Additions to the deep‐sea fishes of New Zealand     

Charles McCann 《新西兰海洋与淡水研究杂志》2013,47(4):619-640

  相似文献   

Acoustic and petrophysical relationships in low-shale sandstone reservoir rocks     

Jalal Khazanehdari  Clive McCann 《Geophysical Prospecting》2005,53(4):447-461

This paper describes the measurements of the acoustic and petrophysical properties of two suites of low‐shale sandstone samples from North Sea hydrocarbon reservoirs, under simulated reservoir conditions. The acoustic velocities and quality factors of the samples, saturated with different pore fluids (brine, dead oil and kerosene), were measured at a frequency of about 0.8 MHz and over a range of pressures from 5 MPa to 40 MPa. The compressional‐wave velocity is strongly correlated with the shear‐wave velocity in this suite of rocks. The ratio V_P/V_S varies significantly with change of both pore‐fluid type and differential pressure, confirming the usefulness of this parameter for seismic monitoring of producing reservoirs. The results of quality factor measurements were compared with predictions from Biot‐flow and squirt‐flow loss mechanisms. The results suggested that the dominating loss in these samples is due to squirt‐flow of fluid between the pores of various geometries. The contribution of the Biot‐flow loss mechanism to the total loss is negligible. The compressional‐wave quality factor was shown to be inversely correlated with rock permeability, suggesting the possibility of using attenuation as a permeability indicator tool in low‐shale, high‐porosity sandstone reservoirs.  相似文献   

Seismic velocities in fractured rocks: an experimental verification of Hudson's theory1     

S. Peacock  C. McCann  J. Sothcott  T.R. Astin 《Geophysical Prospecting》1994,42(1):27-80

Flow of fluids in many hydrocarbon reservoirs and aquifers is enhanced by the presence of cracks and fractures. These cracks could be detected by their effects on propagation of compressional and shear waves through the reservoir: several theories, including Hudson's, claim to predict the seismic effects of cracks. Although Hudson's theory has already been used to calculate crack densities from seismic surveys, the predictions of the theory have not yet been tested experimentally on rocks containing a known crack distribution. This paper describes an experimental verification of the theory. The rock used, Carrara marble, was chosen for its uniformity and low porosity, so that the effect of cracks would not be obscured by other influences. Cracks were induced by loading of laboratory specimens. Velocities of compressional and shear waves were measured by ultrasound at 0.85 MHz in dry and water-saturated specimens at high and low effective pressures. The cracks were then counted in polished sections of the specimens. In ‘dry’ specimens with both dry and saturated cracks, Hudson's theory overpredicted observed crack densities by a constant amount that is attributed to the observed value being systematically underestimated. The theory made poor predictions for fully saturated specimens. Shear-wave splitting, caused by anisotropy due to both crystal and crack alignment, was observed. Cracks were seen to follow grain boundaries rather than the direction of maximum compression due to loading. The results demonstrate that Hudson's theory may be used in some cases to determine crack and fracture densities from compressional- and shear-wave velocity data.  相似文献   

Spatial seismicity variations along convergent plate boundaries     

R. E. Habermann  W. R. McCann  B. Perin 《Geophysical Journal International》1986,85(1):43-68

Summary. Five major convergent plate boundaries (South America, Izu–Bonin–Marianas, New Hebrides, Tonga–Kermadec and Indonesia) show strong variations in levels of background seismicity on scales ranging from tens to thousands of kilometres. These variations were tested using two statistical approaches and we conclude that small earthquakes are not distributed randomly along these zones.
Two types of large-scale seismicity variations (termed first order) were recognized. First, regions with dimensions on the order of 100 km with extremely high seismicity levels (first-order actives). One such region was recognized in each of the zones studied. Second, large-scale (500 to several thousand kilometres) differences in the level of background seismicity along a given plate boundary. Regions with consistent levels of background seismicity are termed first-order segments.
We examined each first-order segment for smaller scale variations. Ten regions ranging in length from 40 to 170 km with anomalously high seismicity levels were recognized. Fifty-three regions ranging in length from 25 to 355 km were found to have anomalously low seismicity levels. Thus, areas with anomalously high levels of activity are rare in subduction zones.
These observations indicate that background seismicity in subduction zones is not randomly distributed along the strike of the zones. It seems likely that the observed variations reflect tectonic differences. In fact, many of the seismicity variations which we observed appear to be spatially related to features on the seafloor or on the overriding plate. If this is so, then they may provide a powerful tool for characterizing subduction zones and understanding the mechanisms of earthquake generation.  相似文献   

Middle to Late Devonian basin evolution in the Rügen area,NE Germany     

McCann  Tommy 《Geologie en Mijnbouw》1999,78(1):57-71

The Middle to lower Upper Devonian succession of the Rügen Depression in NE Germany consists of largely clastic sediments, whereas the Upper Devonian deposits are mixed carbonate and clastic. Petrographic and geochemical data suggest that the sediments were deposited in a cratonic or recycled setting. Deposition was largely confined to a fault-bounded basin, located between two structural highs. During the Devonian, the Rügen area underwent evolution from a continental and marginal marine area during the Eifelian-early Frasnian to a deeper marine environment during the late Frasnian-early Famennian. By the latest Famennian, an open-shelf carbonate-facies environment was established.  相似文献   

Provenance of Miocene sandstones in northern Iraq: constraints from framework petrography,bulk-rock geochemistry and mineral chemistry     

A.I. Al-Juboury  T. McCann  M.M. Ghazal 《Russian Geology and Geophysics》2009,50(6):517-534

Modal analysis, bulk-rock geochemistry and phase chemistry of sandstones of the Miocene Fat'ha and Injana formations, northern Iraq, show that the clastics were derived from heterogeneous sources that include basic igneous and metamorphic rocks as well as older sedimentary rocks. The sandstones are generally carbonate-rich lithic arenites. Their geochemistry supports the petrographic results and indicates that they are all Fe-rich, lithic or quartz arkosic sandstones. According to geochemical data, garnets are derived from metamorphic sources, hornblende is of igneous origin, and clinopyroxenes, are produced by basic igneous rocks. Epidote is most probably to be a product of disintegration of metamorphic rocks, essentially, metamorphosed igneous rocks. Rutile geochemistry implies low-grade metamorphic and basic to ultrabasic igneous sources. Chemical composition of chromian spinels indicates that they are derived from Alpine-type peridotite. The ophiolitic-radiolarite belts of Taurus-Zagros as well as the uplifted Cretaceous and Paleocene strata of north and northeastern Iraq are likely to be the major source of clastics to the Fat'ha–Injana basin, a foreland basin formed as a result of the continental Arabian and Turkish/Iranian plates collision.  相似文献   

First southern hemisphere record of the platylepadine barnacle stomatolepas elegans (costa) and notes on the host dermochelys coriacea (Linné)     

Charles McCann 《新西兰海洋与淡水研究杂志》2013,47(1):152-158

The first Southern Hemisphere occurrence of the platylepadine barnacle Stomatolepas elegans (Costa) is recorded. The host animal was a young leather‐back turtle (Dermochelys coriacea (Linné)) .  相似文献   

Use of Al xii and Mg xi lines as solar plasma diagnostics     

B. J. I. Bromage  K. J. H. Phillips  F. P. Keenan  S. M. McCann 《Solar physics》1989,124(2):289-302

We present three sets of observations of n = 1 to n = 2 lines due to helium-like aluminium (Alxii), made during two solar flares (25 August, 1980 and 19 October, 1986), using the X-Ray Polychromator on the SMM satellite. The observed temperature-sensitive line ratio G is shown to be consistent with the close-coupling calculations of Keenan and McCann (1987), although the ratio R, which is both temperature and density-sensitive for lower-Z elements, is not sufficiently well determined from these data to say more than that the observed values of R are not inconsistent with the theoretical calculations. This region of the spectrum also includes the helium-like magnesium (Mgxi) 1¹ S - 3¹ P line, and it is shown that the ratio of this line to the Alxii resonance (1¹ S - 2¹ P) line is a more sensitive indicator of electron temperature than are the Alxii G and R ratios. We demonstrate that the three ratios may be used together in order to derive values of emission measure, electron temperature and electron density during these flares.  相似文献   

Theoretical emission line strengths for the beryllium-like ion Sxiii compared to XUV observations of solar flares     

F. P. Keenan  S. M. McCann  K. G. Widing 《Solar physics》1988,117(1):69-75

A comparison of Skylab S082A observations for several solar flares with calculations of the electron temperature sensitive emission line ratio R ₁ = I(2s2p ¹ P – 2s ^{2 1} S)/I(2s2p ³ P ₁ - 2s ^{2 1} S) = = I(256.68 Å)/I(491.45 Å) in Be-like SXIII reveals good agreement between theory and experiment, which provides observational support for the accuracy of the adopted atomic data. However, observed values of the electron density sensitive ratio R ₂ = I(2s2p ¹ P – 2s ^{2 1} S)/I(2p ^{2 3} P ₂ - 2s2p ³ P ₂) = = I(256.68 Å)/I(308.96 Å) all lie below the theoretical high density limit, which is probably due to blending in the 308.96 Å line.  相似文献   

A laboratory study of seismic velocity and attenuation anisotropy in near-surface sedimentary rocks   总被引：4，自引：0，他引：4  

Angus I. Best  Jeremy Sothcott  Clive McCann 《Geophysical Prospecting》2007,55(5):609-625

The laboratory ultrasonic pulse‐echo method was used to collect accurate P‐ and S‐wave velocity (±0.3%) and attenuation (±10%) data at differential pressures of 5–50 MPa on water‐saturated core samples of sandstone, limestone and siltstone that were cut parallel and perpendicular to the vertical borehole axis. The results, when expressed in terms of the P‐ and S‐wave velocity and attenuation anisotropy parameters for weakly transversely isotropic media (ɛ, γ, ɛ_Q, γ_Q) show complex variations with pressure and lithology. In general, attenuation anisotropy is stronger and more sensitive to pressure changes than velocity anisotropy, regardless of lithology. Anisotropy is greatest (over 20% for velocity, over 70% for attenuation) in rocks with visible clay/organic matter laminations in hand specimens. Pressure sensitivities are attributed to the opening of microcracks with decreasing pressure. Changes in magnitude of velocity and attenuation anisotropy with effective pressure show similar trends, although they can show different signs (positive or negative values of ɛ, ɛ_Q, γ, γ_Q). We conclude that attenuation anisotropy in particular could prove useful to seismic monitoring of reservoir pressure changes if frequency‐dependent effects can be quantified and modelled.  相似文献