bluuebunny/crossref_metadata_2025_split huggingface dataset:
10th of April 1987 seismic swarm: Correlation with geochemical parameters in Campi Flegrei Caldera (southern Italy)
Authors: Tedesco Dario , Bottiglieri Luisa , Pece Raimondo 
Published: February 2008

A close relationship between geophysical activity (seismicity and ground deformation) and chemical changes in volcanic reservoirs has been proposed several times in active volcanic areas. In Campi Flegrei caldera, especially during the bradyseismic crisis which occurred between 1982‐1984, this correlation was never clearly demonstrated because of the high rate of occurrence of earthquakes and the small number of gas samples.After at least two years of both geochemically and geophysically quiescent period, a swarm of 50 earthquakes, felt in the area of the Solfatara crater with 2.0 maximum magnitude, occurred on the 10th of April 1987. At about the same time (before and after), several geochemical parameters showed important changes in concentration. These include water vapour, nitrogen, hydrogen, methane and to a lesser extent hydrogen sulfide in fumarolic gases from Bocca Grande fumarole in the Solfatara crater and the radon content in water wells situated far from the swarm epicentral area. In our opinion, the processes causing the geochemical changes are linked to aseismic creeping mechanisms, which leads to an easier rising of fluids in fumaroles (H2O, N2, H2 and CH4) and in the superficial water table (Rn).The subsequent seismicity could be related to consequent local stress accumulation on gas reservoir rocks induced by creeping.
Lateral variations in upper mantle thermal structure inferred from three‐dimensional seismic inversion models
Authors: Yan Ben , Graham E. K. , Furlong K. P. 
Published: February 2008

Global shear wave velocity variations in the upper mantle (Woodhouse and Dziewonski, 1984) are employed as a basis for inferring lateral heterogeneities in temperature or composition at a depth of 150 km. Using experimentally determined elastic moduli for the olivine solid solution and Hashin‐Shtrikman bound theory, Vs and its partial derivatives with respect to temperature or composition (iron content) are calculated for the depth of interest. Based on these results, the observed seismic Vs variations are interpreted as temperature and compositional deviations relative to a spherically symmetric reference model.If it is assumed that the Vs variations primarily represent lateral temperature changes, then the present results can be used to construct a global surface heat flow map from the geotherm families of Pollack and Chapman (1977). Our inferred heat flow patterns, calculated independently of actual heat flow data, show clear agreement with the surface heat flow maps proposed by Chapman and Pollack (1975) and Chapman (1985). This result is consistent with and supports thermal structure as the primary governing factor in the generation of upper mantle lateral velocity variations. Compositional changes appear to correlate with temperature, but affect velocity structure to a lesser extent.
Aspera/Phobos measurements of the ion outflow from the MARTIAN ionosphere
Authors: Lundin R. , Zakharov A. , Pellinen R. , Barabasj S. W. , Borg H. , Dubinin E. M. , Hultqvist B. , Koskinen H. , Liede I. , Pissarenko N. 
Published: February 2008

This report reviews the first results on the ionospheric ion outflow in the Martian magnetosphere by the ion composition experiment ASPERA on Phobos‐2. The measurements show that Mars is characterized by a strong loss of plasma from its topside ionosphere. This loss results from both ion pick‐up due to mass‐loading of the solar wind in the Martian boundary layer and an acceleration mechanism, quite similar to that observed above the Earth's auroral oval, providing intense ionospheric O+ beams of energies up to several keV.A preliminary estimate of the ionospheric outflow from Mars indicates that the planet at present is losing oxygen at a rate of ≈3·1025 ions/s. This corresponds to an evacuation of its present total atmospheric oxygen content (contained in CO2 and O2) in less than 100 million years.
Downward propagation of upper stratospheric mean zonal wind perturbation to the troposphere
Authors: Kodera Kunihiko , Yamazaki Koji , Chiba Masaru , Shibata Kiyotaka 
Published: February 2008

An investigation is conducted to determine the influence of changes in the upper stratospheric mean zonal wind on the circulation of the lower atmosphere. In addition to observed data, results of numerical experiments with a general circulation model are used, in which the solar ultraviolet heating rate is varied to force changes in the mean zonal wind in the upper stratosphere.It is found that when the upper stratospheric mid‐latitude westerlies are strong during December, lower stratospheric polar night jet is persistent and the westerlies in the polar region of the troposphere become stronger in the following February. These results are common to both the observations and the numerical experiments.
Formation of nitric acid hydrates ‐ A chemical equilibrium approach
Authors: Smith Roland H. 
Published: February 2008

Published data are used to calculate equilibrium constants for the reactions over the temperature range 190 to 205 K. Standard enthalpies of formation and standard entropies are calculated for the tri‐ and mono‐hydrates. These are shown to be in reasonable agreement with earlier calorimetric measurements. The formation of nitric acid trihydrate in the polar stratosphere is discussed in terms of these equilibrium constants.
Fast dual tomography
Authors: Carrion Philip M. 
Published: February 2008

This paper can be considered as a continuation of the work by Carrion and Carneiro (1989), where a generalized approach to linearized inversion of geophysical data was developed. Their method allows one to incorporate virtually any constraints in the inversion and reformulate the problem in the dual space of Langrangian multipliers (see also Carrion, 1989a). The constrained tomography makes traveltime inversion robust: it automatically rejects “bad data” which correspond to solutions beyond the chosen constraints and allows one to start inversion with an arbitrary chosen initial model.In this paper, I will derive basic formulas for constrained tomographic imaging that can be used in such areas of geophysics as global mapping of the earth interior, exploration geophysics, etc. The method is fast: an example that will be shown in the paper took only 6 min. of VAX CPU time. Had the conventional least‐squares matrix inversion been used it would have taken more than 10 hours of the CPU time to solve the same problem.
The magnetosphere of Neptune: Its response to daily rotation
Authors: Voigt Gerd‐Hannes , Ness Norman F. 
Published: February 2008

The Neptunian magnetosphere periodically changes every eight hours between a “pole‐on” magnetosphere with only one polar cusp and an “Earth‐type” magnetosphere with two polar cusps. In the “pole‐on” configuration, the tail current sheet has an almost circular shape with plasma currents closing entirely within the magnetosphere. Eight hours later the tail current sheet assumes an atmost flat shape with plasma currents touching the magnetotail boundary and closing over the tail magnetopause.We have calculated magnetic field and tail current sheet configurations in a three‐dimensional model, but have investigated the plasma‐ and thermodynamic conditions in a simplified two‐dimensional MHD equilibrium magnetosphere. By matching the asymptotic plasma sheet β = 2μ0P/B2 values in the two models, we found to our surprise that the free energy F in the tail region of the two‐dimensional model becomes independent of the dipole tilt angle. We conjecture that the Neptunian magnetotail might assume quasi‐static equilibrium states that make the free energy of the system independent of its daily rotation.
Cooling of slow solar wind protons from the Helios 1 Experiment
Authors: Eyni Menashe , Steinitz Raphael 
Published: February 2008

In a recent survey of initial results of the Helios experiment, Rosenbauer et al. [1977] suggested that there could be two types of solar wind, characterized by a ‘slow’ and a ‘fast’ component. This idea is based mostly on two distinct ranges of observed flow speed and on a preliminary analysis of data showing that the protons in the slow component expand nearly isothermally.Contrary to this result, we have found from the same data that the slow protons in the solar wind do clearly exhibit cooling, compatible with adiabatic expansion. For the analysis we used the data published by Rosenbauer et al. [1977] and treated them as we did in our previous analysis of the Mariner 2 data [Eyni and Steinitz, 1978]. The essence of our analysis is twofold: (1) the reduction of the strong dependence of temperature T on velocity u by the definition of a reduced temperature τ ≡ T/u2 and (2) the choice of samples which are as uniform as possible in velocity u and in (distance) normalized density n.
A case study of the aurora, high‐latitude ionosphere, and particle precipitation during near‐steady state conditions
Authors: Winningham J. D. , Anger C. D. , Shepherd G. G. , Weber E. J. , Wagner R. A. 
Published: February 2008

An Isis 2 pass is singled out for a detailed examination of the particle fluxes, optical emissions, and ionospheric parameters observed during a quiescent period (late recovery) between two substorms. This pass was chosen because it was part of a coordinated data acquisition period between the Air Force Geophysics Laboratory (AFGL) Airborne Ionospheric Observatory, Isis 2, and DMSP (Defense Meteorological Satellite Program). As a result, both long‐duration measurements (aircraft) and transient, snapshot (spacecraft) data are available. This allows, on a macroscopic level, the separation of space and time effects.On the basis of the joint data set it was established that the latitudinal morphology observed by the satellite is basically spatial in nature. It is concluded that the observed particle fluxes are most easily understood in terms of precipitation from the quiet time plasma sheet without intervening acceleration. The observed optical emissions and ionospheric parameters are found to be in good qualitative and quantitative agreement (within experimental error) with the electron fluxes, although establishment of this point has required careful determination of the viewing direction of the optical instruments, removal of scattered light (albedo) from underlying cloud and snow, and consideration of the effects of photon‐counting statistics on contour plots of the optical data.
Using dual‐well seismic measurements to infer the mechanical properties of a Hot Dry Rock Geothermal System
Authors: Fehler Michael 
Published: February 2008

High‐frequency (8–15 kHz) seismic waves that travel between two boreholes are used to probe the detailed structure of rock in the Los Alamos National Laboratory Fenton Hill hot dry rock geothermal energy reservoir. We study travel times of direct P waves and spectral characteristics of waveforms in an effort to determine whether or not large fluid‐filled fractures are present in the rock between the two boreholes. Data from two experiments, separated in time by 1 year, are studied. We find dramatic differences between the two experiments in P wave velocity and in spectral characteristics of waveforms that traversed the same region. We also find variations in P wave velocity and spectra as a function of location during one experiment.Loss of high‐frequency content of direct‐arriving P waves during the second dual‐well seismic experiment is compared with Q, found by using the coda wave technique (Aki and Chouet, 1975), and also with theoretical results on frequency dependence of transmission through a water‐filled fracture to determine the minimum number of large fractures in the system. Two to four fractures with thickness about 4 mm and vertical extent of as much as 200 m are required to explain observations during the second experiment. Efficient transmission of high frequencies observed during the first experiment is interpreted as meaning that fracture thickness was less than 1 mm at that time. Increased fracture thickness during the second experiment is probably due to a 75‐day period of heat extraction during which in situ temperature dropped by as much as 100° below the virgin temperature. Since the coefficient of linear thermal expansion of granite is approximately 10−5/°C, a decrease in temperature of 100°C in a region on the order of 1 m around the fracture is required to explain the increased fracture thickness.
Long‐term fault creep observations in central California
Authors: Schulz Sandra S. , Mavko Gerald M. , Burford Robert O. , Stuart William D. 
Published: February 2008

The U.S. Geological Survey (USGS) has been monitoring aseismic fault slip in central California for more than 10 years as part of an earthquake prediction experiment. Since 1968, the USGS creep network has grown from one creep meter at the Cienega Winery south of Hollister to a 44‐station network that stretches from Hayward, east of San Francisco Bay, to Palmdale in southern California. In general, the long‐term slip pattern is most variable on sections of the faults where several magnitude 4 and larger earthquakes occurred during the recording period (e.g., Calaveras fault near Hollister and San Andreas fault between San Juan Bautista and Bear Valley). These fault sections are the most difficult to characterize with a single long‐term slip rate. In contrast, sections of the faults that are seismically relatively quiet (e.g., San Andreas fault between Bear Valley and Parkfield) produce the steadiest creep records and are easiest to fit with a single long‐term slip rate.Appendix is available with entire article on microfiche. Order from the American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document J82‐004; $1.00. Payment must accompany order.
S‐P wave travel time residuals and lateral inhomogeneity in the mantle beneath Tibet and the Himalaya
Authors: Molnar Peter , Chen Wang‐Ping 
Published: February 2008

The average S wave travel time residuals from 11 earthquakes each in Tibet and the Himalaya imply that there are marked lateral variations in structure beneath Tibet and the Himalaya. Average S‐P wave residuals, measured with respect to the Jeffreys‐Bullen (J‐B) tables, for each of 11 earthquakes in the Himalaya are less than +1 s. Average J‐B S‐P residuals from 10 of 11 earthquakes in Tibet, however, are greater than +1 s, even when corrected for the large crustal thickness of Tibet. The largest values, 2.5, 3.2, 3.8, 4.5, and 4.9 s, are for five events in central and northern Tibet, and they imply that the average velocities in the crust and upper mantle of these portions of Tibet are 4–10% lower than those beneath the Himalaya. Therefore it is unlikely that a shield structure underlies these parts of Tibet, unless these S‐P residuals are due to variations in structure deeper than 250 km. S‐P residuals from two other events each in western and eastern Tibet are 1–2 s late and hence suggest that velocities beneath these areas are also somewhat lower than beneath shields. The mean S wave velocity seems not only to be different beneath Tibet and the Himalaya but also seems to increase from a minimum beneath northern Tibet to values close to those of the average earth toward the east, south, and west.Appendix A is available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009. Document B84‐010; $2.50. Payment must accompany order.
Introduction to Special Section on the Geological, Geophysical, and Tectonic Setting of the Cascade Range
Authors: Muffler L. J. Patrick 
Published: February 2008

The Cascade Range is an active volcanic arc that is formed by the subduction of the Juan de Fuca plate system beneath North America [Riddihough, 1978]. Knowledge of the Cascade Range, its volcanic rocks, and its tectonic setting is not only of broad scientific interest but also bears directly upon the estimation of geothermal resources and the evaluation of volcanic and seismic hazards.An understanding of the regional aspects of the Cascade Range is at the present time particularly important to the assessment of geothermal resources. Although identified geothermal resources in the Cascade Range are modest [Brook et al., 1979], substantial undiscovered geothermal resources have been inferred [e.g., Brook et al., 1979; Black et al., 1983; Bloomquist et al., 1985], primarily from the favorable volcanic and tectonic setting but also from high regional heat flow along the Cascade Range [Blackwell et al., 1982]. Consequently, a multiyear, multidisciplinary program of studies to refine the geothermal resource estimates of the Cascade Range is a major objective of the U.S. Geological Survey (USGS) Geothermal Research Program [Muffler, 1987]. The smallest and easiest part of this effort is an updated inventory of known hydrothermal convection systems. A much larger and far more difficult task is the estimation of the undiscovered geothermal resources. Existing drill hole information in the Cascade Range is sparse, and under the foreseeable economic climate, direct evaluation of the thermal regime by numerous deep holes is unlikely. However, the magnitude of the undiscovered geothermal resources can be addressed indirectly by an analysis of the tectonic, geophysical, volcanic, and hydrologie setting of the Cascade Range, thus allowing extrapolation of available drill hole data.
The Western Mediterranean Circulation Experiment (WMCE): Introduction
Authors: La Violette Paul E. 
Published: February 2008

The purpose of the Western Mediterranean Circulation Experiment was to study the circulation of the western Mediterranean Sea from the Strait of Sicily to the Strait of Gibraltar using scales ranging from basin‐size to 1 km and depths from the surface to the deepest layers. An international consortium of multidisciplined marine investigators formed its study group; each had programs adapted to achieve the common goal: to derive the spatial and temporal variability of the western Mediterranean Sea circulation.WMCE was a logical outgrowth of a number of field campaigns and data analyses (see, for example, Donde Va? Group [1984]) that raised as many questions as answers. The WMCE Consortium was formed during a 1983 NATO (North Atlantic Treaty Organization) study meeting in La Spezia, Italy, when the time and resources were judged appropriate for a study of the western Mediterranean as a single entity. Such a study would answer the following questions:1. What are the major features of the western Mediterranean circulation, and how do they vary in space and time?2. What are the physical forcing mechanisms?3. How can this knowledge be implemented into numerical models?4. How does the circulation affect the chemical, biological, and optical properties of the western Mediterranean Sea?
Charged particles in the magnetosphere
Authors: Van Allen James A. 
Published: February 2008

The object of this paper is to review observational work by the University of Iowa having to do with the dynamics of the population of charged particles in the outer radiation zone of the earth's magnetosphere.Specific topics are as follows:a. Intensity fluctuations and apparent lifetimes of outer zone electrons having kinetic energies E6 ranging from 40 kev to several Mev.b. Ring current particles, protons and electrons EPJ E6 ^> 200 ev.c. Geomagnetically trapped a particles, 2.09 < Ea < 15 Mev.d. The electric field in the magnetospheric tail.The spirit of the discussion is to invite attention to a number of phenomena that appear sufficiently well established and significant to merit substantial interpretative effort.
Structure and secular change of the geomagnetic field
Authors: Cain Joseph C. 
Published: February 2008

This report is a review of some of the recent developments in the knowledge of the structure and secular variation of the main geomagnetic field. It is hoped that this discussion will help to complement and update the excellent summary given by Zmuda [1973].Many past papers have imbedded in them such phrases as ‘lack of adequate data, ‘uncertainty of high‐order coefficients’ and other qualifiers that lead the reader to infer that the numerical models (and maps) have large errors or that the conclusions of the studies must be considered tentative. The recent comprehensive global mapping of the field by near‐earth satellites, in scalar magnitude only, has partially quelled such statements and shown that many of the prior results were approximately correct. Confusion has often arisen since attention was focused on the fact that many of the individual higher‐order coefficients of the spherical harmonic expansions did not agree when computed by different analyses [see, e.g., Zmuda, 1971, p. 148]. It has now become evident that it is more meaningful to compare the spatial structure represented by the sum of the functions than to place undue emphasis on the correspondence of each individual term. This is true because aliasing is dependent on the degree of expansion and data distribution, so that two sets of coefficients can differ slightly in phase and amplitude and yet be fairly consistent with the data in most areas.
Progress in seismological instrumentation
Authors: Smith Stewart W. 
Published: February 2008

The period since 1970 has been marked by significant engineering advances in conventional seismic instrumentation as well as some fundamental developments in laser technology with direct application in earth strain measurement and geodesy.In the area of conventional seismic instrumentation the engineering development of borehole long‐period seismographs has made possible the siting of this type of instrumentation independent of the usual requirements for underground vaults. This field has been extensively reviewed by Melton [1975]. The work in long‐period instrument development has led to a better understanding of the fundamental limitations of ground noise at long period [Fix, 1972]. At very long period the development of a superconducting gravimeter by Prothero and Goodkind [1972] has demonstrated stability over periods of time unattainable with systems utilizing conventional mechanical suspensions.
Cosmogony of the solar system
Authors: Ward William R. 
Published: February 2008

This report is intended to cover research on solar system origin over the last 4 years. Emphasis has been placed on the physics of planetary accumulation mechanisms, although pertinent references on the chemistry of mineral condensation and cometary research are included.The most ambitious attempt to model the solar nebula to date is the 1973 paper of Cameron and Pine [1973]. This model is characterized by a large mass (∼2MS) and is modeled as a collapse of spherical distribution of gas with an angular momentum per unit mass estimated from the assumption of fully developed turbulent motion. A disk structure is determined by requiring a radial and vertical balance of forces, i.e., gravitational, centrifugal, and pressure gradient forces. The most striking and controversial feature of the model is the absence of a central concentration of material representing the protosun. Rather, the sun forms as a secondary process of angular momentum redistribution via Eddington‐Sweet type circulation currents during which the inner portion of the nebula contracts and the outer portion expands radially. The large mass of the system is justified on two counts: there must be sufficient material to allow angular momentum redistribution, and a T‐tauri phase has presumably ejected a few tenths of a solar mass from the system. Another noteworthy attribute of the model is the presence of a vertical convection zone between ∼1 and ∼10 AU due to the opacity of condensed iron grains.