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We used recently collected bathymetric data and published gravity data to examine the effective elastic thickness of the lithosphere and the crustal thickness beneath the Ojin Rise Seamounts, located east of Shatsky Rise in the no...
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We used recently collected bathymetric data and published gravity data to examine the effective elastic thickness of the lithosphere and the crustal thickness beneath the Ojin Rise Seamounts, located east of Shatsky Rise in the northwest Pacific Ocean. An admittance analysis of the bathymetric and gravity data indicates that the effective elastic thickness of the Pacific plate under the Ojin Rise Seamounts is 2.7?±?0.1?km, implying that the seamounts were formed on or near the spreading ridge between the Pacific and Farallon plates. The mean crustal thickness beneath the seamounts estimated from the mantle Bouguer anomaly is 10.1?±?1.7?km, which is thicker than the surrounding crust. The thick crust was probably formed by the interaction between the Pacific–Farallon ridge and a hotspot forming Shatsky Rise. Our results indicate that late-stage volcanism after the formation of the main edifices of Shatsky Rise spread widely beyond the eastern side of the rise, forming the Ojin Rise Seamounts.
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We have theoretically investigated the spin-valley asymmetric transport of massive Dirac fermions in the field -controllable bilayer silicene superlattices. The spin-valley dependent ballistic transmission, conductance, and polari...
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We have theoretically investigated the spin-valley asymmetric transport of massive Dirac fermions in the field -controllable bilayer silicene superlattices. The spin-valley dependent ballistic transmission, conductance, and polarization have been systematically calculated by formulating the scattering matrix method for the completed four-band low-energy effective Hamiltonian. Our results uncover that for a single valley transport, near-perfect spin polarization and its perfect switching could be efficiently modulated by the gate field engineering. Under the one-dimensional periodic field modulation, two types of flat bands with less dispersion and, importantly, the perfect contrast in the spin-dependent subbands are observed for the bilayer silicene superlattice. Together with its larger spin-orbit coupling and better stability, these spin-valley asymmetric characteristics engineered by the gate field indicate that the field-controllable bilayer silicene could be a potential component candidate to achieve a fully spin-valley polarized beam for quantum logic applications.
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The issue of a possible tide gauge datum discontinuity at Brest, caused by the bombing of the city in August 1944, is discussed. This issue is very important, as many scientists have used this long record to derive a long-term sea...
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The issue of a possible tide gauge datum discontinuity at Brest, caused by the bombing of the city in August 1944, is discussed. This issue is very important, as many scientists have used this long record to derive a long-term sea level trend estimate for use within global sea level rise studies. A detailed analysis of historical leveling information, and comparison of sea level data between adjacent stations, proved to be worthwhile, even beyond this initial scope of the study: it led to an accurate datum connection between recently rediscovered 18th century sea level data (back to 1711) and those of the present day. The study provides additional evidence that the onset of recent rapid sea level rise most likely took place in the late 19th century, in agreement with the nearby Liverpool sea-level record and with independent results from sediment cores collected in salt marshes located in both hemispheres. Citation: Woppelmann, G., N. Pouvreau, A. Coulomb, B. Simon, and P. L. Woodworth (2008), Tide gauge datum continuity at Brest since 1711: France's longest sea-level record, Geophys. Res. Lett., 35, L22605, doi:10.1029/2008GL035783.
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Nine long and nearly continuous sea level records were chosen from around the world to explore rates of change in sea level for 1904 - 2003. These records were found to capture the variability found in a larger number of stations ...
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Nine long and nearly continuous sea level records were chosen from around the world to explore rates of change in sea level for 1904 - 2003. These records were found to capture the variability found in a larger number of stations over the last half century studied previously. Extending the sea level record back over the entire century suggests that the high variability in the rates of sea level change observed over the past 20 years were not particularly unusual. The rate of sea level change was found to be larger in the early part of last century (2.03 0.35 mm/yr 1904 - 1953), in comparison with the latter part ( 1.45 0.34 mm/yr 1954 - 2003). The highest decadal rate of rise occurred in the decade centred on 1980 (5.31 mm/yr) with the lowest rate of rise occurring in the decade centred on 1964 ( - 1.49 mm/yr). Over the entire century the mean rate of change was 1.74 0.16 mm/yr.
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Hourly time series at seven locations throughout the southern Gulf of Mexico were used to calculate the trend and the inter-annual sea level. The sea level series from January 1966 to December 1976 were filtered using a Lanczos lo...
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Hourly time series at seven locations throughout the southern Gulf of Mexico were used to calculate the trend and the inter-annual sea level. The sea level series from January 1966 to December 1976 were filtered using a Lanczos low pass filter to remove oscillations with periods smaller than one year. The results revealed a sea level increment of about 1.4 mm yr(-1) from 1966 to 1976 in the southern Gulf of Mexico. The monthly sea level variability obtained after the trends were removed, presented a sea level setup during winter and a sea level depression in summer attributed to seasonal wind conditions. The horizontal representation of averaged sea level in the southern Gulf of Mexico presented a saddle critical point. The associated sea level slope indicated water accumulation at Ciudad Madero in the western side of the gulf and Coatzacoalcos in the southernmost station, and sea level depressions at Tuxpan and Progreso in the southwestern and southeastern side of the gulf, respectively. Nevertheless, one of the most intriguing result is the presence of a Kelvin wave with a two mode oscillation axis that goes from Progreso to Tuxpan.
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Middle latitudes of the northern and southern hemispheres of the western Pacific are the sensitive areas for the climatic change. We reconstruct the variation in primary productivity to evaluate the shift of the transition zone be...
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Middle latitudes of the northern and southern hemispheres of the western Pacific are the sensitive areas for the climatic change. We reconstruct the variation in primary productivity to evaluate the shift of the transition zone between the central water mass and cold water in the both hemispheres. In cores S2612 and LH3166, which are located around boreal and austral 35 degree, the mean C_Organic/N atomic ratios are 7.8 and 7.2, respectively.
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[1] Observations of sea level at Port Arthur, Tasmania, southeastern Australia, based on a two-year record made in 1841 - 1842, a three-year record made in 1999 - 2002, and intermediate observations made in 1875 - 1905, 1888 and 1...
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[1] Observations of sea level at Port Arthur, Tasmania, southeastern Australia, based on a two-year record made in 1841 - 1842, a three-year record made in 1999 - 2002, and intermediate observations made in 1875 - 1905, 1888 and 1972, indicate an average rate of sea level rise, relative to the land, of 0.8 +/- 0.2 mm/year over the period 1841 to 2002. When combined with estimates of land uplift, this yields an estimate of average sea level rise due to an increase in the volume of the oceans of 1.0 +/- 0.3 mm/year, over the same period. These results are at the lower end of the recent estimate by the Intergovernmental Panel on Climate Change of global average rise for the 20th century. They provide an important contribution to our knowledge of past sea level rise in a region ( the Southern Hemisphere) where there is a dearth of other such data. [References: 20]
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In this research an attempt has been made in order to determine the efficiency of different types of structural systems at different heights up to 30 stories (300 feet). The investigation has been carried out on three types of lat...
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In this research an attempt has been made in order to determine the efficiency of different types of structural systems at different heights up to 30 stories (300 feet). The investigation has been carried out on three types of lateral load resisting systems i.e. moment resisting frame, building frame system and outrigger braced frame system for seismic zone 2B as per UBC 1997 considering dead, live, seismic, wind load and their combinations. It was found that up to a 5 story building (50 feet) moment resisting frame was found more cost efficient as moment resisting frame was found stiff enough to resist lateral load and addition of shear wall was not required for further increase in stiffness. From 6 story building up to 20 story building (200 feet) building frame system was found more cost efficient and from 21 story building and beyond outrigger braced frame system was found more cost efficient. Accordingly, from one to five story buildings were categorized as low rise, from six to nineteen story buildings as medium rise and from twenty stories onwards as high rise buildings.
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Shatsky Rise in the Northwest Pacific is the best example so far of an oceanic plateau with two potential hotspot tracks emanating from it: the linear Papanin volcanic ridge and the seamounts comprising Ojin Rise. Arguably, these ...
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Shatsky Rise in the Northwest Pacific is the best example so far of an oceanic plateau with two potential hotspot tracks emanating from it: the linear Papanin volcanic ridge and the seamounts comprising Ojin Rise. Arguably, these hotspot tracks also project toward the direction of Hess Rise, located similar to 1200 km away, leading to speculations that the two plateaus are connected. Dredging was conducted on the massifs and seamounts around Shatsky Rise in an effort to understand the relationship between these plateaus and associated seamounts. Here, we present new Ar-40/Ar-39 ages and trace element and Nd, Pb, and Hf isotopic data for the recovered dredged rocks and new trace elements and isotopic data for a few drill core samples from Hess Rise. Chemically, the samples can be subdivided into plateau basalt-like tholeiites and trachytic to alkalic ocean-island basalt compositions, indicating at least two types of volcanic activity. Tholeiites from the northern Hess Rise (DSDP Site 464) and the trachytes from Toronto Ridge on Shatsky's TAMU massif have isotopic compositions that overlap with those of the drilled Shatsky Rise plateau basalts, suggesting that both Rises formed from the same mantle source. In contrast, trachytes from the southern Hess Rise (DSDP Site 465A) have more radiogenic Pb isotopic ratios that are shifted toward a high time-integrated U/Pb (HIMU-type mantle) composition. The compositions of the dredged seamount samples show two trends relative to Shatsky Rise data: one toward lower Nd-143/Nd-144 but similar Pb-206/Pb-204 ratios, the other toward similar Nd-143/Nd-144 but more radiogenic Pb-206/Pb-204 ratios. These trends can be attributed to lower degrees of melting either from lower mantle material during hotspot-related transition to plume tail or from less refractory shallow mantle components tapped during intermittent deformation-related volcanism induced by local tectonic extension between and after the main volcanic-edifice building episodes on Shatsky Rise. The ocean-island-basalt-like chemistry and isotopic composition of the Shatsky and Hess rise seamounts contrast with those formed by purely deformation-related shallow mantle-derived volcanism, favoring the role of a long-lived mantle anomaly in their origin. Finally, new Ar-40/Ar-39 evidence indicates that Shatsky Rise edifices may have been formed in multiple-stages and over a longer duration than previously believed. (C) 2016 Elsevier Ltd. All rights reserved.
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