A reassessment of dynamic characteristics of the Quincy Bayview Bridge using output‐only identification techniques

A reassessment of the dynamic characteristics of the 542 m cable‐stayed Bayview Bridge in Quincy, Illinois, is presented using a newly developed output‐only system identification technique. The technique is applied to an extensive set of ambient vibration response data acquired from the bridge in 1987. Vertical, torsional and transverse modal frequencies of the deck are identified, and uncertainty in damping values are estimated using an automated procedure on several redundant measurements at four locations. Important practical implementation issues associated with the implementation of the procedure and selection of algorithm design parameters for stochastic subspace identification techniques are discussed. An overall mean and standard deviation of damping of 1.0±0.8% is estimated considering all identified vertical, torsional and transverse modes in the 0–2 Hz band. The mean damping for the fundamental vertical mode (0.37 Hz) is identified as 1.4±0.5%, and for the first coupled torsion–transverse mode (0.56 Hz) is identified as 1.1±0.8%. Variability in the damping estimates is shown to decrease as estimated modal RMS acceleration levels increase. Standard deviations on estimated damping range from 0.05% to 2%. The results are shown to be a substantial improvement in the evaluation of damping compared to earlier spectral analysis conducted on the same data set. Copyright © 2005 John Wiley & Sons, Ltd.     

Conrad Deep, Northern Red Sea: Development of an early stage ocean deep within the axial depression

The northern Red Sea represents a continental rift in its final stage and close to the following stage of seafloor spreading. Ocean deeps within the evaporites of the northern Red Sea seem to accompany this process and are thought to be surface expressions of first seafloor spreading cells. In 1999 during R/V Meteor cruise M44/3 a dense multichannel seismic and hydroacoustic survey was conducted in order to investigate the initial formation process of the Conrad Deep, a young northern Red Sea deep. Three seismic units were differentiated in the uppermost part of the Miocene evaporites and the Plio-Quaternary sediments. A weakness zone within the evaporites, oblique to the main extension direction of the Red Sea, led to a transtension process within the evaporites that opened the deep. Its formation is directly related to the emplacement of magmatic bodies in its vicinity and the focusing of the Red Sea extension to the axial depression. The Conrad Deep is an intra-evaporite basin that cannot be regarded as surficial expression of a basement structure as the low shear strength of the evaporites decouple the sediments from the basement. However, its position and shape in combination with the accompanying geophysical anomalies point to a strong correlation with the Red Sea rifting process.     

The Devonian–Lower Carboniferous succession in Northwest Peninsular Malaysia

A new stratigraphic nomenclature is proposed for the approximately 600 m thick, mainly clastic transitional sequence between the underlying Mempelam Limestone and overlying Kubang Pasu/Singa Formation in northwest Peninsular Malaysia. This sequence represents shallow marine deposits of the continental margin of the Sibumasu Terrane during the Middle Palaeozoic (Devonian–Carboniferous). It is separated into several formations. The Timah Tasoh Formation is an approximately 76 m sequence consisting of 40 m of laminated tentaculitid shales at the base, containing Monograptus yukonensis Jackson and Lenz and Nowakia (Turkestanella) acuaria Alberti, giving an Early Devonian (Pragian–Emsian) age, and about 36 m of rhythmically interbedded, light coloured argillo-arenites. The Chepor Formation is about 90 m thick and consists mainly of thick red mudstone interbedded with sandstone beds, of Middle to Late Devonian age. A new limestone unit is recognized and named the Sanai Limestone, which contains conodonts of Famennian age. The Binjal Formation consists of red and white mudstone interbedded with sandstone beds showing Bouma sequences. The Telaga Jatoh Formation is 9 m thick and consists mainly of radiolarian chert. The Wang Kelian Formation is composed of thick red mudstone beds interbedded with silty sandstone, and contain fossils indicative of an Early Carboniferous (Visean) age. The succession was deposited on the outer shelf, with depositional environments vertically fluctuating from prodelta to basinal marine. The Devonian–Carboniferous boundary is exposed at Hutan Aji and Kampung Guar Jentik, and indicates a major regressive event during the latest Devonian.     

Stability and P–V–T equation of state of KAlSi3O8-hollandite determined by in situ X-ray observations and implications for dynamics of subducted continental crust material

In situ X-ray diffraction measurements of KAlSi₃O₈-hollandite (K-hollandite) were performed at pressures of 15–27 GPa and temperatures of 300–1,800 K using a Kawai-type apparatus. Unit-cell volumes obtained at various pressure and temperature conditions in a series of measurements were fitted to the high-temperature Birch-Murnaghan equation of state and a complete set of thermoelastic parameters was obtained with an assumed K′_300,0=4. The determined parameters are V _300,0=237.6(2) Å³, K _300,0=183(3) GPa, (?K _T,0/?T) _P =?0.033(2) GPa K^?1, a ₀=3.32(5)×10^?5 K^?1, and b ₀=1.09(1)×10^?8 K^?2, where a ₀ and b ₀ are coefficients describing the zero-pressure thermal expansion: α _T,0 = a ₀ + b ₀ T. We observed broadening and splitting of diffraction peaks of K-hollandite at pressures of 20–23 GPa and temperatures of 300–1,000 K. We attribute this to the phase transitions from hollandite to hollandite II that is an unquenchable high-pressure phase recently found. We determined the phase boundary to be P (GPa)=16.6 + 0.007 T (K). Using the equation of state parameters of K-hollandite determined in the present study, we calculated a density profile of a hypothetical continental crust (HCC), which consists only of K-hollandite, majorite garnet, and stishovite with 1:1:1 ratio in volume. Density of HCC is higher than the surrounding mantle by about 0.2 g cm^?3 in the mantle transition zone while this relation is reversed below 660-km depth and HCC becomes less dense than the surrounding mantle by about 0.15 g cm^?3 in the uppermost lower mantle. Thus the 660-km seismic discontinuity can be a barrier to prevent the transportation of subducted continental crust materials to the lower mantle and the subducted continental crust may reside at the bottom of the mantle transition zone.     

Synsedimentary faults and amalgamated unconformities: Insights from 3D-seismic and core analysis of the Lower Triassic Middle Buntsandstein, Ems Trough, north-western Germany

The Late Permian/Early Triassic succession of the Central European Basin (CEB) was repeatedly affected by the tectonic pulses associated with the earliest phases of Tethyan and Arctic–North Atlantic rifting. Effects of the differential tectonic subsidence are particularly well recorded by unconformities, which form widespread sequence boundaries. Such unconformities are most obvious in areas occupied by fault-controlled intra-basinal highs (swells). In that areas, stratigraphic loss may comprise entire Lower and Middle Buntsandstein formations and in places remnant Middle Buntsandstein successions directly rest on Permian strata. Analysis of 3D-seismic data and well logs combined with high-resolution sedimentological logging of drillcores at the western margin of the Ems Trough (NW Germany) reveals details of synsedimentary tectonic control on sequence development. Early Triassic extensional faulting of basement blocks provided stepwise addition of accommodation space for continental sequences by growth faulting along north–south oriented fault zones blocks on the flanks of the East Netherlands High. This process is most evident during the development of the Hardegsen Unconformity, which is characterised by an amalgamation of succeeding unconformity surfaces in areas of structurally controlled intrabasinal highs.     

Cenozoic Magmatism of the North-Eastern Eurasian Margin: The Role of Lithosphere Versus Asthenosphere

Sikhote-Alin and Sakhalin are located in the Russian Far Eastflank of the northernmost part of the Sea of Japan. Magmatismin this region preceded, was concurrent with, and continuedafter the extension and sea-floor spreading (25–18 Ma)that formed the Sea of Japan. Among the Sikhote-Alin and Sakhalinvolcanic suites, Eocene–Oligocene (55–24 Ma) lavasare characterized by greater large ion lithophile element andrare earth element enrichments compared with Early–Mid-Miocene(23–15 Ma) tholeiites, and also show a depletion in highfield strength elements (HFSE). The geochemical characteristicsof the Eocene–Oligocene and Early–Mid-Miocene basaltsare consistent with migration of the locus of magma generationbeneath the Sikhote-Alin and Sakhalin areas from subduction-modifiedlithospheric mantle into mid-ocean ridge basalt (MORB)-sourceasthenosphere as spreading in the Sea of Japan progressed. Mid-Miocene–Pliocene(14–5 Ma) lavas, erupted following the opening of theSea of Japan, include alkaline and sub-alkaline basalts withwide ranges in trace-element abundances, varying between twodistinct end-members: (1) volumetrically minor alkaline basaltswith Zr–Nb and Sr–Nb–Pb isotope compositionssimilar to asthenosphere-derived, intra-plate–hotspotbasalts from eastern China; (2) more abundant, lithosphere-derived,low-alkali tholeiites depleted in HFSE. The similarity of isotopicsignatures coupled with systematically different rare earthelement (REE) abundances in the Mid-Miocene–Pliocene andChinese basalts are best modeled by similar extents of meltingof spinel lherzolite and garnet lherzolite, respectively. TheMid-Miocene–Pliocene alkali basalts were generated bysmall degrees of partial melting of hot asthenosphere beneatha thin lithospheric lid; the thin lithospheric mantle beneaththe Sikhote-Alin and Sakhalin region resulted from heating andextension associated with the opening of the Sea of Japan. KEY WORDS: north-eastern Eurasian margin; Sikhote-Alin–Sakhalin; Japan Sea opening; subcontinental lithosphere; asthenosphere     

德国鲁尔区工业地域变迁的模式与启示

本文在分析鲁尔工业区的历史演变过程及其经济转型引起的失业,污染,停产,人口流失,社会形象下降等一系列问题的基础上,总结了鲁尔工业区改造过程中所采取的产业政策,政府导向,财政补贴和发展工业旅游景观的措施,介绍了埃姆什工业改造样板的发展。通过对鲁尔工业区地域结构转型模式,探讨了这一模式对我国东北老工业基地改造的启示。     

The Impact of U.S. Government Antiterrorism Policies on Canada‐U.S. Cross‐Border Commerce: An Exploratory Study from Western New York and Southern Ontario

This article examines the extant and potential impact of U.S. antiterrorism policies on Canada‐U.S. cross‐border commerce. Particular attention is focused on the cross‐border trade that takes place between southern Ontario (Canada) and western New York (United States). Evidence from a survey of Canadian and U.S. exporters suggests that U.S. antiterrorism measures have inflated the business costs of exporters on both sides of the border. These measures have also created shipment delays that ultimately imply lost revenues for producers, as well as higher prices for consumers. Security‐related initiatives motivated by a genuine concern for the well‐being of U.S. citizens may nevertheless act as nontariff barriers to bilateral trade. We argue that a potential long‐run consequence of these additional costs is trade diversion. The article concludes with a brief discussion of the implications of the empirical findings for the geography of Canada‐U.S. bilateral trade.     

综合电法在祁连山山前缺水区寻找地下水的应用

应用电测深、激电测深和瞬变电磁测深方法,结合区域水文地质条件,在被前人判定为贫水或无水区的河西走廊祁连山山前缺水区开展了综合电法勘查找水工作,分别发现了分布面积广的第四系大厚度粘土层深部和第三系泥岩深部存在高阻含水体。经20余眼水文地质勘探孔验证,单井涌水量大于2000m³/d,矿化度小于1.0g/L,布井成功率达95%以上。不但彻底解决了这一地区人饮水源的问题,而且为今后类似地区的找水工作积累了经验,具有显著的社会效益。     

Petrogenesis and tectonic setting of the peralkaline Pine Canyon caldera, Trans-Pecos Texas, USA

The Pine Canyon caldera is a small (6–7 km diameter) ash-flow caldera that erupted peralkaline quartz trachyte, rhyolite, and high-silica rhyolite lavas and ash-flow tuffs about 33–32 Ma. The Pine Canyon caldera is located in Big Bend National Park, Texas, USA, in the southern part of the Trans-Pecos Magmatic Province (TPMP). The eruptive products of the Pine Canyon caldera are assigned to the South Rim Formation, which represents the silicic end member of a bimodal suite (with a “Daly Gap” between 57 and 62 wt.% SiO₂); the mafic end member consists primarily of alkali basalt to mugearite lavas of the 34–30 Ma Bee Mountain Basalt. Approximately 60–70% crystallization of plagioclase, clinopyroxene, olivine, magnetite, and apatite from alkali basalt coupled with assimilation of shale wall rock (M_a/M_c = 0.3–0.4) produced the quartz trachyte magma. Variation within the quartz trachyte–rhyolite suite was the result of 70% fractional crystallization of an assemblage dominated by alkali feldspar with subordinate clinopyroxene, fayalite, ilmenite, and apatite. High-silica rhyolite is not cogenetic with the quartz trachyte–rhyolite suite, and can be best explained as the result of  5% partial melting of a mafic granulite in the deep crust under the fluxing influence of fluorine. Variation within the high-silica rhyolite is most likely due to fractional crystallization of alkali feldspar, quartz, magnetite, biotite, and monazite. Lavas and tuffs of the South Rim Formation form A-type rhyolite suites, and are broadly similar to rock series described in anorogenic settings both in terms of petrology and petrogenesis. The Pine Canyon caldera is interpreted to have developed in a post-orogenic tectonic setting, or an early stage of continental rifting, and represents the earliest evidence for continental extension in the TPMP.