From noise correlation to resonant ultrasound spectroscopy in rock acoustics          下载免费PDF全文

Sandra Barbouteau  Patrick Rasolofosaon  Noalwenn Dubos‐Sallée  Virginie Vassil  Valérie Poitrineau  Jean‐François Nauroy 《Geophysical Prospecting》2016,64(5):1368-1385

This article introduces an alternative experimental procedure for measuring the elastic properties of a solid material at laboratory scale, using both the principles of passive seismic interferometry and resonance ultrasound spectroscopy. We generate noise into the studied sample with a pneumatic air blow gun, and we cross‐correlate the signals recorded with two passive piezoelectric sensors put in soft contact with the sample surface. Resonance phenomena are induced in the sample, but in contrast with conventional resonance ultrasound spectroscopy experiments, we have no control over the injected frequencies that are sent all together within the noise spectrum. The spectrum of the correlogram is a good approximation of the resonance spectrum of the vibrating sample and can be inverted in terms of the elastic moduli of the constituent material of the sample. The experimental procedure is validated on samples made of standard materials (here, aluminium and Plexiglas) by consistently comparing the inverted elastic velocities with the velocities independently measured with the conventional technique of ultrasonic pulse transmission. Moreover, we got similar positive results on dry rock samples, such as Vilhonneur limestone. These encouraging preliminary results open up promising prospects for monitoring fluid substitution in rock samples using the technique described in this paper.  相似文献   

Shell use by sympatric hermit crab species in a seasonally open coastal lagoon in Northeastern Brazil          下载免费PDF全文

Valéria F. Vale  Sávio A. S. N. Moraes  Vanessa L. G. Brito  Carlos E. R. D. Alencar  Fúlvio A. M. Freire 《Marine Ecology》2017,38(5)

There are gaps in what is known about the patterns of gastropod shell use by hermit crabs in Brazilian lagoon areas, especially in Northeastern Brazil. However, this is important because the understanding of selection patterns provides information on life history and eco‐evolutionary conceptions of paguroids. The present study investigated the use of gastropod shells occupied by Pagurus criniticornis and Clibanarius sclopetarius in a coastal lagoon seasonally connected to an estuary and to the sea, correlating eco‐evolutionary aspects and hydrodynamic characters. The study was carried out between February 2013 and January 2014. Hermit crabs and their shells were identified and measured (hermit crabs’ cephalothorax shield length and width, major propodus length and height, weight, shell total length and width, shell aperture length and width). Partial least squares regression was used to analyse the morphometric data. Additionally, a multinomial proportions test was performed to infer patterns (inter‐/intra‐specific) of shells’ occupation. Hermit crab species occupied a total of 13 types of shells, predominantly those of Neritina virginea (67.83%). The shell weight was the most important determinant of shell occupancy in the morphometric model (variable importance in projection >1). The proportions of N. virginea shells used were similar in both species of hermit crabs, except between the sexes of P. criniticornis. Presumably, the high utilization rate of N. virginea shells is related to its abundance and dispersal, and to the shells’ suitability for hermit crabs, which is reflected by the morphometric model, as well as by the hydrodynamics of the lagoon‐estuarine environment. The relative occupation of different types of shells for each species of hermit crabs studied appears to be associated with regulation by inter‐/intra‐specific competition, which fosters the co‐occurrence of those populations. These results endorse coastal lagoons as a refuge and recruitment area for aquatic fauna. In addition, it highlights a challenge in the management and conservation of paguroid species whose population dynamics depend on the resources coming from the Gastropoda community.  相似文献   

The international workshop on wave hindcasting and forecasting and the coastal hazards symposium   总被引：1，自引：1，他引：0  

Øyvind Breivik  Val Swail  Alexander V. Babanin  Kevin Horsburgh 《Ocean Dynamics》2015,65(5):761-771

  相似文献   

Gravity data as a tool for landfill study     

João B. C. Silva  Wlamir A. Teixeira  Valéria C. F. Barbosa 《Environmental Geology》2009,57(4):749-757

This paper shows the potential of gravity data to map a buried landfill bottom topography. To this end, a gravity inversion method is presented for estimating the landfill’s bottom depths at discrete points assuming a decrease of the density contrast with depth according to a hyperbolic law. The method’s efficiency was tested using synthetic data from simulated waste landfills, producing estimated bottom topographies very close to the true ones. The method’s potentiality has been further evaluated in applying it to the gravity data from the abandoned Thomas Farm Landfill site, Indiana, USA, whose bottom topography is known. The estimated topography showed close agreement with the known Thomas Farm Landfill’s bottom topography.  相似文献   

The measurement of D/H ratio in alkenones and their isotopic heterogeneity     

Valérie F. Schwab  Julian P. Sachs 《Organic Geochemistry》2009,40(1):111-118

Previous paleoenvironmental studies reported the δD values of a mixture of coeluting alkenones. Here, we present a semi-preparative normal-phase high-performance liquid chromatography–mass spectrometry (NP-HPLC–MS) method for purifying long chain (C₃₇ and C₃₈) unsaturated methyl and ethyl ketones (alkenones) on the basis of chain length and degree of unsaturation.The method was applied to purify alkenones in suspended particles and surface sediments from a site in Chesapeake Bay, eastern USA. The hydrogen isotopic composition of di- and triunsaturated C₃₇ and C₃₈ alkenones differed significantly on the basis of chain length and the degree of unsaturation, demonstrating the importance of gas chromatography–isotope ratio-mass spectrometry (GC–irMS) analysis of individual alkenones for accurate paleoenvironmental reconstruction. Constant fractionation factors between alkenones with different chain length but the same degree of unsaturation (${\alpha }_{{\text{C}}_{37:2}''–''{\text{C}}_{38:2}}\text{and}{\alpha }_{{\text{C}}_{37:3}''–''{\text{C}}_{38:3}}=1.01$) and those with the same chain length but different degree of unsaturation (${\alpha }_{{\text{C}}_{37:2}''–''{\text{C}}_{37:3}}\text{and}{\alpha }_{{\text{C}}_{38:2}''–''{\text{C}}_{38:3}}=0.97$) in all samples suggest that the values may represent hydrogen isotope fractionation associated with elongation and desaturation during alkenone biosynthesis.  相似文献   

The Effect of the Great Barrier Reef on the Propagation of the 2007 Solomon Islands Tsunami Recorded in Northeastern Australia     

Toshitaka Baba  Richard Mleczko  David Burbidge  Phil R. Cummins  Hong Kie Thio 《Pure and Applied Geophysics》2008,165(11-12):2003-2018

The effect of offshore coral reefs on the impact from a tsunami remains controversial. For example, field surveys after the 2004 Indian Ocean tsunami indicate that the energy of the tsunami was reduced by natural coral reef barriers in Sri Lanka, but there was no indication that coral reefs off Banda Aceh, Indonesia had any effect on the tsunami. In this paper, we investigate whether the Great Barrier Reef (GBR) offshore Queensland, Australia, may have weakened the tsunami impact from the 2007 Solomon Islands earthquake. The fault slip distribution of the 2007 Solomon Islands earthquake was firstly obtained by teleseismic inversion. The tsunami was then propagated to shallow water just offshore the coast by solving the linear shallow water equations using a staggered grid finite-difference method. We used a relatively high resolution (approximately 250 m) bathymetric grid for the region just off the coast containing the reef. The tsunami waveforms recorded at tide gauge stations along the Australian coast were then compared to the results from the tsunami simulation when using both the realistic 250 m resolution bathymetry and with two grids having fictitious bathymetry: One in which the the GBR has been replaced by a smooth interpolation from depths outside the GBR to the coast (the “No GBR” grid), and one in which the GBR has been replaced by a flat plane at a depth equal to the mean water depth of the GBR (the “Average GBR” grid). From the comparison between the synthetic waveforms both with and without the Great Barrier Reef, we found that the Great Barrier Reef significantly weakened the tsunami impact. According to our model, the coral reefs delayed the tsunami arrival time by 5–10 minutes, decreased the amplitude of the first tsunami pulse to half or less, and lengthened the period of the tsunami.  相似文献   

Trace metals and benthic macrofauna distributions in Camamu Bay, Brazil: sediment quality prior oil and gas exploration     

Hatje V  Barros F  Magalhães W  Riatto VB  Amorim FN  Figueiredo MB  Spanó S  Cirano M 《Marine pollution bulletin》2008,56(2):363-370

  相似文献   

Spawning migrations, sexual maturity and sex steroid levels in female roach Rutilus rutilus from the River Meuse     

Patrick Kestemont  Jacques Rinchard  Valérie Feys  Alexis Fostier 《Aquatic Sciences - Research Across Boundaries》1999,61(2):111-121

  相似文献   

Absolute seafloor vertical positioning using combined pressure gauge and kinematic GPS data   总被引：1，自引：0，他引：1  

Valérie Ballu  Marie-Noelle Bouin  Stéphane Calmant  Eric Folcher  Jean-Michel Bore  Jérome Ammann  Olivier Pot  Michel Diament  Bernard Pelletier 《Journal of Geodesy》2010,84(1):65-77

Knowledge of the position and motion of points on the seafloor can be critically important in both fundamental research (for example, global geodesy and plate tectonics) and for more practical applications such as seismic risk evaluation, off-shore construction and pipeline monitoring. In the Vanuatu subduction zone, for example, measuring deformation underwater could provide valuable information for modeling deformation and understanding the seismic cycle. We report a shallow water experiment in Vanuatu to measure the relative and absolute depth of seafloor points. The experiment differs from previous efforts mainly in that it uses the height of the sea surface determined by kinematic GPS, allowing us to locate the points in a global reference frame. The ITRF2005 ellipsoidal height of a seafloor benchmark was determined with a 1-sigma uncertainty of 0.7–2.1 cm. The estimated ellipsoidal height differs only by a few tenths of a centimeter between measurements made in 2004 and another set made in 2006. These results are encouraging and open new perspectives for vertical underwater deformation monitoring in shallow water areas. Sea-surface GPS measurements can also help to reduce the uncertainty in depth difference determination for relative measurements.  相似文献   

Morphological controls on the dynamics of carbonate landscapes under a mediterranean climate          下载免费PDF全文

Franck Thomas  Vincent Godard  Olivier Bellier  Esmaeil Shabanian  Vincent Ollivier  Lucilla Benedetti  Magali Rizza  Nicolas Espurt  Valéry Guillou  Fabrice Hollender  Stéphane Molliex  ASTER Team 《地学学报》2017,29(3):173-182

The influence of the morphological setting on the denudation of carbonate landscapes and the respective contributions of mechanical and chemical weathering processes are still debated. We have addressed these questions by measuring ³⁶Cl concentrations in 40 samples from the Luberon mountain, SE France, to constrain the denudation of various landscape elements. We observe a clear contrast between the local denudation rates from the flat summit surface, clustered around 30 mm/ka, and the basin‐average denudation rates across the flanks, ranging from 100 to 200 mm/ka. This difference highlights the transient evolution of the range, whose topography is still adjusting to previous uplift events. Such a pattern also suggests that carbonate dissolution is not the only driver of denudation in this setting, which appears to be significantly controlled by slope‐dependent processes.  相似文献