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We invert ISC PcP and PKP absolute and differential traveltimes in an attempt to infer the long-wavelength topography of the core-mantle boundary (CMB). The data selection and processing methods are described and evaluated. These travel-time data are very noisy and the geographic distribution of the data is highly non-uniform, inhibiting reliable inference of CMB topography. Spatial averaging enhances the coherent component of the residual variance (related to heterogeneity), however, the random component of the variance is much larger than the coherent component. We show that for PcP data the coherent signal due to mantle heterogeneity overshadows that arising from the CMB, and that the effects of mantle heterogeneity are mapped into our inferred CMB solutions. The PcP data are not correlated across the spatial averaging bins and seem to have a strong bias due to small-scale structure and/or noise. The non-uniform geographic sampling of the data plays a role in the mapping of mantle heterogeneity onto the CMB. Spatial patterns of CMB models inferred from different phases do not agree. Amplitudes of seismically inferred CMB undulations vary greatly. The sensitivity of inferred CMB models to the processing, spatial averaging procedure, and inversion techniques are investigated. Topographic amplitudes increase strongly with increasing input residual variance. The power spectrum of inferred topography indicates that there are unmodelled heterogeneities that must be described with spherical harmonics of degree 6 and higher. Based on this work, we conclude that reliable inference of long-wavelength CMB topography is not likely with the current ISC data set or with a spherical harmonic expansion truncated to degree and order 6. 相似文献
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J. Rodgers 《International Journal of Earth Sciences》1982,71(2):441-443
In the late 1830's and 1840's, the brothersWilliam andHenry Rogers (1843) explored the extraordinarily regular fold system of the Central Appalachian Valley and Ridge Province, the first such system to be accurately described, and showed that all the folds formed together within a single, tangential field of force. Their (hand-colored) cross sections, made with no vertical exaggeration and published in 1844, are of astonishing accuracy even today.William Rogers (1884) discovered several of the parallel thrust faults farther south in the province, although he interpreted them as steep upthrusts.Henry Rogers (1845) showed that slaty cleavage has the same trend as the associated folds and formed in the same force field, and he correctly interpreted an angular discordance between Ordovician and Silurian strata as evidence for an earlier period of deformation, although the importance of such precocious orogenies was not then understood. Somewhat later,James Hall (1859, 1883) recognized that the belt of folding was prefigured by a belt of exceptionally thick sediments, andJames D. Dana (1873) called the latter geosynclinal, attributing both belts to lateral compression caused by contraction of the Earth's crust over a cooling and shrinking interior.Late in the 19th century, studies in the Southern Appalachians produced several additional concepts, roughly contemporaneous with similar ideas in Europe: erosion thrusts (Hayes, 1891), underthrusting (Smith, 1893), competence and incompetence of deforming strata, and prefiguring of folds during sedimentation (Willis, 1893). In our own century, John L. Rich's article on the Pine Mountain (Cumberland) thrust sheet established the principle that much folding results from the stepping (ramping) of thrust faults from one incompetent layer to another.
Zusammenfassung In den dreißiger und vierziger Jahren des neunzehnten Jahrhunderts erkundeten die BrüderWilliam undHenry Rogers (1843) das außerordentlich regelmäßige Faltensystem der Valley and Ridge Provinz der Zentralappalachen. Es war das erste genau beschriebene System dieser Art. Die Brüder Rogers zeigten, daß alle Falten zusammen in einem einzigen tangentialen Kraftfeld erzeugt worden waren. Ihre nicht überhöhten, handgefärbten Profile, 1844 veröffentlicht, sind selbst heute noch von erstaunlicher Genauigkeit.William Rogers (1884) entdeckte mehrere der parallelen Überschiebungen weiter südlich in der Provinz, deutete sie jedoch als steile Aufschiebungen.Henry Rogers (1845) zeigte, daß die Schieferung das gleiche Streichen, wie die verwandten Falten hat, und in dem gleichen Kraftfeld entstanden sind. Richtig deutete er eine Winkeldiskordanz zwischen ordovizischen und silurischen Lagen als Zeugen einer früheren Deformationsepisode, obwohl die Bedeutung solcher vorlaufenden Gebirgsbildungen damals noch nicht erkannt war. Etwas später erkannteJames Hall (1859, 1883), daß der Faltengürtel von einer Zone außerordentlich mächtiger Sedimentablagerungen vorgezeichnet war; J. D.Dana (1873) nannte diese Geosynklinale, indem er beide lateraler Kompression zuschrieb, verursacht durch Kontraktion der Erdkruste über einem abkühlenden und schrumpfenden Erdinneren.Im späten 19. Jahrhundert zeugten Forschungen in den Südappalachen mehrere weitere Konzepte, ungefähr gleichzeitig mit ähnlichen Ideen in Europa: Reliefüberschiebungen (Hayes, 1891); Unterschiebung (Smith, 1893); Kompetenz und Inkompetenz bei der Deformation von Schichtgesteinen; und Vorzeichnung von Falten während der Sedimentation (Willis, 1893). In unserem Jahrhundert hat J. L. Rich in seiner Arbeit über die Pine Mountain (Cumberland) Überschiebungsdecke den Grundsatz festgelegt, daß ein großer Anteil der Faltung durch stufenartiges Aufsteigen (ramping) von Überschiebungen von einer inkompetenten Lage zur nächsten entsteht.
Résumé Dans les années 1830 á 1850, les frèresHenry etWilliam Rogers (1843) explorèrent le système des plis si réguliers de la province des Vallées et Crêtes dans les Appalaches centrales, le premier système de tels plis qui ait été exactement décrit, et ils montrèrent que tous ces plis se sont formés dans un seul champ de force. Leurs coupes (coloriées à la main), publiées en 1844 sans exagération verticale, possèdent une exactitude étonnante encore de nos jours.William Rogers (1884) découvrit quelques-uns des chevauchements parallèles, plus au sud dans la province, bien qu'il les interprétât comme des failles inverses de soulèvement.Henry Rogers (1845) reconnut que la schistosité (ardoisière) montre la même direction que les plis associés, ayant été formée dans le même champ de forces, et il interpréta correctement une discordance angulaire entre des strates ordoviciennes et siluriennes comme indiquant une période d'orogenèse antérieure, quoique la signification de telles orogenèses précoces ne fût pas comprise à cette époque. Un peu plus tard,James Hall (1859, 1883) reconnut que la zone de plissement appalachienne avait été préfigurée par une zone de sédimentation particulièrement épaisse, et D.Dana (1873) dénomma cette dernière zone «géosynclinale». Il attribua la formation des deux zones à la compression latérale due á la contraction de l'écorce terrestre au-dessus de l'intérieur en voie de refroidissement et de rétrécissement.Vers la fin du 19e siècle, des études dans les Appalaches méridionales aboutirent a des conceptions additionelles, sensiblement au moment de la découverte d'idées semblables en Europe: chevauchements épiglyptiques, (Hayes, 1981), sous-charriages (Smith, 1893), compétence relative des strates en cours de déformation, et anticipation des plis pendant la sédimentation (Willis, 1893). Dans notre siècle, les travaux de L.Rich sur le chevauchement de Pine Mountain (Cumberland) établirent le principe que beaucoup de plis résultent de la montée en rampe des surfaces de chevauchement d'un horizon peu compétent à un autre.
William Henry Rogers (1843) 30- 40- Vallea Ridge . . , , , 1844 , . William Rogers (1884) , . Henry Rogers (1845) , , . , . James Hall (1859, 1883) , ; J. D. Dane (1873) , , . 19- , : (Hayes, 1891); (Smith, 1893); , , , , (Willis, 1893). J. L. Rich , , , .相似文献
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Arthur Rodgers Hrvoje Tkalcic David McCallen Shawn Larsen Catherine Snelson 《Pure and Applied Geophysics》2006,163(1):55-80
We report site response in Las Vegas Valley (LVV) from historical recordings of Nevada Test Site (NTS) nuclear explosions
and earthquake recordings from permanent and temporary seismic stations. Our data set significantly improves the spatial coverage
of LVV over previous studies, especially in the northern, deeper parts of the basin. Site response at stations in LVV was
measured for frequencies in the range 0.2–5.0 Hz using Standard Spectral Ratios (SSR) and Horizontal-Vertical Spectral Ratios
(HVR). For the SSR measurements we used a reference site (approximately NEHRP B ``rock' classification) located on Frenchman
Mountain outside the basin. Site response at sedimentary sites is variable in LVV with average amplifications approaching
a factor of 10 at some frequencies. We observed peaks in the site response curves at frequencies clustered near 0.6, 1.2 and
2.0 Hz, with some sites showing additional lower amplitude peaks at higher frequencies. The spatial pattern of site response
is strongly correlated with the reported depth to basement for frequencies between 0.2 and 3.0 Hz, although the frequency
of peak amplification does not show a similar correlation. For a few sites where we have geotechnical shear velocities, the
amplification shows a correlation with the average upper 30-meter shear velocities, V30. We performed two-dimensional finite difference simulations and reproduced the observed peak site amplifications at 0.6 and
1.2 Hz with a low velocity near-surface layer with shear velocities 600–750 m/s and a thickness of 100–200 m. These modeling
results indicate that the amplitude and frequencies of site response peaks in LVV are strongly controlled by shallow velocity
structure. 相似文献
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Abstract Aquifers occur in basalt deposits infilling valleys in the Western Springs catchment of Auckland City, and they discharge into small streams incised along the edges of major lava flows. Total run‐off from the area is >0.261 m3·s?1. Analyses by standard methods of twelve subsurface and surface waters show that flowing groundwaters have a low level of pollution (dissolved oxygen x = 7.6 mg·l?1, abuminoid nitrogen x = 0.038 mg·l?1, and total solids x = 188 mg·l?1). Surface waters and stagnant groundwater have high, but varying levels of biological activity. Although much of the dissolved solid content of all the waters (e.g., Ca2+, Mg2+, Na+, K+, SiO2) is consistent with the chemistry of the rocks of the catchment, particularly the glassy volcanic tuffs, for surface waters various sources of pollution also make significant contributions (e.g., leaking sewers, sewage overflows, combustion of fossil fuels, fertilisers, zoo animals). Apart from its iron level, the moderate volume (～.0.13 m3·s?1) of flowing groundwater is of suitable quality for domestic, industrial and irrigation needs. 相似文献
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Geochemically based hydrograph separation techniques were used in a preliminary assessment to infer how runoff processes change with landscape characteristics and spatial scale (1–233 km2) within a mesoscale catchment in upland Scotland. A two‐component end‐member mixing analysis (EMMA) used Gran alkalinity as an assumed conservative tracer. Analysis indicated that, at all scales investigated, acidic overland flow and shallow subsurface storm flows from the peaty soils covering the catchment headwaters dominated storm runoff generation. The estimated groundwater contribution to annual runoff varied from 30% in the smallest (ca 1 km2) peat‐dominated headwater catchment with limited groundwater storage, to >60% in larger catchments (>30 km2) with greater coverage of more freely draining soils and more extensive aquifers in alluvium and other drift. This simple approach offers a useful, integrated conceptualization of the hydrological functioning in a mesoscale catchment, which can be tested and further refined by focused modelling and process‐based research. However, even as it stands, the simple conceptualization of system behaviour will have significant utility as a tool for communicating hydrological issues in a range of planning and management decisions. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Rengin Gök Hanan Mahdi Haydar Al-Shukri Arthur J. Rodgers 《Geophysical Journal International》2008,172(3):1179-1187
We report the crustal structure for two locations in Iraq estimated by joint inversion of P -wave receiver functions (RFs) and surface (Rayleigh) wave group velocity dispersion. RFs were computed from teleseismic recordings at two temporary broad-band seismic stations located in Mosul (MSL) in the Zagros Fold Belt and Baghdad (BHD) in the Mesopotamian Foredeep. Group velocity dispersion curves at the sites were derived from continental-scale tomography. The inversion results show that the crustal thicknesses are 39 km at MSL and 43 km at BHD. We observe a strong Ps Moho at BHD consistent with a sharp Moho discontinuity. However, at MSL we observe a weak Ps Moho suggesting a transitional Moho where crustal thickening is likely to be occurring in the deep crust. Both sites reveal low velocity surface layers consistent with sedimentary thickness of about 3 km at station MSL and 7 km at BHD and agreeing well with the previous reports. Ignoring the sediments, the crystalline crustal velocities and thicknesses are remarkably similar at both stations. The similarity of crustal structure suggests that the crust of the northeastern proto-Arabian Platform was uniform before subsidence and deposition of the sediments in the Cenozoic. If crystalline crustal structure is uniform across the northern Arabian Platform then crustal thickness variations in the Zagros Fold Belt and Thrust Zone should reveal the history of deformation and crustal shortening in the Arabian–Eurasian collision zone and not reflect pre-existing crustal thickness variations in the Arabian Plate. 相似文献
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K. J. Mulligan J. G. Chase J. B. Mander G. W. Rodgers R. B. Elliott R. Franco‐Anaya A. J. Carr 《地震工程与结构动力学》2009,38(4):517-536
The seismic performance of a test structure fitted with semi‐active resetable devices is experimentally investigated. Shaking table tests are conducted on a ?th scale four‐storey building using 27 earthquake records at different intensity scalings. Different resetable device control laws result in unique hysteretic responses from the devices and thus the structure. This device adaptability enables manipulation or sculpting of the overall hysteresis response of the structure to address specific structural cases and types. The response metrics are presented as maximum 3rd floor acceleration and displacement, and the total base shear. The devices reduce all the response metrics compared with the uncontrolled case and a fail‐safe surrogate. Cumulative probability functions allow comparison between different control laws and additionally allow tradeoffs in design to be rapidly assessed. Ease of changing the control law in real‐time during an earthquake record further improves the adaptability of the system to obtain the optimum device response for the input motion and structural type. The findings are an important step to realizing full‐scale structural control with customized semi‐active hysteretic behaviour using these novel resetable device designs. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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D.L. Tucker S. Kent M.W. Richmond J. Annis J.A. Smith S.S. Allam C.T. Rodgers J.L. Stute J.K. Adelman‐McCarthy J. Brinkmann M. Doi D. Finkbeiner M. Fukugita J. Goldston B. Greenway J.E. Gunn J.S. Hendry D.W. Hogg S.‐I. Ichikawa
. Ivezi&#x; G.R. Knapp H. Lampeitl B.C. Lee H. Lin T.A. McKay A. Merrelli J.A. Munn E.H. Neilsen H.J. Newberg G.T. Richards D.J. Schlegel C. Stoughton A. Uomoto B. Yanny 《Astronomische Nachrichten》2006,327(9):821-843
The photometric calibration of the Sloan Digital Sky Survey (SDSS) is a multi‐step process which involves data from three different telescopes: the 1.0‐m telescope at the US Naval Observatory (USNO), Flagstaff Station, Arizona (which was used to establish the SDSS standard star network); the SDSS 0.5‐m Photometric Telescope (PT) at the Apache Point Observatory (APO), NewMexico (which calculates nightly extinctions and calibrates secondary patch transfer fields); and the SDSS 2.5‐m telescope at APO (which obtains the imaging data for the SDSS proper). In this paper, we describe the Monitor Telescope Pipeline, MTPIPE, the software pipeline used in processing the data from the single‐CCD telescopes used in the photometric calibration of the SDSS (i.e., the USNO 1.0‐m and the PT). We also describe transformation equations that convert photometry on the USNO‐1.0m u ′g ′r ′i ′z ′ system to photometry the SDSS 2.5m ugriz system and the results of various validation tests of the MTPIPE software. Further, we discuss the semi‐automated PT factory, which runs MTPIPE in the day‐to‐day standard SDSS operations at Fermilab. Finally, we discuss the use of MTPIPE in current SDSS‐related projects, including the Southern u ′g ′r ′i ′z ′ Standard Star project, the u ′g ′r ′i ′z ′ Open Star Clusters project, and the SDSS extension (SDSS‐II). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献