Ground-Water Problems in the Mesozoic Pax Mountain Fault Zone     

David S. Snipes  Peter R. Manoogian  Michael W. Davis  Laura L. Burnett  Jerry A. Wylie  Steven B. Heaton 《Ground water》1986,24(3):375-381

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REPLY TO the Discussion by James F. Quinlan of Ground Water Tracers     

Stanley N. Davis 《Ground water》1986,24(3):398-399

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Contrasting climatic histories for the Snake River Plain, Idaho, resulting from multiple thermal maxima     

Owen K. Davis  John C. Sheppard  Susan Robertson 《Quaternary Research》1986,26(3)

Ten sites near the Snake River Plain have consistent differences in their climatic histories. Sites at low elevation reflect the “early Holocene xerothermic” of the Pacific Northwest, whereas most climatic chronologies at high elevation indicate maximum warmth or aridity somewhat later, ca. 6000 yr ago. This elevational contrast in climatic histories is duplicated at three sites from the central Snake River Plain. For sites in such close proximity, the different chronologies cannot be explained by changes in atmospheric circulation during the late Quaternary. Rather, the differences are best explained by the autecology of the plants involved and the changing seasonal climate. The seasonal climatic sequence predicted by multiple thermal maxima explains the high- and low-elevation chronologies. During the early Holocene, maximum insolation and intensified summer drought in July forced low-elevation vegetation upward. However, moisture was not a limiting factor at high elevation, where vegetation moved upward in response to increased length of growing season coincident with maximum September insolation 6000 yr ago.  相似文献   

Infrared vibrational spectra of Beta-Phase Mg2SiO4 and Co2SiO4 to Pressures of 27 GPa     

Quentin Williams  Raymond Jeanloz  M. Akaogi 《Physics and Chemistry of Minerals》1986,13(3):141-145

Infrared absorption spectra of the high-pressure polymorphs β-Mg₂SiO₄ and β-Co₂SiO₄ have been measured between 0 and 27 GPa at room temperature. Grüneisen parameters determined for 11 modes of β-Mg₂SiO₄ (frequencies of 300 to 1,050 cm^?1) and 5 modes of β-Co₂SiO₄ (490 to 1,050 cm^?1) range between 0.8 and 1.9. Averaging the mid-infrared spectroscopic data for β-Mg₂SiO₄ yields an average Grüneisen parameter of 1.3 (±0.1), in good agreement with the high-temperature thermodynamic value of 1.35. Similarly, we find a value of 1.05 (±0.2) for the average spectroscopic Grüneisen parameter of β-Co₂SiO₄.  相似文献   

Effects of weathering on site response     

Rob Davis 《地震工程与结构动力学》1995,24(2):301-309

Nearly all studies of site response under seismic excitation employ idealized site models in which uniform layers of homogeneous soils are separated by perfect interfaces. The impedance mismatch at each interface gives rise to wave reflections which strongly affect the calculated free surface response. In reality, these perfect interfaces may often not exist. Instead, a zone in which materials from both above and below are mingled may form a blurred interface between layers. This article examines the effects of such weathered zones. The zone is modelled by a linearly varying shear modulus so that no abrupt impedance change occurs. Significant differences in response of weathered and unweathered profiles are found.  相似文献   

An optimised method for calculating the O+-O collision parameter from aeronomical measurements     

C. J. Davis  A. D. Farmer  A. Aruliah 《Annales Geophysicae》1995,13(5):541-550

A study has been made of the interaction between the thermosphere and the ionosphere at high latitudes, with particular regard to the value of the O⁺-O collision parameter. The European incoherent scatter radar (EISCAT) was used to make tristatic measurements of plasma parameters at F-region altitudes while simultaneous measurements of the neutral wind were made by a Fabry-Perot interferometer (FPI). The radar data were used to derive the meridional neutral winds in a way similar to that used by previous authors. The accuracy of this technique at high latitudes is reduced by the dynamic nature of the auroral ionosphere and the presence of significant vertical winds. The derived winds were compared with the meridional winds measured by the FPI. For each night, the value of the O⁺-O collision parameter which produced the best agreement between the two data sets was found. The precision of the collision frequency found in this way depends on the accuracy of the data. The statistical method was critically examined in an attempt to account for the variability in the data sets. This study revealed that systematic errors in the data, if unaccounted for by the analysis, have a tendency to increase the value of the derived collision frequency. Previous analyses did not weight each data set in order to account for the quality of the data; an improved method of analysis is suggested.  相似文献   

Association announcements     

John C. Davis 《Mathematical Geosciences》1982,14(6):679-681

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Reviews in mineralogy,volume 10, characterization of metamorphism through mineral equilibria: edited by John M. Ferry,Mineralogical Society of America, 1982, 397 pp. $8.00     

Raymond Joesten 《Geochimica et cosmochimica acta》1983,47(7):1335-1336

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Impacts of Present and Future Climate Change and Climate Variability on Agriculture in the Temperate Regions: North America   总被引：2，自引：0，他引：2  

Raymond P. Motha  Wolfgang Baier 《Climatic change》2005,70(1-2):137-164

The potential impact of climate variability and climate change on agricultural production in the United States and Canada varies generally by latitude. Largest reductions are projected in southern crop areas due to increased temperatures and reduced water availability. A longer growing season and projected increases in CO₂ may enhance crop yields in northern growing areas. Major factors in these scenarios analyzes are increased drought tendencies and more extreme weather events, both of which are detrimental to agriculture. Increasing competition for water between agriculture and non-agricultural users also focuses attention on water management issues. Agriculture also has impact on the greenhouse gas balance. Forests and soils are natural sinks for CO₂. Removal of forests and changes in land use, associated with the conversion from rural to urban domains, alters these natural sinks. Agricultural livestock and rice cultivation are leading contributors to methane emission into the atmosphere. The application of fertilizers is also a significant contributor to nitrous oxide emission into the atmosphere. Thus, efficient management strategies in agriculture can play an important role in managing the sources and sinks of greenhouse gases. Forest and land management can be effective tools in mitigating the greenhouse effect.  相似文献   

Glacial isostatic adjustment on a rotating earth     

Jerry X. Mitrovica  Glenn A. Milne  James L. Davis 《Geophysical Journal International》2001,147(3):562-578

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