lead to substantial savings over isotropic sparse sampling in the present setting. 相似文献
72.
A.K. Mundepi J.J. Galiana-Merino Kamal Conrad Lindholm 《Soil Dynamics and Earthquake Engineering》2010
Local site conditions substantially affect the characteristics of seismic waves and its potential to cause earthquake damage. To accurately identify the variation of seismic hazard at different locations within the cities, measurements from a three-component station may be used for estimating the resonance frequencies and evaluate the expected level of damage at each site. This information can also be complemented with array measurements of ambient noise in order to estimate the Vs profiles and characterize the corresponding sediment layers at each site. 相似文献
73.
Deterministic earthquake damage and loss assessment for the city of Bucharest, Romania 总被引:1,自引:0,他引:1
Dominik Lang Sergio Molina-Palacios Conrad Lindholm Stefan Balan 《Journal of Seismology》2012,16(1):67-88
On March 4, 1977, an earthquake with a moment magnitude M
w 7.4 at a hypocentral depth of 94 km hit the Vrancea region (Romania). In Bucharest alone, the earthquake caused severe damage
to 33,000 buildings while 1,424 people were killed. Under the umbrella of the SAFER project, the city of Bucharest, being
one of the larger European cities at risk, was chosen as a test bed for the estimation of damage and connected losses in case
of a future large magnitude earthquake in the Vrancea area. For the conduct of these purely deterministic damage and loss
computations, the open-source software SELENA is applied. In order to represent a large event in the Vrancea region, a set
of deterministic scenarios were defined by combining ranges of focal parameters, i.e., magnitude, focal depth, and epicentral
location. Ground motion values are computed by consideration of different ground motion prediction equations that are believed
to represent earthquake attenuation effects in the region. Variations in damage and loss estimates are investigated through
considering different sets of building vulnerability curves (provided by HAZUS-MH and various European authors) to characterize
the damaging behavior of prevalent building typologies in the city of Bucharest. 相似文献
74.
Conrad W. Curry Richard H. Bennett Matthew H. Hulbert Kenneth J. Curry Richard W. Faas 《Marine Georesources & Geotechnology》2013,31(4):231-252
Porosity is a fundamental property of marine sediment from which wet bulk density can be easily determined and used in a variety of geoacoustic, geotechnical, and sedimentological studies, analyses, and models. However, methods of sampling marine sands suffer from the common problem of core disturbance making the in situ porosity difficult to obtain. Embedding the sediment within an epoxy resin matrix will minimize the disturbance to the microfabric and preserve the in situ sedimentary structure for subsequent study. Image analysis can then be used on thin sections to study the microfabric and porometry. A comprehensive review and analysis of published data on the porosity of predominantly clean sands has been completed and a simple, accurate, and nondestructive technique is described for preparing and measuring the porosity of marine sediment (siliciclastic sand) that has been infiltrated aboard ship immediately upon sample collection and chemically fixed and infiltrated with epoxy shortly thereafter. The average porosity of 36 samples of marine sand collected offshore Fort Walton Beach, Florida, and embedded with resin was determined to be 41.30%. From the review of published data the average porosity of sand was determined to be 37.7%, 42.3%, and 46.3% for packed, natural (in situ), and loose packing conditions, respectively, for a range of sorting coefficients and grain sizes. 相似文献
75.
Hannah F. E. Jones Conrad A. Pilditch David P. Hamilton Karin R. Bryan 《新西兰海洋与淡水研究杂志》2013,47(3):370-392
Declines in bivalve populations have been quite common worldwide, often associated with coastal development, pollution and climate change. In addition to the impacts of these chronic stressors, occasional mass mortality events may have severe consequences on ecosystem services and biodiversity. In this study, we examined the impact of a mass mortality event of the clam (Austrovenus stutchburyi) on an estuarine food web and the grazing pressure exerted by the bivalve population. In February 2009, c. 60% of the clam population died in Whangateau Harbour, New Zealand. Population clearance rate calculations suggest that the clam population do not exert significant top-down control on phytoplankton biomass in the estuary, and thus the impact of the mortality event on bivalve grazing pressure was less severe than the reduction in abundance would suggest. A trophic model shows that phytoplankton play a limited role in the estuary food web, which is instead dominated by microphytobenthos and clams. This study highlights the importance of microphytobenthos in shallow estuaries, and the application of the trophic model is a useful tool that can identify key components of the ecosystem and could help inform monitoring programmes. 相似文献
76.
Conrad Childs Andrew Nicol John J. Walsh Juan Watterson 《Journal of Structural Geology》1996,18(12):1389-1397
The geometry and evolution of vertically segmented normal faults, with dip separations of < ca 11.5 m have been studied in a coastal outcrop of finely bedded Cretaceous chalk at Flamborough Head, U.K. Fault trace segments are separated by both contractional and extensional offsets which have step, overlap or bend geometries. The location of fault trace offsets is strongly controlled by lithology occurring at either thin (ca 1 mm-8 cm) and mechanically weak marl layers or partings between chalk units. Fault segmentation occurred during either fault nucleation within, or propagation through, the strongly anisotropic lithological sequence. An inverse relationship between fault displacement and number of offsets per length of fault trace reflects the progressive destruction of offsets during fault growth. The preservation of fault offsets is therefore dependent on offset width and fault displacement. Fault rock, comprising gouge and chalk breccia, may vary in thickness by 1.5–2.0 orders of magnitude on individual fault traces. Strongly heterogeneous fault rock distributions are most common on small faults (< 10 cm displacement) and are produced mainly by destruction of fault offsets. Shearing of fault rock with increasing displacement gives rise to a more homogeneous fault rock distribution on large faults at the outcrop scale. 相似文献
77.
Werner Conrad Karel Diviš Claus Elstner Rezensent Z. Šimon 《Studia Geophysica et Geodaetica》1979,23(2):114-121
Summary Results of gravity measurements performed in 1977 along a WE-profile situated in the GDR area are discussed. Systematic influences caused by the variations of the hydrologic conditions in the local regions of the observation points reach 100 nm s–2. From the results of the yearly repeated gravity measurements (1970/77) a mean yearly gravity variation of about 20 nm s–2 a–1 was calculated for the sedimentary eastern part of the profile. 相似文献
78.
79.
Production of CH4 and CO2 was quantified in anoxically incubated soil samples taken from an Italian rice field. The rates increased with temperature between 10 and 37°C. The δ13C of the accumulated CO2, CH4 and acetate changed with time in a systematic way. The data were used in mass balance equations to constrain isotopic fractionation factors and pathways of CH4 production. The calculations were further constrained by the determination of 14CH4 production from 14CO2 at steady state. At 50°C, CH4 was exclusively produced from CO2, indicating a fractionation factor of αCO2/CH4 = 1.073. Between 10 and 37°C, the results showed a temporal change in the methanogenic pathway. A relatively high (40-60%) CO2-derived fraction of CH4 production in the beginning was followed by a phase in which contribution of CO2-derived CH4 decreased to low (<15%) values, and ultimately by the steady state phase in which values increased to <40% (the theoretically expected value). The rate of change from one phase to the next increased with temperature. Incubation temperature had a strong effect on the overall fractionation of 13C during the formation and consumption of acetate, with stronger fractionation at low than at high temperature. The results further showed that, especially at low temperatures, fractionation occurred during acetate turnover and acetoclastic methanogenesis, despite the fact that steady-state conditions caused (apparent) substrate-limitation. 相似文献
80.
Simon A. Kattenhorn Conrad J. Schaefer 《Journal of Volcanology and Geothermal Research》2008,170(3-4):181-197
Thermal–mechanical analyses of isotherms in low-volume basalt flows having a range of aspect ratios agree with inferred isotherm patterns deduced from cooling fracture patterns in field examples on the eastern Snake River Plain, Idaho, and highlight the caveats of analytical models of sheet flow cooling when considering low-volume flows. Our field observations show that low-volume lava flows have low aspect ratios (width divided by thickness), typically < 5. Four fracture types typically develop: column-bounding, column-normal, entablature (all of which are cooling fractures), and inflation fractures. Cooling fractures provide a proxy for isotherms during cooling and produce patterns that are strongly influenced by flow aspect ratio. Inflation fractures are induced by lava pressure-driven inflationary events and introduce a thermal perturbation to the flow interior that is clearly evidenced by fracture patterns around them. Inflation fracture growth occurs incrementally due to blunting of the lower tip within viscoelastic basalt, allowing the inflation fracture to pivot open. The final stage of growth involves propagation beyond the blunted tip towards the stress concentration at the tapered tip of a lava core, resulting in penetration of the core that causes quenching of the lava and the formation of a densely fractured entablature. We present numerical models that include the effects of inflation fractures on lava cooling and which support field-based inferences that inflation fractures depress the isotherms in the vicinity of the fracture, cause a subdivision of the lava core, control the location of the final portion of the lava flow to solidify, and cause significant changes in the local cooling fracture orientations. In addition to perturbing isotherms, inflation fractures cause a lava flow to completely solidify in a shorter amount of time than an identically shaped flow that does not contain an inflation fracture. 相似文献