摘要:

We determined lunar semidiurnal (M2) and diurnal luni‐solar (O1) tides of the meridional winds observed for two years between 1979 and 1980 by the Kyoto meteor radar. At 95 km altitude, the M2and O1tidal wind of 2.2 m/sec and 1.2 m/sec were observed. From the downward phase progression with altitude, the vertical wavelength was estimated as 60 and 25 km for the M2and O1component, respectively. Seasonal variation of the M2tidal wind was detected. Lunar variation has also been detected in the mean height of meteor echoes. The amplitude for the M2and O1component was 0.22 and 0.18 km, with the maximum height occurring at 9.4 and 14.1 hrs lunar time, respectivel

ISSN:0094-8276    

DOI:10.1029/GL008i003p00191

年代:1981

数据来源: WILEY

摘要:

Subsidence over an underground cavity is modeled by assuming the subsiding region to be an infinitely long elastic layer that rests on a rigid base and deforms under its own weight into an opening under its lower surface. An approximate analytic solution based on Fourier transform methods is found for vertical displacements of the ground surface and the roof of the opening when the layer thickness is much greater than the width of the opening. This model differs from previous analytic models in allowing both the ground surface and cavity roof to be traction‐free. The shape of the surface subsidence trough is found to be controlled by the ratio of the layer thickness to the width of the opening; as the value of this ratio decreases the subsidence trough narrows and a peripheral ridge form

ISSN:0094-8276    

DOI:10.1029/GL008i003p00195

年代:1981

数据来源: WILEY

摘要:

The theory of membrane tectonics proposed by Turcotte and Oxburgh [1973] to explain intraplate tensional features and earthquakes, and developed by Turcotte [1974]for an elastic lithospheric membrane, is extended to the case of a viscoelastic lithosphere. Such an extension may be expected to seriously modify the theory since, for all lithospheric viscosities except the very highest, the time scale for viscous relaxation is comparable to the time scale for changes in plate curvature. It is found that for most viscosities considered, the membrane stresses generated by changes in plate curvature do not exceed ∼10² bars. We conclude that either the effective viscosity of the lithosphere is much higher than indicated by most studies, or membrane tectonic stresses play a secondary role in the generation of intraplate features and earthquak

ISSN:0094-8276    

DOI:10.1029/GL008i003p00199

年代:1981

数据来源: WILEY

摘要:

Geophysical experiments on Iceland and adjacent areas suggest that crustal thickening due to underplating provides a significant contribution to mechanisms of crustal genesis in this region. According to this model, mantle derived melt accumulates in a thin layer (T<4km) at the base of the crust beneath the neovolcanic zone. With time, this melt cools, solidifies, and accretes to the base of the crust leading to crustal thickening. The crust increases in thickness from 8‐10 km directly beneath the neovolcanic zone to an average value of 20 km for the generally older (∼10 my) Iceland plateau. The much older Iceland‐Faeroe Ridge has a crustal thickness of 30 km. Therefore, segregation of material from a significant volume of the mantle and continued crustal underplating may persist well beyond the boundaries of surface manifestations of volcanic activity. Hence, crustal genesis may continue beneath regions as old as 10 my at the su

ISSN:0094-8276    

DOI:10.1029/GL008i003p00203

年代:1981

数据来源: WILEY

摘要:

High‐frequency Pn,Sn velocities for earthquakes originating in the subduction zones of the Western Pacific suggest that the travel paths of these phases, recorded in the range of 12° to 30°, may be significantly different from those of Pn,Sn phases recorded at distances less than 12° or greater than 30°. This suggestion is supported by high‐frequency Pn,Sn velocities for intra‐plate earthquakes in the Central and Sout

ISSN:0094-8276    

DOI:10.1029/GL008i003p00207

年代:1981

数据来源: WILEY

摘要:

A thermal penetrator that was air dropped into a freshly emplaced pumice flow at Mt. St. Helens yielded information on the in‐situ thermal properties of the pumice. The in‐situ conductivity‐density‐specific heat product at a depth of 60 cm was found to be 7.24 × 10−5cal²/cm4s−°C² at an average pumice temperature of 200°C. Using this data, values for the average in‐situ thermal conductivity (2.9 × 10−4cal/cm−s−°C) and thermal diffusivity (1.2 × 10−3cm²/s) were estimated. These thermal properties are of use in studies of pumice cooling and in the interpretation o

ISSN:0094-8276    

DOI:10.1029/GL008i003p00210

年代:1981

数据来源: WILEY

摘要:

Ash from the 18 May 1980 eruption of Mount St. Helens deposited from air faithfully records the direction of the local geomagnetic field in eastern Washington, whereas ash settled from suspension in water in fluvial environments exhibits significant inclination and current‐rotation errors in magnetic direction similar to those reported in other subaqueously deposited sediments. The current‐rotation errors are associated with partial alignment of the major axes of magnetic susceptibility in the direction of water currents. Subaerial deposition produces strong stable remanent magnetization in ash with or without postdepositional wetting by r

ISSN:0094-8276    

DOI:10.1029/GL008i003p00213

年代:1981

数据来源: WILEY

摘要:

Viscous remanent magnetization acquisition and decay coefficients are shown to be strongly affected by the previous magnetic history of the samples. Demagnetization of coarse grain, multi‐domain, magnetite samples using alternating magnetic fields causes a sharp reduction in the ability to acquire viscous magnetization. VRM acquisition in single‐domain particles is not affected by AF demagnetization but is sensitive to the amount of time the sample is kept in zero magnetic field storage prior to applying the VRM field. VRM acquisition coefficients are strongly dependent on magnetic grain size with high values at both very small and very large grain diamet

ISSN:0094-8276    

DOI:10.1029/GL008i003p00217

年代:1981

数据来源: WILEY

摘要:

Pollutants from coal‐fired power plants increase the drop modal radii and broaden the drop spectra of stratocumulus clouds. Additional water from the coal combustion leads to a measurable increase of the liquid water content of polluted clouds. Implied consequences are an increase of the coalescence efficiency, and an increase in acidity, of affected cloud

ISSN:0094-8276    

DOI:10.1029/GL008i003p00221

年代:1981

数据来源: WILEY

摘要:

Water levels in the Los Angeles Aqueduct in southern California fluctuate in a manner that are not easily attributable to normal aqueduct operations. Simple hydraulics suggests that large scale earth tilt can register as water level anomalies with a sensitivity of about .01 ft/microradian. Two aqueduct anomalies which coincide spatially and temporally with independently observed deformational phenomena are used to explore this suggestion.

ISSN:0094-8276    

DOI:10.1029/GL008i003p00225

年代:1981

数据来源: WILEY