An application of disjunctive kriging for earthquake ground motion estimation     

James R. Carr  Eddy D. Deng  Charles E. Glass 《Mathematical Geology》1986,18(2):197-213

For earthquake ground motion studies, the actual ground motion distribution should be reproduced as accurately as possible. For optimal estimation of ground motion, kriging has been shown to provide accurate estimates. Although kriging is accurate for this application, some estimates it provides are underestimates. This has dire consequences for subsequent design for earthquake resistance. Kriging does not provide enough information to allow an analysis of each estimate for underestimation. For such an application, disjunctive kriging is better applied. This advanced technique quantifies the probability that an estimate equals or exceeds particular levels of ground motion. Furthermore, disjunctive kriging can provide improved estimation accuracy when applied for local estimation of ground motion.  相似文献   

Observation of a possible neutral sheet in the corona   总被引：2，自引：0，他引：2  

John A. Eddy 《Solar physics》1973,30(2):385-394

A linear coronal ray, centered on a large helmet, is prominent in white-light photographs taken at the 1922 eclipse. It extends from near the limb to 4 R , has minimum width 9 arc, and persisted for at least 35 min. Examination reveals that the ray marks the cleavage between the domes of a twin-arch streamer which in turn is associated with two large, distinct chromospheric active regions. The ray is interpreted as the edge-on aspect of a coronal neutral sheet which separates areas of presumed opposite magnetic polarity in the two surface regions.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

The βFeOOH to αFe2O3 phase transformation: Structural and magnetic phenomena     

Danny G. Chambaere  Eddy De Grave 《Physics and Chemistry of Minerals》1985,12(3):176-184

It is shown that under ambient atmospheric conditions heating causes the crystal structure of βFeOOH (synthetic akaganeite) to degenerate gradually into a quasi amorphous intermediate state, before the final phase transformation to αFe₂O₃ (hematite) takes place. Using X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Mössbauer Spectroscopy, this amorphization process is monitored and the structural, morphological and magnetic features of the intermediate phase as a function of the isochronal heating temperature are discussed: the crystallites develop macropores on their surface, the adsorption capacity raises up to 10 percent of the initial mass, a third type of Fe³⁺ coordination, having an extremely large quadrupole splitting, is created and the Néel temperature, after an initial decrease, exhibits a sharp increase at higher heating temperatures. The magnetic behaviour of this intermediate phase at low temperatures and in high external fields suggests this antiferromagnet undergoes magnetic phase transitions (metamagnetism and spin flop) at unusually low critical fields.  相似文献   

Climate and the changing sun     

John A. Eddy 《Climatic change》1977,1(2):173-190

Long-term changes in the level of solar activity are found in historical records and in fossil radiocarbon in tree-rings. Typical of these changes are the Maunder Minimum (A.D. 1645–1715), the Spörer Minimum (A.D. 1400–1510), and a Medieval Maximum (c. A.D. 1120–1280). Eighteen such features are identified in the tree-ring radiocarbon record of the past 7500 years and compared with a record of world climate. In every case when long-term solar activity falls, mid-latitude glaciers advance and climate cools; at times of high solar activity glaciers recede and climate warms. We propose that changes in the level of solar activity and in climate may have a common cause: slow changes in the solar constant, of about 1% amplitude.  相似文献   

Book reviews     

H. H. Lamb  John S. Perry  John A. Eddy 《Climatic change》1980,2(4):409-413

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GHR1 Zircon – A New Eocene Natural Reference Material for Microbeam U‐Pb Geochronology and Hf Isotopic Analysis of Zircon     

Michael P. Eddy  Mauricio Ibaez‐Mejia  Seth D. Burgess  Matthew A. Coble  Umberto G. Cordani  Joel DesOrmeau  George E. Gehrels  Xianhua Li  Scott MacLennan  Mark Pecha  Kei Sato  Blair Schoene  Victor A. Valencia  Jeffrey D. Vervoort  Tiantian Wang 《Geostandards and Geoanalytical Research》2019,43(1):113-132

We present multitechnique U‐Pb geochronology and Hf isotopic data from zircon separated from rapakivi biotite granite within the Eocene Golden Horn batholith in Washington, USA. A weighted mean of twenty‐five Th‐corrected ²⁰⁶Pb/²³⁸U zircon dates produced at two independent laboratories using chemical abrasion‐isotope dilution‐thermal ionisation mass spectrometry (CA‐ID‐TIMS) is 48.106 ± 0.023 Ma (2s analytical including tracer uncertainties, MSWD = 1.53) and is our recommended date for GHR1 zircon. Microbeam ²⁰⁶Pb/²³⁸U dates from laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) and secondary ion mass spectrometry (SIMS) laboratories are reproducible and in agreement with the CA‐ID‐TIMS date to within < 1.5%. Solution multi‐collector ICP‐MS (MC‐ICP‐MS) measurements of Hf isotopes from chemically purified aliquots of GHR1 yield a mean ¹⁷⁶Hf/¹⁷⁷Hf of 0.283050 ± 17 (2s, n = 10), corresponding to a εHf₀ of +9.3. Hafnium isotopic measurements from two LA‐ICP‐MS laboratories are in agreement with the solution MC‐ICP‐MS value. The reproducibility of ²⁰⁶Pb/²³⁸U and ¹⁷⁶Hf/¹⁷⁷Hf ratios from GHR1 zircon across a variety of measurement techniques demonstrates their homogeneity in most grains. Additionally, the effectively limitless reserves of GHR1 material from an accessible exposure suggest that GHR1 can provide a useful reference material for U‐Pb geochronology of Cenozoic zircon and Hf isotopic measurements of zircon with radiogenic ¹⁷⁶Hf/¹⁷⁷Hf.  相似文献   

Use of aliphatic hydrocarbons to infer terrestrial organic matter in coastal marine sediments off China     

Liu LY  Wang JZ  Guan YF  Zeng EY 《Marine pollution bulletin》2012,64(9):1940-1946

Sediment samples from the marine systems along the coast of China, covering Yellow Sea, inner shelf of the East China Sea (ECS) and the South China Sea (SCS), were analyzed for n-alkanes and organic carbon. The concentrations of Σn-C(15-35) were 120-1680ngg(-1) dry weight with an average of 560ngg(-1). Short-chain n-alkanes (C(21)) were mainly derived from terrestrial higher plants. Organic carbon deposited into Yellow Sea and Southeast Hainan within the SCS was mainly of terrestrial (13-110%; mean: 58%) and marine (48-110%; mean: 86%) sources, respectively. On the other hand, organic carbon accumulated in the SCS adjacent to the Pearl River Estuary was derived from both terrestrial and marine sources.  相似文献   

Bowhead whales feed on plankton concentrated by estuarine and tidal currents in Academy Bay,Sea of Okhotsk     

Konstantin A. Rogachev  Eddy C. Carmack  Michael G.G. Foreman 《Continental Shelf Research》2008

Academy Bay in the Sea of Okhotsk is an important summertime feeding ground for pelagic-feeding Bowhead whales (Balaena mysticetus) in the western subarctic North Pacific. The present work combines satellite observations with physical (CTD, currents, tides) and biological (zooplankton sampling) measurements. Data obtained aboard the RV Lugovoe in August–September 2003 and July–August 2004 show dense populations of zooplankton (such as copepods Calanus glacialis, Pseudocalanus sp., pteropods Limacina helicina, and chaetognaths Sagitta sp.) that are concentrated by physical mechanisms within this critically important ecosystem. We show that near-bottom, cold water intrusions from the northern Sea of Okhotsk associated with the estuarine circulation advect arctic herbivorous calanoids (Calanus glacialis) and mollusks Limacina helicina into the region.  相似文献   

Understanding mass fluvial erosion along a bank profile: using PEEP technology for quantifying retreat lengths and identifying event timing          下载免费PDF全文

A. N. Thanos Papanicolaou  Christopher G. Wilson  Achilles G. Tsakiris  Tommy E. Sutarto  Fabienne Bertrand  Massimo Rinaldi  Subhasish Dey  Eddy Langendoen 《地球表面变化过程与地形》2017,42(11):1717-1732

This study provides fundamental examination of mass fluvial erosion along a stream bank by identifying event timing, quantifying retreat lengths, and providing ranges of incipient shear stress for hydraulically driven erosion. Mass fluvial erosion is defined here as the detachment of thin soil layers or conglomerates from the bank face under higher hydraulic shear stresses relative to surface fluvial erosion, or the entrainment of individual grains or aggregates under lower hydraulic shear stresses. We explore the relationship between the two regimes in a representative, US Midwestern stream with semi‐cohesive bank soils, namely Clear Creek, IA. Photo‐Electronic Erosion Pins (PEEPs) provide, for the first time, in situ measurements of mass fluvial erosion retreat lengths during a season. The PEEPs were installed at identical locations where surface fluvial erosion measurements exist for identifying the transition point between the two regimes. This transition is postulated to occur when the applied shear stress surpasses a second threshold, namely the critical shear stress for mass fluvial erosion. We hypothesize that the regimes are intricately related and surface fluvial erosion can facilitate mass fluvial erosion. Selective entrainment of unbound/exposed, mostly silt‐sized particles at low shear stresses over sand‐sized sediment can armor the bank surface, limiting the removal of the underlying soil. The armoring here is enhanced by cementation from the presence of optimal levels of sand and clay. Select studies show that fluvial erosion strength can increase several‐fold when appropriate amounts of sand and clay are mixed and cement together. Hence, soil layers or conglomerates are entrained with higher flows. The critical shear stress for mass fluvial erosion was found to be an order of magnitude higher than that of surface fluvial erosion, and proceeded with higher (approximately 2–4 times) erodibility. The results were well represented by a mechanistic detachment model that captures the two regimes. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Length scales and statistical characteristics of outer bank roughness for large elongate meander bends: The influence of bank material properties,floodplain vegetation and flow inundation          下载免费PDF全文

Kory Konsoer  Bruce Rhoads  James Best  Eddy Langendoen  Mick Ursic  Jorge Abad  Marcelo Garcia 《地球表面变化过程与地形》2017,42(13):2024-2037

This article explores the length scales and statistical characteristics of form roughness along the outer banks of two elongate bends on a large meandering river through investigation of topographic variability of the bank face. The analysis also examines how roughness varies over the vertical height of the banks and when the banks are exposed subaerially and inundated during flood stage. Detailed data on the topography of the outer banks were obtained subaerially using terrestrial LiDAR during low flow conditions and subaqueously using multibeam echo sounding (MBES) during near‐bankfull conditions. The contributions of various length scales of topographic irregularity to roughness for subaerial conditions were evaluated for different elevation contours on the bank faces using Hilbert–Huang Transform (HHT) spectral analysis. Statistical characteristics for discrete areas on the bank faces were determined by calculating the root‐mean‐square of normal distances from a triangulated irregular network (TIN) surface. Results of the HHT analysis show that the characteristics of roughness along bank faces composed primarily of non‐cohesive sediment, and eroding into cropland, vary with bank elevation and exhibit a dominant range of roughness length scales (~15–50 m). However, bank faces composed predominantly of cohesive material and carved into a forested floodplain have relatively uniform topographic roughness characteristics over the vertical extent of the bank face and do not exhibit a dominant roughness length scale or range of length scales. Additionally, comparison between local surface roughness for subaerial versus subaqueous conditions shows that roughness decreases considerably when the banks are submerged, most likely because of the removal of vegetation and eradication of small‐scale erosional features in non‐cohesive bank materials by flow along the bank face. Thus, roughness appears to be linked to the hydraulic conditions affecting the bank, at least relative to conditions that develop when banks are exposed subaerially. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献