摘要:

An inverse relationship exists between the summit deflation of Kilauea, as recorded by summit tilt, and the elevation of associated eruptive vents on the East Rift Zone. This relationship implies that East Rift eruptions drain the summit magma reservoir to pressure levels that are dependent on the elevation of the eruptive vents.

ISSN:0094-8276    

DOI:10.1029/GL010i007p00493

年代:1983

数据来源: WILEY

摘要:

An alternative to the method of Langston (1982) for determining fault‐plane solutions from a single 3‐component seismic station is proposed. The method calculates synthetic P and SH seismograms for three basic orientations of a shear dislocation embedded in a plane layered Earth model, and uses least‐squares to minimise the error between the observed data and a linear sum of the synthetic seismograms. The result is five trigonometric functions of fault strike θ, fault dip δ, and rake of the slip vector λ. When applied to the Borrego Mountain event of 9 April 1968, the method provides a solution which is in close agreement with well‐constrained studies of the

ISSN:0094-8276    

DOI:10.1029/GL010i007p00497

年代:1983

数据来源: WILEY

摘要:

New Hugoniot data on single crystal diopside, CaMgSi2O6(Di), suggest that transformation to a high‐pressure thermomechanical state begins at ∼50 GPa and is complete above 100 GPa, in agreement with other pyroxenes and silicates of geophysical interest. Comparison of the new high pressure phase (HPP) data for Di and salite, CaMg0.82Fe0.18Si2O6(Sa) with appropriate mixed oxide and perovskite models implies compatibility between either model and the data. Conversely, least‐squares fits to the HPP Di data favor lower (3.6 ‐ 3.9 Mg/m³) values of zero‐pressure, room‐temperature density than the models (4.0 ‐ 4.1 Mg/m³). Similar comments apply to porosity‐corrected HPP hedenbergite (Hd) data. The HPP Di, Sa, and Hd data also imply much larger density differences between these compositions in the HPP regime (e.g., ≈0.8 Mg/m³ between Di and Hd) than at STP (0.38 Mg/m³). This may represent the influence of multiple transition processes (e.g., polymorphism and Fe2+high‐low spin) as a function of Fe content across the Di‐Hd series. The new HPP Sa data closely parallel (≈0.1 Mg/m³ less dense) the lower mantle density profile from ∼90 GPa to 136 GPa. Our results are consistent with the speculations of Jeanloz and Ahrens on the possibility of sign

ISSN:0094-8276    

DOI:10.1029/GL010i007p00501

年代:1983

数据来源: WILEY

摘要:

The axial traces of the major Appalachian folds change azimuthal direction from a NE‐SW orientation to a N‐S orientation in the area of the Pennsylvania Salient and swing back to a NE‐SW orientation in the vicinity of the Virginia Reentrant. All available paleomagnetic data from the folded Appalachians have been examined to test the Appalachian orocline hypothesis. Pre‐deformational site‐mean directions from suitable studies were rotated by the amount required to bring the strike of the sampled beds into coincidence with an average trend of the Central and Southern Appalachians (N35E). A comparison of clustering of site‐means before and after this correction, reveals that in all cases unbending of the arc causes site‐mean directions to disperse. This dispersal demonstrates that the curvature of the Appalachian orogen is to a very large degree a primary feature rather than a feature which resulted from the bending of initially strai

ISSN:0094-8276    

DOI:10.1029/GL010i007p00505

年代:1983

数据来源: WILEY

摘要:

Recent satellite measurements of the solar total irradiance (S) indicate that on time scales of days to months the solar constant varies by a few tenths of a percent. The predominant part of these variations can be explained by blocking of the upward solar flux by sunspots. The observations are consistent with current theoretical models of energy storage in which the energy blocked by the sunspots is temporarily stored in the convective zone. We present modelled solar constant variations on a day by day basis selected from model calculations for the period 1874 through 1981 (Hoyt and Eddy, 1982). Because neither faculae nor bright rings about sunspots balance the net blocking by sunspots, there is a net eleven year modulation in irradiance with a relative depression of as much as 0.07% for the period 1969‐1981. The model is compared with satellite observations and to other recently published models that impose immediate reradiation of blocked flux and therefore fail to predict an eleven year modulation of

ISSN:0094-8276    

DOI:10.1029/GL010i007p00509

年代:1983

数据来源: WILEY

摘要:

In order to study the mechanism of aerosol sulfate formation, weekly samples of SO2and aerosol SO4=were collected at Hubbard Brook Experimental Forest, West Thornton, New Hampshire from July to December, 1980. Samples were analyzed for concentration and sulfur isotopes (δ34S). Late summer‐early fall samples are characterized by high, variable SO4=levels and low SO2levels, while late fall ‐ early winter samples exhibit low SO4=and high SO2levels. These trends suggest that the oxidation rate varies seasonally, with faster oxidation during warmer months. The sulfur isotopic fractionation between aerosol SO4=and SO2is intermediate between that expected from homogeneous and heterogeneous reactions, indicating that both processes can be important. The isotopic data suggest that homogeneous oxidation reactions are more important than solution reactions, particularly during warm mo

ISSN:0094-8276    

DOI:10.1029/GL010i007p00513

年代:1983

数据来源: WILEY

摘要:

The existence of oxalate (COO)2=in tropospheric aerosols and in precipitation has been demonstrated using ion chromatography. Mixing ratios have been observed up to 50 pptv in air samples and 0.3 ppm in precipitation. Correlation of airborne oxalate with airborne nitrate suggests a pollution source.

ISSN:0094-8276    

DOI:10.1029/GL010i007p00517

年代:1983

数据来源: WILEY

摘要:

High‐resolution solar observations covering the 8 to 13 µm atmospheric window are now being carried out routinely at the Kitt Peak National Observatory (KPNO), Tucson, Arizona, using a 1 meter‐path difference Fourier transform spectrometer. Such observations allow the simultaneous measurement of a large number of trace gases. Preliminary results for the three most important fluorocarbons, FC‐11, FC‐12 and FC‐22 are reported here. These results, in the form of average mixing ratios, show the potential and illustrate the performance of the Kitt Peak interferometer for this a

ISSN:0094-8276    

DOI:10.1029/GL010i007p00521

年代:1983

数据来源: WILEY

摘要:

A numerical simulation is used to predict the interaction between the earth’s bow shock and lithium to be released in the solar wind during the Active Magnetospheric Particle Tracer Explorers program in 1984. Based on the simulation results for a release near the subsolar point, it is recommended that a favorable release condition is when the garden‐hose angle of the interplanetary magnetic field exceeds about 60 to 70° so that the transmission of Li+ions through the bow shock is optimized. The model also predicts that the Li+is “shock‐drift” accelerated at the bow shock. The energy gain of Li+ions is on the average less for the transmitted particles (below a factor of about 4) than for the reflected particles (below a factor of

ISSN:0094-8276    

DOI:10.1029/GL010i007p00525

年代:1983

数据来源: WILEY

摘要:

During the passage of a large interplanetary shock on 13 October 1981, the ISEE‐1 and ‐2 spacecraft were in the solar wind outside of the upstream region of the bow shock. The high time resolution data of the University of California particle instruments enable us to pinpoint the expected electron spike as occurring just before the magnetic ramp. In addition, two features that occur at this shock have not been observed before: 1) electron oscillations associated with low frequency waves upstream of the shock and 2) sharp ‘overshoot’ (∼1 sec) in the ion fluxes that occur right after the magnetic ramp. This interplanetary shock exhibits many of the same characteristics that are observed at the Earth’

ISSN:0094-8276    

DOI:10.1029/GL010i007p00529

年代:1983

数据来源: WILEY