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541.
Carbon capture and storage is a viable greenhouse gas mitigation technology and the Sleipner CO2 sequestration site in the North Sea is an excellent example. Storage of CO2 at the Sleipner site requires monitoring over large areas, which can successfully be accomplished with time lapse seismic imaging. One of the main goals of CO2 storage monitoring is to be able to estimate the volume of the stored CO2 in the reservoir. This requires a parametrization of the subsurface as exact as possible. Here we use elastic 2D time‐domain full waveform inversion in a time lapse manner to obtain a P‐wave velocity constrain directly in the depth domain for a base line survey in 1994 and two post‐injection surveys in 1999 and 2006. By relating velocity change to free CO2 saturation, using a rock physics model, we find that at the considered location the aquifer may have been fully saturated in some places in 1999 and 2006. 相似文献
542.
Manuel Calvo-Rathert Bertha Aguilar Reyes Avto Goguitchaichvili José Rosas Elguera Héctor Franco Juan Morales Ruth Soto Ángel Carrancho Hugo Delgado 《Studia Geophysica et Geodaetica》2013,57(2):309-331
A rock-magnetic and paleomagnetic investigation was carried out on eleven Pleistocene and Pliocene 40Ar/39Ar dated lava flows from the Tepic-Zacoalco rift region in the western sector of the Trans-Mexican Volcanic Belt (TMVB) with the aim of obtaining new paleomagnetic data from the study region and information about the Earth’s magnetic field recorded in these rocks. Rock-magnetic experiments including measurement of thermomagnetic curves, hysteresis parameters and isothermal remanence acquisition curves were carried out to find out the carriers of remanent magnetisation and to determine their domain structure. Although some samples were characterised by the presence of a single ferromagnetic phase (magnetite), in most cases more phases were observed. Analysis of hysteresis parameters showed a mixture of single domain and multidomain particles, the fraction of the latter varying between 40% and 80%. Paleomagnetic results were obtained in all sites, although in 7 sites characteristic remanence directions and remagnetisation circles had to be combined in order to calculate site means. The six Pliocene sites not showing intermediate polarity yielded a paleomagnetic pole (latitude ? = 81.1°, longitude λ = 94.3°) which roughly agrees with the expected one. Paleomagnetic directions do not indicate significant vertical-axis block rotations in the western TMVB area. Reversed polarities observed can be correlated to the Gilbert chron, normal polarities to the Gauss chron or the Brunhes chron and intermediate polarities to the Cochiti-Gilbert or the Gilbert-Gauss transition. The reversed or intermediate polarity magnetisation recorded in one of the sites (542 ± 24 ka) corresponds either to the West Eifel 4 or the West Eifel 5 excursion, while the reversed polarity observed in the other site (220 ± 36 ka) very likely provides new evidence for the Pringle Falls excursion or the event recorded in the Mamaku ignimbrite. 相似文献
543.
Terrestrial Laser Scanners (TLS) provide a non‐contact method to measure soil microtopography of relatively large surface areas. The appropriateness of the technology in relatation to the derived Digital Elevation Models (DEM) however has not been reported. The suitability of TLS for soil microtopography measurements was tested on‐field for three large soil surface areas in agricultural fields. The acquired point clouds were filtered with a custom cloud import algorithm, and converted into digital elevation models (DEM) of different resolutions. To assess DEM quality, point clouds measured from different viewpoints were statistically compared. The statistical fit between point clouds from different viewpoints depends on spatial resolution of the DEM. The best results were obtained at the higher resolutions (0.02 to 0.04 cm), where less than 5 % of the grid cells showed significant differences between one viewpoint and the next (p < 0.01). Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
544.
Manuel Calvo-Rathert Ángel Carrancho Florian Stark Juan José Villalaín Mimi Hill 《Quaternary Research》2012,77(2):326-330
This study tests if burnt soils and sediments can provide reliable records of geomagnetic field strength at the time of burning by carrying out an experiment to reproduce the prehistoric use of fire on a clayish soil substratum. Rock magnetic experiments showed that in the upper 0–1 cm of the central part of the burnt surface, remanence is a thermoremanent magnetization carried by single-domain magnetite and that samples are thermally stable. Fourteen specimens from that area were subjected to paleointensity experiments with the Coe method (1967). An intensity of 42.9 ± 5.7 μT was estimated below 440°C, whereas at higher temperatures magneto-mineralogical alterations were observed. Corresponding successful microwave intensity determinations from two specimens gave a mean value of 47.6 μT. Both results are in reasonable agreement with the expected field value of 45.2 μT. Burnt soils of archeological fires thus have the potential to record accurately the paleofield strength and may be useful targets for archeointensity investigations. Coincident results obtained from two different paleointensity determination methods support this conclusion. 相似文献
545.
Multispecies Mortality Patterns of Commercial Bivalves in Relation to Estuarine Salinity Fluctuation
Fluctuations in salinity may cause huge economic losses in estuaries with exploited commercial bivalves owing to their effect
on mortality of these species. However, the same decrease in salinity does not affect all species in the same way, so it is
interesting to study the effect of salinity from a multispecies standpoint. In the management of exploited bivalve beds, it
is important to know the tolerance thresholds of the species, not only in cases of extremely low salinities but also over
prolonged periods when salinities are low but not extreme. An analysis of mortality episodes of commercial bivalves in the
Ulla River estuary (Galicia, NW Spain) from 1977 to 2009 revealed two mortality patterns related to how greatly the different
species were affected. A mathematical model was designed to estimate salinity in the estuary based on weather conditions and
tidal amplitude. By applying this model, it was possible to deduce the intensity and duration of the salinity decrease in
the days prior to each mortality episode with the goal of relating these factors to mortality patterns. The two parameters
found to be sufficient to explain the mortality observed were the minimum salinity at high tide and the number of consecutive
days below a specific salinity threshold. 相似文献
546.
Muhammad Nadeem Sharif Ashraf Farahat Muhammad A. Al-Zahrani Nilufar Islam Manuel J. Rodriguez Rehan Sadiq 《Arabian Journal of Geosciences》2016,9(9):546
Water quality management in distribution networks is directly related to spatial distribution of chlorine boosters and its dosages. Water chlorination is essential to reduce the effects of bacterial and other microbiological contaminants. A higher dosage of chlorine generates harmful by-products in addition to changes in drinking water’s taste and odor. The optimization of chlorine dosage is necessary to decrease the microbial contaminants that affect water quality. Once the chlorine threshold is determined for microbial contaminant, it will help decision makers suggest optimal values. These decisions can rely on the estimated water quality index (WQI). WQI is an index to evaluate water quality and can be linked to adequate residual chlorine with optimal booster dosage, numbers, and locations in water distribution network (WDN). The city of Al-Khobar, Saudi Arabia’s WDN was selected to validate the application of this study. Based on geographic location, the city Al-Khobar water network was divided into five zones. The initial temporal and spatial analysis pointed out poor water quality zones. EPANET, a modeling and simulating software, was applied to evaluate the WQI. Those EPANET results were then integrated with an optimization model. The optimization model suggested new chlorine booster locations to improve water quality in the city of Al-Khobar water distribution network. 相似文献
547.
Manuel M. González‐Duarte Cesar Megina Doris De Vito Cristina Goia Di Camillo Stefania Puce Stefano Piraino 《Marine Ecology》2016,37(1):155-163
Hydroids are important components of the communities of rocky bottom shallow coastal areas. The hydrozoan fauna of the Mediterranean Sea is probably one of most investigated in the world, with lots of faunistic and biogeographical studies. However, quantitative studies using the same sampling methodology and controlled sampling effort have been restricted to areas in the Western and Central Mediterranean. We compared hydroid assemblages in four areas of the Mediterranean Sea, from the Gulf of Cádiz to the South Adriatic Sea, following the same sampling and quantification methodology. Our analysis showed the dominant Atlantic character of the assemblages of the Gulf of Cádiz and the South Alboran Sea because of the influence of the inflowing Atlantic waters. Conversely, the hydroid assemblages of the North Alboran Sea were more similar to the assemblages in the Ligurian and in the South Adriatic, and with a number of species ranking between the observed in these two Mediterranean zones. Fourteen species were identified as making the most significant contributions to characterizing the Mediterranean hydroid species pool from a quantitative point of view. These taxa include species previously named as typical components of the Mediterranean hydroid fauna as well as those only recently recorded in the region (Eudendrium moulouyensis) and invaders such as Clytia hummelincki. 相似文献
548.
Mathias Versichele Tijs Neutens Manuel Claeys Bouuaert Nico Van de Weghe 《Transactions in GIS》2014,18(5):687-703
Certain datasets on moving objects are episodic in nature – that is, the data is characterized by time gaps during which the position of the object is unknown. In this article, a model is developed to study the sparsely sampled network‐constrained movement of several objects by calculating both potential and feasible (i.e. more likely) co‐presence opportunities over time. The approach is applied to the context of a static sensor network, where the location of an object is only registered when passing a sensor location along a road network. Feasibility is incorporated based on the deviation from the shortest path. As an illustration, the model is applied to a large Bluetooth tracking dataset gathered at a mass event. The model output consists of maps showing the temporal evolution of the distribution of feasible co‐presence opportunities of tracked visitors over the network (i.e. the number of visitors that could have been present together). We demonstrate the model's usefulness in studying the movement and distribution of a crowd over a study area with relatively few sampling locations. Finally, we discuss the results with a special emphasis on the distinction between feasible and actual presence, the need for further validation and calibration, and the performance of the implementation. 相似文献
549.
Maya García-Comas Manuel López-Puertas Bianca M. Dinelli Alberto Adriani Angioletta Coradini 《Icarus》2011,214(2):571-583
After molecular nitrogen, methane is the most abundant species in Titan’s atmosphere and plays a major role in its energy budget and its chemistry. Methane has strong bands at 3.3 μm emitting mainly at daytime after absorption of solar radiation. This emission is strongly affected by non-local thermodynamic equilibrium (non-LTE) in Titan’s upper atmosphere and, hence, an accurate modeling of the non-LTE populations of the emitting vibrational levels is necessary for its analysis. We present a sophisticated and extensive non-LTE model which considers 22 CH4 levels and takes into account all known excitation mechanisms in which they take part. Solar absorption is the major excitation process controlling the population of the v3-quanta levels above 1000 km whereas the distribution of the vibrational energy within levels of similar energy through collisions with N2 is also of importance below that altitude. CH4-CH4 vibrational exchange of v4-quanta affects their population below 500 km. We found that the ν3 → ground band dominates Titan’s 3.3 μm daytime limb radiance above 750 km whereas the ν3 + ν4 → ν4 band does below that altitude and down to 300 km. The ν3 + ν2 → ν2, the 2ν3 → ν3, and the 13CH4ν3 → ground bands each contribute from 5% to 8% at regions below 800 km. The ν3 + 2ν4 → 2ν4and ν2 + ν3 + ν4 → ν2 + ν4 bands each contribute from 2% to 5% below 650 km. Contributions from other CH4 bands are negligible. We have used the non-LTE model to retrieve the CH4 abundance from 500 to 1100 km in the southern hemisphere from Cassini-VIMS daytime measurements near 3.3 μm. Our retrievals show good agreement with previous measurements and model results, supporting a weak deviation from well mixed values from the lower atmosphere up to 1000 km. 相似文献
550.
Implementation and integrated numerical modeling of a landslide early warning system: a pilot study in Colombia 总被引:3,自引:2,他引:1
Christian Huggel Nikolay Khabarov Michael Obersteiner Juan Manuel Ramírez 《Natural Hazards》2010,52(2):501-518
Landslide early warning systems (EWS) are an important tool to reduce landslide risks, especially where the potential for
structural protection measures is limited. However, design, implementation, and successful operation of a landslide EWS is
complex and has not been achieved in many cases. Critical problems are uncertainties related to landslide triggering conditions,
successful implementation of emergency protocols, and the response of the local population. We describe here the recent implementation
of a landslide EWS for the Combeima valley in Colombia, a region particularly affected by landslide hazards. As in many other
cases, an insufficient basis of data (rainfall, soil measurements, landslide event record) and related uncertainties represent
a difficult complication. To be able to better assess the influence of the different EWS components, we developed a numerical
model that simulates the EWS in a simplified yet integrated way. The results show that the expected landslide-induced losses
depend nearly exponentially on the errors in precipitation measurements. Stochastic optimization furthermore suggests an increasing
adjustment of the rainfall landslide-triggering threshold for an increasing observation error. These modeling studies are
a first step toward a more generic and integrated approach that bears important potential for substantial improvements in
design and operation of a landslide EWS. 相似文献