Source wavelet correction for practical Marchenko imaging: A sub-salt field-data example from the Gulf of Mexico     

Constantin Mildner  Filippo Broggini  Carlos Alberto da Costa Filho  Johan O.A. Robertsson 《Geophysical Prospecting》2019,67(8):2085-2103

Imaging a target zone below a salt body can be challenging because large velocity contrasts in the overburden between the salt and surrounding sediments generate internal multiples, which interfere with primary reflections from the target level in the imaging process. This can lead to an erroneous interpretation of reflections in the sub-salt area if multiples are misinterpreted as primaries. The Marchenko redatuming method may enable imaging of the sub-salt target area where the effect of the multiply-scattering overburden is removed. This is achieved by creating a redatumed reflection response where virtual sources and receivers are located below the overburden using a macromodel of the velocity field and the surface reflection data. The accuracy of the redatumed data and the associated internal multiple removal, however, depends on the accurate knowledge of the source wavelet of the acquired reflection data. For the first time, we propose a method which can accurately and reliably correct the amplitudes of the reflection response in field data as required by the Marchenko method. Our method operates by iteratively and automatically updating the source function so as to cancel the most artefact energy in the focusing functions, which are also generated by the Marchenko method. We demonstrate the method on a synthetic dataset and successfully apply it to a field dataset acquired in a deep-water salt environment in the Gulf of Mexico. After the successful source wavelet estimation for the field dataset, we create sub-salt target-oriented images with Marchenko redatumed data. Marchenko images using the proposed source wavelet estimation show clear improvements, such as increased continuity of reflectors, compared to surface-based images and to conventional Marchenko images computed without the inverted source wavelet. Our improvements are corroborated by evidence in the literature and our own synthetic results.  相似文献   

In situ experimental study of reed leaf decomposition along a full salinity gradient     

Victor Quintino  Franca Sangiorgio  Fernando Ricardo  Renato Mamede  Adília Pires  Rosa Freitas  Ana Maria Rodrigues  Alberto Basset 《Estuarine, Coastal and Shelf Science》2009

An experimental study on Phragmites australis leaf litter decomposition was conducted in the estuarine environment, Ria de Aveiro, Western Portugal, using the leaf-bag technique, with fine- (1 mm) and coarse-mesh (5 mm) bags. The leaf bags were placed in the field sites at day 0, covering a complete salinity gradient, and replicates were collected over time, at days 3 (leaching), 7, 15, 30 and 60. The biomass loss through the leaching phase, about 20% of the initial leaf mass, was independent of both the salinity and the bag mesh size. The biomass decay pattern along the salinity gradient varied through time and presented strong similarities between the two mesh sizes, with the remaining biomass always lower in the 5 mm mesh-size bags. At days 7 and 15, the lowest remaining biomass was observed at the head of the estuary, the preferential distribution area of P. australis. At day 30, the remaining biomass was higher in the marine area and diminished under a direct relationship with salinity, reaching the lowest value in the freshwater environment, with values ranging from 66% to 44% of the initial weight in 5 mm bags, and from 79% to 51% in 1 mm bags. The largest heterogeneity in the remaining biomass among the study areas positioned along the salinity gradient was found close to days 30 (5 mm) and 40 (1 mm). The overall results indicate that the relationship between leaf decay rate and salinity depends on the decay time considered (k₁₅, k₃₀ or k₆₀) and, for the later stages (k₆₀), also on the leaf-bag mesh size. This implies that the use of leaf litter decay rates as a functional indicator in transitional waters will need to take into consideration the factor location in the salinity gradient and leaf litter stage at which the decay rate is determined. The differences between the decay rates with the mesh size acted mainly at the level of the absolute k value and not at the level of the pattern along the salinity gradient. Even so, the data obtained at the mouth of the estuary, in the area closest to a fully marine environment, indicated that after the initial biomass loss through leaching, P. australis decayed either very slowly, in the 5 mm, or not at all, in the 1 mm mesh bags.  相似文献   

Volcanic stratigraphy of a high-altitude Mammuthus columbi (Tlacotenco,Sierra Chichinautzin), Central México     

Marie-Noelle Guilbaud  Lilia Arana-Salinas  Claus Siebe  Luis Alberto Barba-Pingarrón  Agustín Ortiz 《Bulletin of Volcanology》2015,77(3):1-16

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Drainage network detection and assessment of network storage capacity in agrarian landscape     

Federico Cazorzi  Giancarlo Dalla Fontana  Alberto De Luca  Giulia Sofia  Paolo Tarolli 《水文研究》2013,27(4):541-553

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Three-Dimensional Reconstruction and Thermal Modeling of Observed Loops     

Nuevo  Federico A.  Mac Cormack  Cecilia  López Fuentes  Marcelo C.  Vásquez  Alberto M.  Mandrini  Cristina H. 《Solar physics》2020,295(12):1-22

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Comment on “Effect of surface wave inversion non-uniqueness on 1D seismic ground response analysis” by Roy et al.     

Alberto Pettiti  Sebastiano Foti  Cesare Comina 《Natural Hazards》2015,75(1):975-981

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Consistency Problems in the Improvement of the IAU Precession–Nutation Theories: Effects of the Dynamical Ellipticity Differences     

Alberto Escapa  José M. Ferrándiz  Tomás Baenas  Juan Getino  Juan F. Navarro  Santiago Belda–Palazón 《Pure and Applied Geophysics》2016,173(3):861-870

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Which policy instruments attract foreign direct investments in renewable energy?     

Ronald Wall  Alberto Gianoli  Spyridon Stavropoulos 《Climate Policy》2019,19(1):59-72

Reducing GHG emissions and mitigating climate change would require significant investments in renewable energy technologies. Foreign direct investments (FDI) in renewable energy (RE) have increased over the last years, contributing to the diffusion of RE globally. In the field of climate policy, there are multiple policy instruments aimed at attracting investments in renewable energy. This article aims to map the FDI flows globally including source and destination countries. Furthermore, the article investigates which policy instruments attract more FDI in RE sectors such as solar, wind and biomass, based on an econometric analysis of 137 Organisation for Economic Co-operation and Development (OECD) and non-OECD countries. The results show that Feed in Tariffs (FIT) followed by Fiscal Measures (FM), such as tax incentives and Renewable Portfolio Standards (RPS), are the most significant policy instrument that attract FDI in the RE sector globally. Regarding carbon pricing instruments, based on our analysis, carbon tax proved to be correlated with high attraction of FDI in OECD countries, whereas Emissions Trading Schemes (ETS) proved to be correlated with high attraction of FDI mainly in non-OECD countries.

Key policy insights

• Feed in Tariffs is the most significant policy instrument that attracts FDI in the Renewable Energy sector globally.

• Fiscal Measures (FM), such as tax incentives, show a significant and positive impact on renewable energy projects by foreign investors, and particularly on solar energy.

• Carbon pricing instruments, such as carbon taxation and emissions trading, proved to attract FDI in OECD and non-OECD countries respectively.

• Public investments, such as government funds for renewable energy projects, proved not as attractive to foreign private investors, perhaps because public funds are not perceived as stable in the long run.

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Modeling of Landslides in Valles Marineris,Mars, and Implications for Initiation Mechanism     

Meaza Tsige  Javier Ruiz  Ian A. del Río  Alberto Jiménez-Díaz 《Earth, Moon, and Planets》2016,118(1):15-26

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High crustal diversity preserved in the lunar meteorite Mount DeWitt 12007 (Victoria Land,Antarctica)          下载免费PDF全文

Alberto Collareta  Massimo D'Orazio  Maurizio Gemelli  Andreas Pack  Luigi Folco 《Meteoritics & planetary science》2016,51(2):351-371

The meteorite Mount DeWitt (DEW) 12007 is a polymict regolith breccia mainly consisting of glassy impact‐melt breccia particles, gabbroic clasts, feldspathic clasts, impact and volcanic glass beads, basaltic clasts, and mingled breccia clasts embedded in a matrix dominated by fine‐grained crystals; vesicular glassy veins and rare agglutinates are also present. Main minerals are plagioclase (typically An_>85) and clinopyroxene (pigeonites and augites, sometimes interspersed). The presence of tranquillityite, coupled with the petrophysical data, the O‐isotope data (Δ¹⁷O = ?0.075), and the FeO_tot/MnO ratios in olivine (91), pyroxene (65), and bulk rock (77) indicate a lunar origin for DEW 12007. Impactites consist of Al‐rich impact‐melt splashes and plagioclase‐rich meta‐melt clasts. The volcanic products belong to the very low titanium (VLT) or low titanium (LT) suites; an unusual subophitic fragment could be cryptomare‐related. Gabbroic clasts could represent part of a shallow intrusion within a volcanic complex with prevailing VLT affinity. DEW 12007 has a mingled bulk composition with relatively high incompatible element abundances and shows a high crustal diversity comprising clasts from the Moon's major terranes and rare lithologies. First‐order petrographic and chemical features suggest that DEW 12007 could be launch‐paired with other meteorites including Y 793274/981031, QUE 94281, EET 87521/96008, and NWA 4884.  相似文献