bluuebunny/crossref_metadata_2025 huggingface dataset:
Isotopically anomalous 196Hg and 202Hg in Antarctic achondrites
Authors: Jovanovic S. , Reed G. W.
Published: February 2008

Antarctic shergottite EETA 79001 and polymict eucrite ALHA 78132 contain Hg which is anomalous in the 196Hg or 202Hg isotope. The anomalous fractions were extracted at 130°C during stepwise heating of neutron irradiated samples. The 196/202Hg ratios differ by factors of 2‐4 from the normal Hg ratio. This is an enormous effect. Approximately fifty other Hg fractions extracted at temperatures up to 1200°C from these and several other Antarctic basaltic achondrites and from the non‐Antarctic fall, Shergotty, gave 196/202Hg ratios within 20% of normal.
The propagation speed of a positive lightning return stroke
Authors: Idone Vincent P. , Orville Richard E. , Mach Douglas M. , Rust W. David
Published: February 2008

The first direct determination of the propagation speed of a lightning return stroke lowering positive charge to ground has been made. This stroke was the third of eight otherwise negative strokes in a triggered lightning flash initiated at the Kennedy Space Center, Florida. Two independent optical systems, one photographic and the other photoelectric, yielded common recordings for the third and fourth strokes; the respective two‐dimensional return stroke propagation speeds were 1.0 vs. 0.93 ×108 m/s for the positive (third) stroke and 1.0 vs. 1.0 ×108 m/s for the fourth stroke. Using fast electric‐field data, we estimated the positive stroke peak current to be 21 kA. Photoelectric data only yielded propagation speeds of 1.4, 1.6, 1.2, 1.3, 1.0 and 0.90 × 108 m/s for the first, second and fifth through eighth return strokes, respectively. All propagation speeds were evaluated over 850 m of channel near ground and have an error estimate of 10‐15%. For this positive stroke, we found a return stroke propagation speed typical of negative strokes. Whether positive return strokes, in general, travel at typical negative return stroke speeds must await future measurements.
A method for evaluating the total magnetospheric energy output independently of the ε parameter
Authors: Vasyliūnas Vytenis M.
Published: February 2008

The calculated value of the energy consumption rate UT within the near‐Earth and middle magnetosphere depends significantly on the assumed loss time τ of the ring current, which is known not to be a constant. In much previous work, τ was taken to be a function of a combination of solar wind quantities (the ε parameter) assumed to represent the solar wind energy input into the magnetosphere. This may lead to problems of circular reasoning and artificial interdependence of quantities when the statistical relation between UT and ε is investigated. To avoid these problems, I propose that τ be taken as a function not of ε but of UT itself. Values of UT independent of ε or any other similar solar wind quantity can then be obtained at a cost of only a modest increase of computational effort.
Shallow paleomagnetic directions from historic lava flows, Hawaii
Authors: Castro Joyce , Brown Laurie
Published: February 2008

A study designed to examine the basic theory of thermoremanent magnetization acquisition parallel to the earth's ambient magnetic field upon cooling and to evaluate intra‐flow variations of very young basalt flows has yielded some startling initial results. Two extensively sampled flows, the 1950 flow of Mauna Loa and the 1972 flow from Mauna Ulu, Kilauea, have been found to have paleomagnetic directions statistically different from the present geomagnetic field direction (PFD) in Hawaii. The 1950 flow shows very consistent, but shallow directions throughout the flow, with a mean inclination 6° shallower than the PFD. Directions from the 1972 flow vary from site to site both along the length of the unit and within vertical sections. Relative between site consistency is low, with all sites but one having paleomagnetic directions distinct from the PFD, however, the mean inclination for this flow, 33.4°, is only about 3° shallower than expected. The source of such anomalous behavior in the recording of ambient field directions is yet unknown, although several possible causes are examined.
Helium isotopic evidence for recent subcrustal volcanism in eastern Australia
Authors: Torgersen T. , Clarke W. B. , Habermehl M. A.
Published: February 2008

A component with ∼6% mantle helium (³He/4He=5‐9×10−7) has been identified in borewaters from the Great Artesian Basin, Australia that is isotopically distinct from previously identified in situ production (³He/4He = 1.6×10−8) and a crustal degassing flux (³He/4He = 6.75×10−8). The occurrence of this component is limited to three identified localities (∼20.5°S 144°E; ∼25.5°S 146°E; ∼27°S 144.5°E) all within the region of high reduced heat flow in eastern Australia. No evidence for a mantle component was apparent in central Australia. This component is most probably the result of continued intrusive volcanism (<1 m.y.) associated with the Cainozoic lava flow fields in the region. Although the volcanic activity has no present‐day surface manifestation, its mantle helium was probably carried to the near‐surface by large‐scale fluid transport processes in the crust.
Magnetic anomalies around the North Anatolian Fault
Authors: Charrette E. E. , Toksöz M. Nafi
Published: February 2008

The nature of the observed magnetic anomalies surrounding the San Andreas fault (SAF) is of interest to researchers studying fault kinematics and earthquake dynamics. In this work we will present and interpret data collected around the North Anatolian fault (NAF) by Honkura et al. (1985) which exhibit anomalies similar to those observed along the SAF. Magnetic and surface geologic data from five profiles straddling the North Anatolian Fault were used in conjunction with a two dimensional magnetic inversion in an attempt to identify the source of the magnetic anomalies. As a result of this study, we conclude that all long wavelength anomalies (λ ≥ 500m) could be attributed to the changes in the relative magnetic susceptibility across geologic units. Thus, they are due to lateral variations in the near surface geology and are not due to the concentration of a particular material in the fault zone. However, there was one exception, a short wavelength anomaly (λ ≃ 150m) was observed on profile IJ. Based on the results of the inversion, it appears that the anomaly may be due to a small sliver of material located in the upper part of the fault zone. If that interpretation is correct, the short wavelength anomaly is clearly of different nature than the other anomalies.
Comparison of total ozone amounts derived from satellite and ground‐based measurements
Authors: Planet Walter G. , Miller Alvin J. , Angell James K.
Published: February 2008

Total ozone amounts derived from the NOAA operational sounder (TOVS) are compared to measurements from Nimbus‐7 SBUV and ground‐based Dobson spectrophotometer observations over a seven‐year period. The global trends of the data, in terms of deviations from long‐term averages, derived from measurements by each satellite instrument show qualitative agreement until mid‐1984 when the data diverge with the TOVS‐derived data showing higher values. Additionally, more significant differences appear in both the north and south temperate zones' records. The trends derived from the satellite systems' measurements also show differences from that of the Dobson instrument measurements with the trend of the TOVS measurements showing generally better overall agreement with the Dobson data record.
For a lead‐temperature feedback in climatic variation
Authors: Ledley Tamara Shapiro
Published: February 2008

Sea ice is an important factor in controlling the exchange of energy between the ocean and atmosphere in the polar regions and has an important impact on climate. A climate model has been developed which enables analysis of the effect of changes in sea ice on the ocean‐atmosphere energy exchange and atmospheric temperature. The model results described here show that opening small areas of open ocean (leads) within the winter ice pack has a large impact on the atmospheric temperature of the polar regions. This effect is due to changes in the sensible heat flux between the surface and atmosphere resulting from leads. Thus leads within the ice pack may have significant impact on short and long term climatic variations.
Chernobyl radioactivity found in mid‐water sediment interceptors in the N. Pacific and Bering Sea
Authors: Kusakabe M. , Ku T.‐L. , Harada K. , Taguchi K. , Tsunogai S.
Published: February 2008

Fission‐product nuclides 134Cs, 137Cs and 103Ru originated from the Chernobyl accident have been detected in sediment traps deployed at mid‐water depths ranging from 110 to 780 m in the N. Pacific and the Bering Sea. The detected radioactivities, originally associated with fine airborne particles, have apparently been incorporated into much larger aggregates of predominantly biogenic material formed in the surface ocean, and transferred downward through the water column with velocities of the order of 100 m/day.
The old continental shields stability related to mantle convection
Authors: Mimouni Ali , Rabinowicz Michel
Published: February 2008

Two dimensional thermal convection of a fluid layer overlayed by a conductive lid is studied. Lateral thermal conductivity variation is assumed within the rigid lid, in order to see how an increase of the thermal conductivity within the lithosphere can stabilize a downwelling plume beneath it. Calculations are performed for a constant viscosity fluid with Rayleigh numbers (Ra) up to 4 × 105. Different lid thicknesses (δ) and thermal conductivity (k) values are considered. The numerical results reveal a coupling between the zone of high thermal conductivity and the downwelling plumes. The adjustment time of the convective circulation decreases when the values of parameters (Ra, δ, k) increase. The lowest value for the adjustment time (500 My), is obtained for Ra = 4 × 105. The calculations suggest that an increase of the effective thermal conductivity causes the anchoring of downwelling mantle jets below primitive continental nuclei. The presence of such sinking plumes attached to the cratonic lithosphere may protect them against disruption by mantle flow. The increase in the effective thermal conductivity of the cratonic lithosphere is attribued to thermal conductivity anisotropy of olivine crystal. Such a mechanism can explain the stability of old continental shields.
Solar‐terrestrial coupling: Low‐latitude thermospheric nitric oxide
Authors: Barth Charles A. , Tobiska W. Kent , Siskind David E. , Cleary David D.
Published: February 2008

As measured by the Solar Mesosphere Explorer satellite, the density of nitric oxide at low latitudes (30°S to 30°N) and at 110 km (E‐region) decreased from a mean value of 3 × 107 molecules/cm³ in January 1982 to a mean value of 4 × 106 molecules/cm³ in April 1985. In addition, the nitric oxide density varied ±50% with a 27‐day period during times of high solar activity. The variation of nitric oxide correlates with variations in the solar Lyman‐alpha irradiance which is also measured by the Solar Mesosphere Explorer satellite. The Lyman alpha irradiance is interpreted as an index of the variations in the solar EUV and soft X‐ray flux. The hypothesis is proposed that the solar X‐ray flux between 20 and 100 Å has a larger variation than the solar EUV flux between 100 and 1050 Å and that the solar X‐rays produce photoelectrons which are the source of the nitric oxide.
Far‐infrared measurement of stratospheric carbon monoxide
Authors: Abbas M. M. , Glenn M. J. , Nolt I. G. , Carli B. , Mencaraglia F. , Carlotti M.
Published: February 2008

The stratospheric vertical distribution of CO is obtained from balloon based far infrared limb thermal emission spectra by analyzing several limb sequences of the R8 and R1 spectral lines at 34.588 cm−1 and 49.932 cm−1 respectively. This constitutes the first determination of the stratospheric CO profile from infrared thermal emission spectra. The results indicating 24.6±7.6 ppbv at 21 km and 34.4±10.1 ppbv at 37 km are compared with the remote sensing and in‐situ measurements by other groups and with photochemical‐dynamical model calculations.
Spacecraft Ram cloud atom exchange and N2 LBH glow
Authors: Swenson G. R. , Meyerott R. E.
Published: February 2008

Recently a ram source of N2 Lyman‐BirgeHopfield (LBH) emission has been reported on S3‐4 satellite. An investigation of likely chemical processes responsible has identified a gas phase reaction involving ram atmosphere and the ram‐side cloud of gas leading the satellite. The process produces large quantities of fast N that impinge on low‐altitude spacecraft. Subsequent surface recombination produces excited N2 which results in the emission with predictions of altitude variation similar to that measured by other investigators.
Nighttime and daytime variation of atmospheric NO2 from ground‐based infrared measurements
Authors: Flaud J. ‐M. , Camy‐Peyret C. , Brault J. W. , Rinsland C. P. , Cariolle D.
Published: February 2008

During the period February 28 to March 2, 1986, 19 high resolution atmospheric spectra have been recorded during the night using the moon or during the day using the sun as a source with the Fourier transform spectrometer at the McMath Solar telescope on Kitt Peak. The NO2 absorption peak located at 2914.65 cm−1 has been used to derive from the spectra the total vertical column densities of atmospheric NO2. A rather rapid decrease of the NO2 amount during the night has been observed and its daytime increase from sunrise to sunset has been confirmed. A comparison with the predictions of a photochemical model is given.
Meteorite concentrations in Antarctica: Sites of Katabatic Wind Ablation?
Authors: Cresswell Richard G.
Published: February 2008

Blue ice fields on Antarctica have yielded over 10,000 fragments of extraterrestrial material, yet the mechanism for these concentrations remains enigmatic. Focus has been placed on the role of glaciological processes; I here propose that meteorological processes are also significant. Katabatic winds possess the necessary attributes to account for substantial sublimation of the ice in very localized zones. Recent studies indicate that these winds have distinct confluences along the coastal slopes of the Antarctic plateau. A tentative correlation of these with meteorite accumulations is suggested (Figure 1), though more year‐round surveillance of the local wind regimes is required before a working hypothesis can be proposed.
Seismic observation of a high‐velocity slab 1200–1600 km in depth
Authors: Vidale John E. , Garcia‐Gonzalez Douglas
Published: February 2008

A slablike high‐velocity region 1200–1600 km beneath the east coast of North America apparently has a half‐width of 450 km and a lateral extent of 3000 km and a depth extent of more than 800 km. This slab lies beneath the boundary where the Farallon Plate had been subducting for up to 120 MA. The high‐velocity anomaly has been inferred previously from travel‐time studies; this study uses body‐waveforms to verify and refine its structure. The anomalous region has a peak shear wave velocity 1.5% greater than the surrounding region and compressional velocity 0.6% greater. The width and smoothness of this anomaly is constrained by the complexity observed in SH waveforms from deep earthquakes beneath South America observed at GDSN stations in North America. This slab is about 5 times broader and 5 times weaker in its velocity anomaly than most slabs observed in the upper mantle. This observation implies that if this slab has passed through the 650 km discontinuity, which is the most likely explanation for the observation, it has been spread by more than simply thermal conductivity. The possibility that there is two‐layer convection with thermal coupling is not ruled out, however, as thermal coupling could lead to a similar pattern.
Inversion of regional Pn1 and surface‐wave data for source parameters of a Borah Peak aftershock
Authors: Patton Howard J. , Doser Diane I.
Published: February 2008

We present results of a comparative source study on one of the largest aftershocks of the Borah Peak, Idaho, earthquake series. The mechanism of this event had been previously studied using first motions and teleseismic p‐wave data, and we report here our results from analysis of regional Pn1 and surface waves. The Pn1 waves gave an estimate of the source duration near 5 sec, in agreement with the teleseismic p‐waves. Both the source duration and the effect of surface‐wave dispersion through laterally heterogeneous crustal structures must be accounted for in the moment‐tensor inversions of intermediate period surface waves. All data sources, both long period and short, gave consistent source mechanisms, and the long periods also yield three independent and consistent estimates of the seismic moment. The results demonstrate the promise of formal source‐parameter retrieval techniques applied to regional data for the study of earthquakes with magnitudes below the magnitude threshold of teleseismic source determinations.
A new class of natural magnetic materials: The ordering alloys
Authors: Wasilewski Peter
Published: February 2008

Tetrataenite (∼FeNi), found in many meteorites, and Josephinite (∼FeNi3), found in many serpentinized peridotites and possibly in Allende, a carbonaceous chondrite, are ordering alloys. Knowledge of thermomagnetic contrasts between the ordered and disordered states is of some practical importance since misinterpretation would be the consequence of failing to recognize them. Magnetic characteristics of the ordered state are recorded during heating to the apparent Curie point, which coincides with the Curie point of the disordered state. Magnetic characteristics of the disordered state are recorded during cooling from the “Curie point” to room temperature. The ordered alloys can be annealed in the vicinity of 500°C in order to monitor the kinetics of disordering, and to obtain a magnetization record characteristic of the state of order. In the ideal scenario, the minerals acquire thermoremanence (TRM) on cooling below the Curie point (∼550°C for FeNi and ∼610°C for FeNi3), and order below the ordering temperature (∼320°C for FeNi and ∼500°C for FeNi3). In natural circumstances, more likely, the appropriate alloy may form below the Curie point and above the ordering temperature and also near or below the ordering temperature. Induced magnetic anisotropy is characteristic of the ordered state, reaching the extreme for the tetragonal, truly uniaxial anisotropy in FeNi. At the present state of understanding, we can only speculate on what effect atomic ordering might have on the original remanence.
On the energy crisis in the Io plasma torus
Authors: Smith Robert A. , Bagenal Fran , Cheng Andrew F. , Strobel Darrell F.
Published: February 2008

Recent calculations of the energy balance of the Io plasma torus show that the observed UV and EUV radiation cannot be maintained solely via energy input by the ion pickup mechanism. Current theoretical models of the torus must be modified to include non‐local energy input. It is argued that the required energy may be supplied by inward diffusion of energetic heavy ions with energies less than about 20 keV.
High Schmidt numbers in the mesopause region from 224 MHZ incoherent backscatter
Authors: Hall Chris , Brekke Asgeir
Published: February 2008

Evidence for high Schmidt numbers at 224 MHz has been seen in incoherent backscatter from the mesopause region. Schmidt numbers in excess of around 2 indicate that the electron gas inner scale is no longer representative of the neutral atmosphere turbulence, an effect that could occur in the presence of heavy ions such as those associated with noctilucent clouds. In addition to examples of Schmidt number profiles, we present some tentative ion mass estimates, and explain how these may be used to deduce the hydration path of cluster ions.
Classical chaos in nonseparable wave propagation problems
Authors: Palmer David R. , Brown Michael G. , Tappert Frederick D. , Bezdek Hugo F.
Published: February 2008

Numerical calculations show that acoustic ray paths in a weakly range‐dependent deterministic ocean model exhibit chaotic behavior, that is, have an exponentially sensitive dependence on initial conditions. Since the ray equations define a nonautonomous Hamiltonian system with one degree of freedom, these results may be understood in terms of recent advances in classical chaos. The Hamiltonian structure of ray equations in general suggests that chaotic ray trajectories will be present in all types of linear wave motion in geophysics when variables do not separate, as in laterally inhomogeneous media.
Correlation diagrams in 40Ar/39Ar dating: Is there a correct choice?
Authors: Dalrymple G. Brent , Lanphere Marvin A. , Pringle Malcolm S.
Published: February 2008

Contrary to published assertions, the two types of correlation diagrams used in the interpretation of 40Ar/39Ar incremental‐heating data yield the same information provided the correct mathematics are used for estimating correlation coefficients and for the least squares fit. The choice is simply between two illustrative, graphical displays, neither of which is fundamentally superior to the other.
On the aspect ratio of Rayleigh‐Benard convection cells
Authors: Christensen Ulrich , Yuen David
Published: February 2008

We report numerical model calculations of isoviscous bottom‐heated convection in a two‐dimensional box with aspect ratio twelve. The aim was to determine the preferred aspect ratio of convection cells. Time‐dependent runs were started from two widely different initial conditions. At Rayleigh numbers in the range 105‐106 about eight cells with a mean aspect ratio of 1.5 formed eventually in each case. Thus neither the preference for approximately square cells, nor the stability of very elongated cells could be confirmed. The existence of large‐scale convective structures in the earth's mantle must be due to deviations from the simple Rayleigh‐Bénard model of convection.
Channel tortuosity variation in Florida triggered lightning
Authors: Idone Vincent P. , Orville Richard E.
Published: February 2008

We present the channel geometries and vertical profiles of tortuosity for five natural lightning flashes and seven triggered flashes photographed in Florida. The tortuosity variation with height was quantified using the tortuosity measurement method of Hill applied over successive 200 m vertical sections. Total channel lengths analyzed were between 1 km and 1.5 km. The triggered channels often show a significant reduction of tortuosity with height; the natural flashes show no apparent trend of tortuosity variation with height. A time‐resolved record of one of the triggered flashes reveals an abrupt doubling in speed of the upward leader associated with a sharp reduction in channel tortuosity. This observation suggests that positive lightning leaders may manifest decreased tortuosity when driven by larger fields.
Evidence of quasi‐biennial oscillations in a general circulation model
Authors: Currie Robert G. , Hameed Sultan
Published: February 2008

Pulses with periods of nearly two years are known to influence weather and climate. The underlying mechanism of this phenomenon has remained elusive. In this report we show that the time series of air temperature, air pressure, and ocean temperature calculated in a coupled ocean‐atmosphere general circulation model display quasi‐biennial oscillations. The amplitude of the oscillation generally increases with latitude although its magnitude relative to the annual cycle decreases with latitude. The general circulation model we have studied does not incorporate the tropical stratosphere; this implies that tropospheric quasi‐biennial oscillations originate within the troposphere‐ocean system.
A 3500‐year paleomagnetic record of Late Holocene secular variation from Blue Lake, Idaho
Authors: Hanna Ruth L. , Verosub Kenneth L.
Published: February 2008

Three meters of sediment from Blue Lake, Idaho, have provided a 3500‐year paleomagnetic record with low scatter and good serial correlation. Comparison of the Blue Lake record with the record from Fish Lake, Oregon, reveals differences of up to 963 years for secular variation extrema based on the separate radiocarbon chronologies for Blue Lake and Fish Lake. To achieve a common time scale, the Blue Lake record was redated using the Fish Lake ages for five major inclination extrema. With this adjusted time scale, the excellent correspondence between the declination records confirms the extremal correlations and demonstrates that paleomagnetic correlations may provide more accuracy for relative stratigraphy than radiocarbon dating. The morphological agreement between the smoothed records documents secular variation features with wavelengths of 1000‐2000 years and amplitudes of 10°‐20° in inclination and 20°‐30° in declination. Examination of the unsmoothed records indicates that features with wavelengths of less than a few hundred years and amplitudes of less than 5° are probably noise.
Self‐excitation of auroral arcs in a three‐dimensionally coupled magnetosphere‐ionosphere system
Authors: Watanabe Kunihiko , Sato Tetsuya
Published: February 2008

This paper presents the first full three‐dimensional dynamic simulation of auroral arc formation. The magnetospheric and ionospheric dynamics are represented by one‐fluid magnetohydrodynamic equations and two‐fluid weakly ionized plasma equations, respectively. The feedback coupling between magnetospheric Alfven waves and ionospheric density waves results in a spontaneous generation of longitudinally elongated striations of field‐aligned currents and ionospheric electron densities, which compare very well with many features of quiet auroral arcs.
Tropospheric response to tropical diurnal forcing observed by Meteosat
Authors: Duvel Jean Philippe , Kandel Robert S.
Published: February 2008

Climatological diurnal variations of atmospheric physical properties are well known, particularly in the tropics. We have analyzed Meteosat data obtained every 3 hours during 3 summers (JJA 1983‐85) in the "water‐vapor" (WV, 6.5 µm) band which depends on temperature and humidity in layers above 500 millibars. We find that spatially coherent diurnal variations of a few percent appear to extend well beyond the regions of convection into cloud‐free areas. Furthermore, we observe propagation of a diurnal pulse in the WV signal, eastward and westward from the land areas of deep convection. We discuss the mechanisms that may be involved and conclude that we are observing the forced reponse of the middle and upper troposphere to the diurnally pulsating release of latent heat above central Africa and South America.
Estimation of the attenuation operator for multiple‐ScS waves using digitally recorded broadband data
Authors: Sipkin Stuart A.
Published: February 2008

Broadband multiple‐ScS waveforms have been obtained for several deep‐focus earthquakes in the Izu‐Okhotsk region from the intermediate‐period channels of the RSTN network. Differential travel times have been computed by waveform cross‐correlation. Estimates of the multiple‐ScS attenuation operator have been obtained using a phase‐equalization and stacking technique. For this mixed, but mostly tectonic path crossing the eastern margin of Asia and northwestern North America we obtain a median ScSn‐ ScSn−1 travel time residual of +0.6s with respect to the J‐B velocity model and a QScS of 182±21 over the frequency band 0.017‐0.117Hz. In this band there is no apparent frequency dependence. We find that the Aleutian back‐arc region and central Alaska is slower and has a higher attenuation than the rest of the path. Even though the data contain much higher frequencies, beyond ∼0.117 Hz the multiple‐ScS phases lose coherence and the results become unstable.
Comment on “Interplanetary protons (EP ≈ 1 MeV) 1973‐1986 and out to 22.4 AU”
Authors: Feynman Joan
Published: February 2008

Van Allen and Decker (1988) have drawn attention to the anomalous behavior of several solar and interplanetary phenomena in 1980 and suggested the anomalies are caused by the reversal of the solar polar magnetic field polarity. However, I show anomalous behavior of geomagnetic activity in that year that could not have been due to any event associated with all solar maximums. I suggest the 1980 anomaly may be connected with the declining phase of the 88 year cycle of the sun and solar terrestrial relations.
Two‐dimensional modelling of the Antarctic lower stratosphere
Authors: Chipperfield M. P. , Pyle J. A.
Published: February 2008

We have used a two‐dimensional radiative‐dynamical‐chemical model to study some aspects of Antarctic ozone depletion. While many aspects of the preconditioning of the vortex are reproduced by simply reducing the horizontal diffusion during the Antarctic winter and early spring, significant problems remain. The lack of knowledge of the meridional circulation throughout the year represents a serious limitation.

When a springtime ozone depletion is imposed on the model in the Antarctic, the effect of the depletion is confined mainly to high southern latitudes. The consequent changes in radiative transfer lead to lower temperatures in the lower polar atmosphere during spring, with some smaller increases in temperature above about 20mb.
Stratospheric NO2 column measurements from three Antarctic sites
Authors: Keys J. G. , Johnston P. V.
Published: February 2008

Ground‐based measurements of stratospheric NO2 made from three Antarctic sites in 1986 and 1987 show the effect on the NO2 column at each station of photochemical changes brought about by changing season, superimposed on the dynamically induced intrusion of lower latitude NO2 enriched air. At the special location of South Pole station, NO2 slant column changes can be observed at effectively constant solar zenith angle, and show the effects of a horizontal gradient in the NO2 distribution.
Total ozone by lunar Dobson observation at Syowa, Antarctica
Authors: Chubachi Shigeru , Kajiwara Ryoichi
Published: February 2008

In this paper, the accuracy of total ozone measurements by lunar Dobson observation at Syowa, Antarctica is discussed. The changes in total ozone and vertical ozone profiles before and after January 1982 are also described.
Relation of Antarctic 100 mb temperature and total ozone to equatorial QBO, equatorial SST, and sunspot number, 1958‐87
Authors: Angell J. K.
Published: February 2008

Year‐to‐year changes in springtime (September‐October‐November or SON) values of Antarctic 100 mb temperature and total ozone have been compared with each other and with year‐to‐year changes in SON values of equatorial 50 mb temperature (reflecting the quasi‐biennial oscillation or QBO) and sea‐surface temperature (SST) in eastern equatorial Pacific (reflecting El Nino). During the 30‐year period 1958‐87, there has been a significant (at the 5% level) correlation of 0.73 between year‐to‐year changes in SON values of Antarctic 100 mb temperature and total ozone, as well as a significant correlation of −0.64 between year‐to‐year changes in SON values of Antarctic 100 mb temperature and equatorial 50 mb temperature. There has been little correlation (−0.18) between year‐to‐year changes in Antarctic 100 mb temperature and SST in eastern equatorial Pacific. However, year‐to‐year changes in Antarctic total ozone have been almost equally related to year‐to‐year changes in equatorial 50 mb temperature and equatorial SST (respective correlations of −0.44 and −0.42), with a significant correlation of −0.60 if the latter two quantities are considered jointly (multiple correlation). Unlike the Arctic in winter, there is no evidence of an increase in springtime values of Antarctic 100 mb temperature (and total ozone) with increase in sunspot number when the equatorial QBO is in the west‐wind phase, but there is provisional evidence of such an increase in the east‐wind phase.
Radiative aspects of the Antarctic ozone hole in 1985
Authors: Akiyoshi Hideharu , Fujiwara Motowo , Uryu Michiya
Published: February 2008

In order to investigate the radiative heating effects of aerosols during September‐October, 1985, in Antarctica, we have solved the radiative transfer equation using a one‐dimensional model, which includes the absorption of solar energy, the thermal emission and absorption, Rayleigh and Mie scattering, and the surface scattering effects. Our calculations are based on the SAGE II data. The results show that the Antarctic stratosphere was nearly in radiative equilibrium during that period, if the effects of aerosols are excluded. It is also shown that the heating effects of aerosols are too small to cause effective upward motions, although some ambiguous parameters such as the aerosol composition and the size distribution are chosen so that they magnify the effects.
Characteristics of basement rocks exposed near the Cajon Pass Scientific Drill Hole
Authors: Ehlig Perry L.
Published: February 2008

Basement rocks exposed near the drill site to the northeast of the San Andreas fault consist of Mesozoic granitoid intrusions and amphibolite facies migmatitic gneiss. A possible tongue or lobe‐shaped pluton of granodiorite is exposed on Cleghorn Ridge, Squaw Peak and Whale Mountain. Adjacent gneiss contains marble, calcsilicate rocks, quartzite, and aluminous schist of sedimentary origin. Metagabbro and dioritic gneiss of possible igneous origin are also present. Peak metamorphic temperatures during emplacement of granodiorite are estimated to have been between 600 to 750°C at a pressure between 3‐6 kb.
Petrological and geochemical investigations at the Cajon Pass Deep Drillhole
Authors: Silver Leon T. , James Eric W. , Chappell Bruce W.
Published: February 2008

Chemical analyses of cores from the Cajon Pass Deep Drillhole confirm vertical lithologic diversity of the basement rocks. They are metaluminous and calcalkaline; weak major element correlations with wide‐ranging SiO2 suggest they are not a simple cogenetic suite. Quartz contents correlate with the thermal gradient profile, supporting conduction as the principal thermal transport mechanism. Abundances of heat producing elements are variable and somewhat lower than average crustal values. Cross‐calibration with other measures of Th, U and K are underway. Ages of surface granitoids and core 17 are late Cretaceous; other plutonic rocks appear older but late Mesozoic. Initial lead isotopic signatures of the plutonic rocks change dramatically with depth in the hole.
In situ investigations of thermal conductivity, heat production, and past hydrothermal circulation in the Cajon Pass Scientific Drillhole, California
Authors: Williams Colin F. , Anderson Roger N. , Broglia Cristina
Published: February 2008

Wireline logs from the Cajon Pass drillhole provide observations of crustal properties and processes near the San Andreas fault. Mineralogical profiles developed from geochemical logs are combined with a technique for calculating thermal conductivity from the volume fractions of component minerals. Variations in the equilibrium temperature gradient correlate with conductivity contrasts, and thus with lithology, rather than with fluid circulation. K, U, and Th contents calculated from gamma spectroscopy logs yield heat production values which range from 1.3 to 2.4 µW/m³, averaging 1.8 µW/m³ in the section from 500 to 1800 m. Evidence for depletion of U relative to Th raises the possibility of extensive fluid circulation in the past. However, discontinuity of depletion across faults suggests that the fluid regime responsible for U depletion predated San Andreas faulting.
In situ stress orientation near the San Andreas Fault: Preliminary results to 2.1 km depth from the Cajon Pass Scientific Drillhole
Authors: Shamir Gadi , Zoback Mark D. , Barton Colleen A.
Published: February 2008

Stress‐induced wellbore breakouts were analyzed in the Cajon Pass Scientific Drillhole (4.3km NE of the San Andreas fault) to determine the orientation of the principal horizontal stresses, using borehole televiewer digitized data. In the depth interval 1750‐2115 m the mean orientation of the maximum horizontal stress is 073°. The scatter in the orientation of breakouts is as much as ±37°, and variations occur with wavelengths of few hundred meters in this interval, reflecting either true changes in stress orientation with depth or the variability of rock anisotropy. All the measured orientations, however, result in left‐lateral shear stress resolved onto planes parallel to the San Andreas fault, contrary to its post Miocene right‐lateral slip of ∼ 300 km. The stress orientation is consistent, however, with reported left lateral displacement across the Cleghorn fault (3 km northeast of, and possibly subparallel to the San Andreas near Cajon Pass) since the Pleistocene. The Cajon Pass stress orientation may reflect the current state of stress across the San Andreas fault, in which case it should change prior to right lateral slip on this fault, or a shallow local perturbation to the San Andreas stress field, in which case it should rotate couterclockwise with depth. Determination of the stress orientations at greater depths in the Cajon Pass drillhole will better sample the near field of the San Andreas fault and help resolve this question.
Multiply‐polarized shear‐wave VSPs from the Cajon Pass Drillhole
Authors: Daley T. M. , McEvilly T. V. , Majer E. L.
Published: February 2008

A 3‐component VSP data set was acquired in the Cajon Pass Drillhole, with a multiply‐polarized shear‐wave source and a conventional P‐wave source, producing a 9‐component data set. The VSP data show effects on the full wavefield from the sediment‐granite interface. Mode‐converted waves are identified, with significant scattering of S‐wave energy from the leading P‐wavefront. Hodographs are used to display S‐wave particle motions in two dimensions. Shear‐wave splitting is observed in the hodographs. The shear‐wave particle motion is used to infer anisotropy orientation with respect to the local strike of the San Andreas fault. Stress‐induced fracturing is assumed to be a possible cause of the shear‐wave splitting. A variation of particle motion orientation with depth is observed, implying a variation in anisotropy orientation as a function of depth.
Predicted variation of stress orientation with depth near an active fault: Application to the Cajon Pass Scientific Drillhole, southern California
Authors: Wesson Robert L.
Published: February 2008

Preliminary measurements of the stress orientation at a depth of 2 km in the Cajon Pass Scientific Drillhole, about 3.6 km from the San Andreas fault in southern California, indicate that the local direction of maximum compression is nearly normal to the fault zone. The measurements have been interpreted to indicate that the regional orientation of the maximum compression is normal to the fault, and taken as evidence for a very weak fault. The orientation of the regional maximum compression expected from plate tectonic arguments is about 66° NE from the strike of the fault. Geodetic data indicate that the orientation of maximum compressive strain rate is about 43° NE from the strike of the fault, and show nearly pure right‐lateral shear acting parallel to the fault. These apparent conflicts in the inferred orientation of the axis of maximum compression may be explained in part by a model in which the fault zone is locked over a depth interval in the range of 2‐5 to 15 km, but is very weak above and below that interval. An analytic solution for this model predicts orientations of the principal stresses that are nearly parallel or normal to the fault, for observations made close to the fault and above and below the locked zone, but an orientation consistent with plate tectonic estimates at depths corresponding to that of the locked interval. This solution does require, however, a few mm/yr of creep at the surface on the San Andreas or nearby sub‐parallel faults (such as the San Jacinto), which has not yet been observed, or a shallow zone near the faults of distributed deformation.
Analysis of macroscopic fractures in the Cajon Pass Scientific Drillhole: Over the interval 1829‐2115 meters
Authors: Barton Colleen A. , Moos Daniel
Published: February 2008

The orientation, distribution and apparent aperture of natural fractures intersecting the Cajon Pass research well were determined through analysis of borehole televiewer (BHTV) data over the interval 1829 to 2115 meters. Large open fractures have shallow inclinations and tend to be aligned striking roughly N15°E. There is no apparent relationship between these fractures and the current stress state, as measured by the analysis of wellbore breakouts and hydraulic fracturing experiments in the Cajon Pass well and as observed in other studies in the region. Temperature anomalies due to fluid flow into the well detected during a long‐term permeability experiment occur at several of these fractures. Compressional, shear and Stoneley guided wave velocities are within the expected range for crystalline rocks and elastic‐wave anomalies are associated with the larger fractures. Stoneley wave coherence is reduced where the fractures are hydraulically conductive.
Fracture distribution and basement structure from measurements of electrical resistivity in the basement of the Cajon Pass Scientific Drillhole, California
Authors: Pezard Philippe A. , Anderson Roger N. , Howard James J. , Luthi Stefan M.
Published: February 2008

In‐situ deep and shallow measurements of electrical resistivity recorded with the Dual Laterolog in the basement of the Cajon Pass scientific drillhole are compared with laboratory measurements of resistivity and porosity on fracture‐free core samples. This comparison is the basis of a simple electrical model of the pore space of the rock from which both matrix and fracture porosity are derived. In parallel, the analysis of borehole electrical images obtained with the Formation Microscanner provides a means to identify the fractures that intersect the borehole wall, to evaluate their frequency, and to determine their orientation. Further processing of these images enables us to distinguish mineralized from fluid‐filled fractures. The comparison of laterolog‐derived fracture porosity, computed over a large volume of rock, with a pair of fracture intensity profiles obtained from the analysis of the two images of the borehole wall is the key of a new technique by which drillhole‐related fractures (either due to hydraulic fracturing or to stress‐induced borehole breakouts) and natural fractures (either open or mineralized) are discriminated. The fractures in the upper part of Cajon Pass basement are inferred from the analysis of in‐situ resistivity measurements as mostly steep and mineralized.
The effects of mylonitization and fractures on elastic wave velocities in crystalline rock — Examples from the Cajon Pass Scientific Drillhole
Authors: Moos Daniel
Published: February 2008

Sonic compressional and shear wave velocities were calculated from full waveforms recorded in the Cajon Pass drillhole from 250 to 1829 m depth. A complete suite of Schlumberger logs was also recorded over the same interval. Compressional velocities in the sediments (250‐495 m) range from 3.3 to 4.0 km/s; shear velocities are unreliable. Shallow crystalline basement has low velocities (Vp < 4.8; Vs < 2.8 km/s) and resistivities due to minor alteration. Below 708 m Vp is 5.5 to 6.0 km/s and Vs is 3.2 to 3.5 km/s. Velocities are generally lower in more felsic rocks. In gneisses sonic waveforms are more distorted, semblance coherence is lower and physical properties are more variable. Mylonitized zones and fractured intervals have distinctly lower velocities but different aggregate log response. Lower velocities are found within a zone of fractures within the gneiss at about 840 m. Porosity increases only at one large fracture within the interval. In a mylonitized shear zone at 1440 m the velocity reduction and the porosity increase occur across the zone.
Acquisition and preliminary analysis of oriented multi‐component multioffset VSP data: DOSECC Cajon Pass Deep Scientific Drillhole
Authors: Rector James W.
Published: February 2008

In October 1987 a four‐offset VSP (Vertical Seismic Profile) was acquired at the Cajon Pass Deep Scientific Drillhole. Preliminary velocity analysis of the P‐wave direct arrival has identified zones in the upper crystalline section of the borehole where interval velocities derived from a long‐spaced sonic log differ greatly from the VSP interval velocities. Large velocity differences were observed between the three near‐offset VSPs in the upper crystalline section of the borehole. These differences are interpreted as being associated with the complex geologic structure near the Cajon Pass borehole. Two source positions, one 35 m from the borehole and one 346 m from the borehole were used to analyze the horizontal component holograms of the P‐wave direct‐arrival. The near‐offset hodograms exhibited particle motion directions which were not coincident with the VSP source direction when the downhole receiver was in crystalline rock. The far‐offset hodograms exhibited particle motion directions which were generally consistent with the source direction.
Paleomagnetic results from granitic basement rocks in the Cajon Pass Scientific Drillhole
Authors: McWilliams Michael , Pinto Michael J.
Published: February 2008

Natural remanent magnetizations in granitic rocks intersected by the Cajon Pass scientific drillhole are a composite of two superimposed magnetizations. One magnetization is a primary TRM acquired in late Cretaceous times upon initial cooling, while the other is an IRM induced by the coring device. Coring‐induced IRM has obscured any pre‐coring VRM, and thus core orientation using recent VRM was not possible. Primary inclinations are internally consistent and agree with expected values derived from the adjacent Sierra Nevada and Southern California batholiths.
Heat flow and thermal structure of the Washington‐Oregon accretionary prism—A study of the lower slope
Authors: Shi Yaolin , Wang Chi‐yuen , Langseth Marcus G. , Hobart Michael , von Huene Roland
Published: February 2008

Heat flow measurements across the Washington‐Oregon convergent margin show several characteristic features: a well defined peak at the foot of the overthrust, a gradual decrease landward across the lower slope reaching a minimum at the ridge, and a gradual rise further landward. Constrained by geological and seismic evidence on the rate of stacking and the dimension of stacked thrust sheets and by drilling results on sediment properties, we use a two‐dimensional time‐dependent finite element procedure to model the stacking of overthrust slices of sediments and to calculate the thermal structure beneath the lower slope of the accretionary prism; the calculated heat flow profile is in good agreement with the measurements. Advective heat transfer due to stacking of overthrust sheets and topographic changes are shown to play a dominant role in controlling the surface heat flow and the thermal state of the accretionary prism.
An assessment of the long‐term drift in TOMS total ozone data, based on comparison with the Dobson Network
Authors: Fleig Albert J. , Silberstein David S. , Wellemeyer Charles G. , Cebula Richard P. , Bhartia Pawan K.
Published: February 2008

Using techniques very similar to those used in comparing SBUV total ozone with Dobson [Fleig et al. 1986A], seven years of total ozone data derived from the TOMS instrument on Nimbus‐7 are compared with results from 41 Dobson stations. In this study however, a significant improvement in fit is obtained using a model which assumes a change in the rate of drift between TOMS and Dobson around the middle of 1982. Results indicate that the TOMS measurements have drifted relative to the Dobson stations with a two‐part linear trend of −0.25 ± 0.17 % per year during the period from launch to 6/30/82, and −0.51 ± 0.21 % per year during 7/1/82 ‐ 10/31/85. As discussed in Fleig et al. [1986A], we are not yet able to definitively separate the causes of this drift between residual uncorrected drift in the TOMS instrument (a similar drift is apparent in the SBUV‐Dobson comparisons), limited sensitivity of the TOMS to increases in tropospheric ozone, and the effect of local increases in pollution levels on individual Dobson stations.