bluuebunny/crossref_metadata_2025 huggingface dataset:
Night‐time peroxy radical chemistry in the remote marine boundary layer over the Southern Ocean
Authors: Monks Paul S. , Carpenter Lucy J. , Penkett Smart A. , Ayers Gregory P.
Published: February 2004

Peroxy radical measurements were made in the remote marine boundary layer over the Southern Ocean at Cape Grim, Tasmania during January and February 1995. From the experimental peroxy radical data it is clearly demonstrated that there is little night‐time oxidation chemistry taking place. In such an environment at night the sole type of peroxy radical that persists is CH3O2 (τ > 12 hours) and the only nocturnal chemical process involving peroxy radicals appear to be the self‐reaction of CH3O2 coupled to either a small but finite deposition velocity (kd ∼ 0.003 m s−1) or a slow reaction with O3 (k(CH3O2 + O3)≤8 × 10−18 cm³ molecule−1 s−1). A deviation between experimentally determined peroxy radical levels and J(O¹D) in the late afternoon is discussed and modelled in terms of the peroxy radical self‐reactions.
Upper atmosphere Ca and Ca+ at mid‐latitudes: First simultaneous and common‐volume lidar observations
Authors: Alpers Matthias , Höfffner Josef , von Zahn Ulf
Published: February 2004

We report on simultaneous, common‐volume observations of Ca and Ca+ layers in the 80 to 125 km altitude range by groundbased resonance lidar. The measurements were carried out during 9 nights in summer 1995 on the German island Rügen (55°N, 13°). We observed a permanent Ca layer with an average peak density of 31 atoms/cm³ at 87 km altitude. The average Ca column abundance was 2.2×107 cm;−2. No permanent Ca+ layer was found, but sporadic Ca+ layers occured frequently in the altitude range 90–120 km. Peak densities of these thin layers varied between 65 and 3900 atoms/cm³. We demonstrate the interesting possibilities of groundbased simultaneous common‐volume observations of neutral and ionized calcium in the lower thermosphere.
Coordinated measurements of auroral light intensities and Riometric radio‐wave absorption
Authors: Stoker P. H. , Mathews M. J. , Scourfield M. W. J.
Published: February 2004

Digitized allsky images of auroral optical emissions, recorded by a low light level TV system at Sanae (70.3°S, 2.4°W, L=4.0), have been mapped onto the angular sensitivity functions of both a broad, single‐beam riometer and narrow beams of an imaging riometer. During the rising phase of a substorm before local magnetic midnight, on 11 May, 1992, the integrated optical intensities in the inner four beam directions of the 16‐beam imaging riometer followed each other fairly closely, while the absorptions showed marked spatially inhomogeneous distributions. Regions of ionospheric absorption appeared not to coincide spatially with regions of discrete optical structures, but were adjacent to these structures. A small step of ∼0.09 dB in absorption was observed shortly after onset of the substorm on 27 July, 1979, and again on 11 May, 1992, but before the sharp increase in absorption. This step in absorption may be due to highly enhanced E‐region electron temperatures arising from strong dc electric fields connected to auroral arcs. During the event of 9 June, 1991, which started with an SSC at 00:40 UT, enhancements in absorptions followed enhancements in optical emissions repeatedly after 52 s.
Nonlinear evolution of interplanetary Alfvénic fluctuations with convected structures
Authors: Roberts D. Aaron , Ghosh Sanjoy , Goldstein Melvyn
Published: February 2004

At least at solar minimum, many regions in slow solar wind near the heliospheric current sheet have very low Alfvénicity. Motivated by recent suggestions that the interaction of the waves with the observed striated density, temperature, and magnetic field structures in the low Alfvénicity regions causes the decay of outward dominance, we have used two‐ and three‐dimensional MHD codes to simulate such situations to determine the evolution. We find that outward propagating waves in the presence of structures become only slightly less Alfvénic (unlike observations), and that what were initially parallel propagating waves fairly rapidly become nearly isotropic with a self‐similar spectrum typical of turbulence (similar to observations). These simulations suggest that the low Aflvénicty regions must arise from some other cause, such as “microstreams” that are eradicated as they decrease the Alfvénic correlations.
Oscillations in polar mesospheric summer echoes and bifurcation of noctilucent cloud formation
Authors: Sugiyama Takuya , Muraoka Yoshikazu , Sogawa Hisato , Fukao Shoichiro
Published: February 2004

Oscillations having periods of 5.5 days are found in polar mesospheric summer echoes (PMSEs) observed during 1980 to 1984 with the MST radar at Poker Flat, Alaska. Simulations of noctilucent cloud (NLC) formation are made in the case that embryos for cloud ice particles are proton‐hydrates H+(H2O)n (PHs). Results show that cloud formation bifurcates from a stably steady structure into a quasi‐steady and a stably oscillatory structure in accordance with an increase of humidity. By capturing electrons, descending crowds of ice particles may cause PMSEs. The cyclic behavior of PMSEs is considered to be an indication of the in situ origin of NLCs.
Infrared spectra of phase B at high pressures: Hydroxyl bonding under compression
Authors: Faust J. , Williams Q.
Published: February 2004

Phase B synthesized from a natural peridotite has been studied to 30.5 (±1.5) GPa on compression and decompression using infrared spectroscopy. The mode shifts of the OH1 (3345 cm−1) and the OH2 (3404 cm−1) vibrations of phase B are extremely small, −0.8 cm−1/GPa and 0.9 cm−1/Gpa, respectively, indicating that the hydrogen bonding in this phase is extremely insensitive to pressure. The opposite signs of the two mode shifts indicate that the OH1 hydrogen bond becomes stronger on compression, while the OH2 hydrogen bond weakens. Because both hydroxyl units are hydrogen bound to the same oxygen, this behavior may reflect hydrogen‐hydrogen repulsion in these sites as the lattice undergoes pressure induced compaction. Our results indicate that the environment surrounding the hydroxyl units in this phase is significantly more rigid than that present in a range of other hydrous magnesian silicate phases. Systematics of vibrational spectra among hydrous phases in the MgO‐SiO2‐H2O system indicate that pressure enhances hydrogen bonding through polymorphic transitions; yet, as illustrated by our results, the effect of pressure on hydrogen bonding within any single phase is small. Therefore, variations in hydrogen bonding may play a primary role in the notable polymorphism of hydrous phases at high pressures.
A study of the composition and energy spectra of anomalous cosmic rays using the geomagnetic field
Authors: Mewaldt R. A. , Cummings J. R. , Leske R. A. , Selesnick R. S. , Stone E. C. , von Rosenvinge T. T.
Published: February 2004

We use instrumentation on SAMPEX and the Earth's field as a magnetic rigidity filter in a “double spectrometer” approach to measure the composition and energy spectra of anomalous cosmic rays (ACRs) with Z≥6. A “pure” sample of anomalous cosmic ray C, N, O, and Ne is obtained, with no significant evidence for other species. The bulk of ACRs are now known to be singly‐charged, and the geomagnetic filter allows their energy spectra to be measured to higher energies than before. The anomalous oxygen spectrum is found to extend to at least ∼100 MeV/nuc, which has implications for models of the acceleration of these ions.
Dual‐frequency interferometric SAR observations of a tropical rain‐forest
Authors: Rignot E.
Published: February 2004

Repeat‐pass, interferometric, radar observations of tropical rain‐forest collected by the Shuttle Imaging Radar C (SIR‐C) in the state of Rondonia, Brazil, reveal signal coherence is destroyed at C‐band (5.6‐cm) in the forest, whereas L‐band (24‐cm) radar signals remain strongly coherent over the entire landscape. At L‐band, the rms difference in inferred topographic height between the forest and adjacent clearings is 5 m, equivalent to the height noise. Atmospheric delays are large, however, forming kilometer‐sized anomalies with a 1.2‐cm rms one way. Radar interferometric studies of the humid tropics must therefore be conducted at long radar wavelengths, with kilometric baselines or with two antennas operating simultaneously.
The 22‐Yr modulation of galactic cosmic rays and its relation to coronal holes
Authors: Bravo S. , Cruz‐Abeyro J. A. L.
Published: February 2004

We studied the relation between the long‐term temporal evolution of galactic cosmic ray (GCR) intensity observed in neutron monitors at Earth‐which shows alternating peaks of different shape depending on the polarity of the general solar magnetic field‐, and the evolution of the solar coronal holes for the period 1967–1988. This period covers almost one complete solar magnetic (22‐yr) cycle. We found that GCR intensity correlates with the evolution of the size of polar coronal holes, which also exhibits alternating time profiles in positive and negative phases of the solar magnetic cycle.
A note on evaluating VAN earthquake predictions
Authors: Tselentis G‐Akis , Melis Nicos S.
Published: February 2004

The evaluation of the success level of an earthquake prediction method should not be based on approaches that apply generalized strict statistical laws and avoid the specific nature of the earthquake phenomenon. Fault rupture processes cannot be compared to gambling processes. The outcome of the present note is that even an ideal earthquake prediction method is still shown to be a matter of a “chancy” association between precursors and earthquakes if we apply the same procedure proposed by Mulargia and Gasperini [1992] in evaluating VAN earthquake predictions. Each individual VAN prediction has to be evaluated separately, taking always into account the specific circumstances and information available. The success level of epicenter prediction should depend on the earthquake magnitude, and magnitude and time predictions may depend on earthquake clustering and the tectonic regime respectively.
Kinetic temperature ratios of O6+ and He2+: Observations from Wind/MASS and Ulysses/SWICS
Authors: Cohen C. M. S. , Collier M. R. , Hamilton D. C. , Gloeckler G. , Sheldon R. B. , von Steiger R. , Wilken B.
Published: February 2004

We present results from a two spacecraft study of the ratio of O6+ and He2+ kinetic temperatures as a function of solar wind speed. Data from the Wind/MASS and Ulysses/SWICS instruments both indicate the O6+/He2+ kinetic temperature ratio increases with increasing solar wind speed, peaking near 500 km/s. Above 500 km/s, the ratio appears to decrease slightly. Values near unity were obtained for slow solar wind while fast wind yielded ratios substantially higher than what is expected from the general rule Although averaging over all data would result in the nominal ratio of 4, deviations from equation (1) appear to be common and the assumption of equal thermal velocities should not be made a priori.
δ18O of atmospheric oxygen measured on the GRIP Ice Core Document Stratigraphic disturbances in the lowest 10% of the core
Authors: Fuchs Andreas , Leuenberger Markus C.
Published: February 2004

δ18O measured on oxygen in the bubble air from ice cores is a proxy for continental ice volume and is used to synchronize cores from Greenland and Antarctica. A record measured on ice samples from the Central Greenland deep ice core GRIP, spanning the Last Glacial Maximum and the Holocene, shows that δ18O of atmospheric oxygen lags δ18O of ice by about 4000 to 1000 years. The smooth isotope record of atmospheric oxygen shows a steady ice sheet decay beginning around 18′000 years BP taking the time lag into account. However, measurements performed on ice from the GRIP core older than 100 kyrs do not correlate with the corresponding Vostok record and show transitions too fast to be typical for ice sheet build‐up or decay. Furthermore, the expected time lag between δ18Oatm and δ18O of seawater or δ18O of ice is absent or has even turned into a lead. Climatic interpretation of the fast δ18Oice transitions is not consistent with our δ18Oatm results. The stratigraphy is possibly irregular and if so, this stops us from constructing a steady age‐depth relation in the deepest part of the GRIP ice core.
Travel‐time residuals of teleseismic P‐waves at the Rodriguez Triple Junction in the Indian Ocean using ocean‐bottom seismometers
Authors: Sato Toshinori , Katsumata Kei , Kasahara Junzo , Hirata Naoshi , Hino Ryota , Takahashi Narumi , Sekine Mayumi , Miura Seiichi , Koresawa Sadayuki
Published: February 2004

We conducted three weeks of seismic observations at the Rodriguez Triple Junction (RTJ) in the Indian Ocean using 18 ocean‐bottom seismometers over an area of 90km × 90km. We identified six teleseismic events and obtained significant anomalies in the relative travel‐time residuals of the teleseismic P‐waves. The residuals are positive at the RTJ, the northern part of the Southeast Indian Ridge (SEIR), and the eastern side of the Central Indian Ridge (CIR), and are negative at and around the Southwest Indian Ridge (SWIR). It is suggested that there is a relatively hotter mantle under the triple junction and the northern part of the SEIR segment, along‐axis variations in mantle temperature along the SEIR segment, and cooler mantle under the SWIR segment. The CIR segment has an asymmetrical distribution of relative residuals.
Spreading and intermittent structure of the upstream boundary of planetary magnetic foreshocks
Authors: Zimbardo G. , Veltri P.
Published: February 2004

The fast particles in the electron foreshocks propagate along the magnetic field lines, so that the effect of low frequency magnetic fluctuations is to create both a broadening and a fine structure of the foreshock upstream boundary. This is studied by means of a 3‐D numerical simulation of turbulent magnetic fields. Applications to Venus, Earth, and Mars magnetic foreshocks are done. It is found that a spacecraft can be magnetically connected to the bow shock even when it is upstream of the nominal magnetic foreshock boundary, and that the mixing of magnetic field lines can give an explanation for the broadband bursty electrostatic noise observed within the electron foreshock.
Trace gas transport in the Arctic Vortex inferred from ATMOS ATLAS‐2 observations during April 1993
Authors: Abrams M. C. , Manney G. L. , Gunson M. R. , Abbas M. M. , Chang A. Y. , Goldman A. , Irion F. W. , Michelsen H. A. , Newchurch M. J. , Rinsland C. P. , Salawitch R. J. , Stiller G. P. , Zander R.
Published: February 2004

Measurements of the long‐lived tracers CH4, N2O, and HF from the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument during the Atmospheric Laboratory for Science and Applications‐2 (ATLAS‐2) Space Shuttle mission in April 1993 are used to infer average winter descent rates ranging from 0.8 km/month at 20 km to 3.2 km/month at 40 km in the Arctic polar vortex during the 1992–93 winter. Descent rates in the mid‐stratosphere are similar to those deduced for the Antarctic vortex using ATMOS/ATLAS‐3 measurements in November 1994, but the shorter time period of descent in the Arctic leads to smaller total distances of descent. Strong horizontal gradients observed along the vortex edge indicate that the Arctic vortex remains a significant barrier to transport at least until mid‐April in the lower to middle stratosphere.
Fracture‐induced hydrothermal convection in the oceanic crust and the interpretation of heat‐flow data
Authors: Yang Jianwen , Edwards R. N. , Molson John W. , Sudicky E. A.
Published: February 2004

Small‐scale seafloor heat‐flow variations with a characteristic wavelength of about 1200 m have been observed on a profile over a sediment‐sealed ridge flank. Two theories have been advanced to explain them‐low aspect ratio hydrothermal convection in a highly permeable basement layer 600 m thick or high aspect ratio convection in an anisotropic permeable layer 200 m thick, induced by 20 m topographic variations with a 1000 m half wavelength. Neither theory is totally satisfactory. The first requires a very thick highly permeable zone while the absence of any resolvable basement relief on a complementary seismic survey limits the credibility of the second.

We hypothesize that sub‐critical hydrothermal convection in normal upper oceanic crust, driven by discrete fractures, can cause the observed heat flow anomalies. We test the hypothesis by using a finite‐element code to solve the coupled time‐dependent heat transport and fluid flow differential equations. Discrete fractures are incorporated explicitly. We show that the inclusion of fractures in layers 2A and 2B promotes convection. Fluid flow through fractures causes horizontal thermal gradients, and initiates and maintains sub‐critical convection within the upper basalts. The predicted heat flow variations are comparable with the observed data.
Stratospheric chlorine partitioning: Constraints from shuttle‐borne measurements of [HCl], [ClNO3], and [ClO]
Authors: Michelsen H. A. , Salawitch R. J. , Gunson M. R. , Aellig C. , Kämpfer N. , Abbas M. M. , Abrams M. C. , Brown T. L. , Chang A. Y. , Goldman A. , Irion F. W. , Newchurch M. J. , Rinsland C. P. , Stiller G. P. , Zander R.
Published: February 2004

Measured stratospheric mixing ratios of HCl, ClNO3, and ClO from ATMOS and MAS are poorly reproduced by models using recommended kinetic parameters. This discrepancy is not resolved by new rates for the reactions Cl+CH4 and OH+HCl derived from weighted fits to laboratory measurements. A deficit in modeled [HCl] and corresponding overprediction of [ClNO3] and [ClO], which increases with altitude, suggests that production of HCl between 20 and 50 km is much faster than predicted from recommended rates.
Lower hybrid turbulence and ponderomotive force effects in space plasmas subjected to large‐amplitude low‐frequency waves
Authors: Khazanov G. V. , Moore T. E. , Krivorutsky E. N. , Horwitz J. L. , Liemohn M. W.
Published: February 2004

It is demonstrated that large‐amplitude low‐frequency waves (LFW) can generate lower hybrid waves (LHW) in the auroral zone and ring current region. The LHW could then heat the ions. The ion energization due to the LHW may be comparable with that produced by the ponderomotive force of the LFW.
Dynamos driven by poloidal flow exist
Authors: Love J. J. , Gubbins David
Published: February 2004

We have discovered a class of dynamos driven by purely poloidal fluid motion, thereby demonstrating that toroidal motion is not essential for dynamo action and that there is no counterpart to the antidynamo theorem that purely toroidal motions cannot generate magnetic fields. The fully three‐dimensional (3D) dynamo action of these models results from the pushing and twisting of magnetic field lines by helical motion in a manner akin to the α² mechanism of mean‐field electrodynamics. No dynamo with dipole symmetry was found for an axisymmetric distribution of helicity; indeed, some azimuthal variation in helicity is required. Among the suite of dynamos that we have investigated, the poloidal flow dynamo with the smallest critical magnetic Reynolds number is very nearly the dynamo with the most nonaxisymmetric distribution of helicity.
Influence of embedded fractures on contaminant diffusion in geological formations
Authors: Berkowitz Brian , Scher Harvey
Published: February 2004

Crystalline rock formations are prime candidates for siting of repositories for radioactive and toxic wastes. Even the possibility of tenuous proximity of these sites to the biosphere requires realistic means of predicting subtle features of contaminant migration, such as very low‐level seepage. We generate percolation clusters to reproduce the often observed ramified embedded fracture structures in these formations. Diffusion paths through these clusters and the shortest spans of rock between them can so significantly decrease contaminant breakthrough times that previous estimates can be in error by up to an order of magnitude. Our analysis suggests that current methods for determining the suitability of geological formations as natural barriers to contamination are inadequate, and may result in dangerously misleading conclusions.
Determination of frequency dependent Love and Shida numbers from VLBI data
Authors: Haas Rüdiger , Schuh Harald
Published: February 2004

The solid Earth tide model as recommended by the IERS standards [McCarthy, 1992] and used in standard Very Long Baseline Interferometry [VLBI] data analysis only approximates to the first order the frequency dependence of the tidal deformation due to the Free Core Nutation [FCN] resonance. It is shown that frequency dependent second degree Love and Shida numbers have to be taken into account if the tidal displacements are to be modeled to better than ±5 mm. We also determined second degree Love and Shida numbers for different tidal bands (long‐period, diurnal, semidiurnal) and third degree Love and Shida numbers from VLBI data. The results for the different parts of the tidal spectrum are slightly different and a clear resonance can be seen around the FCN. The FCN period was determined to 426±20 sidereal days in the celestial reference frame.
Reply to “Probability of chance correlations of earthquakes with predictions in areas of heterogeneous seismicity rate: The VAN Case,” by M. Wyss and A. Allmann
Authors: Varotsos P. , Eftaxias K. , Lazaridou M. , Dologlou E. , Hadjicontis V.
Published: February 2004

All conclusions of Wyss and Allmann [1996] (hereafter cited as WA) are wrong, because their methodology is false. For example, WA's main conclusion reads: “the probability [P] that the observed correlations of [VAN] predictions with earthquakes (…11 out of 23 attempts) was due to chance is estimated as…96%…” However, when following WA's procedure exactly, and assuming that all 23 predictions (out of 23 attempts) are correct, we find a paradox, i.e., values of the probability P larger than unity. In view of this example, any further discussion on WA's claims becomes unnecessary. However, we proceed to detailed replies, point by point, in order to show that WA have also made several mistakes and major misinterpretations of the true content of VAN's statements.

Characteristic examples of the various misinterpretations (and mistakes) made by WA include: (i) a direct comparison of predicted magnitude values with Ms(PDE), while VAN had clearly stated that the magnitude values mentioned in the predictions correspond to Ms(ATH), i.e., to ML+0.5. Such a comparison is not allowed because ML+0.5 significantly differs (i.e., on the average by 1.0 unit) from Ms(PDE), (ii) an addition (or deletion) of critical wording to the VAN statements (and predictions) so that they distort VAN's true meaning, (iii) the use of 22 day prediction time window in the large majority of predictions which, however, correspond to single SES (and hence to an 11 days prediction time window), (iv) an incorrect statement that Varotsos et al. [1993a,b] define the acceptable uncertainty as ΔM ≤ 1.0, while VAN repeatedly published that a prediction is accepted as successful only when ΔM ≤ 0.7, (v) an erroneous claim that when using SI‐NOA “12 out of 22 VAN predictions fail to conform to the error limits,” while the reader can easily check that only 6 (or 7) out of 23 cases deviate from the error limits. Furthermore, WA grossly overestimated the number of the earthquakes (EQs) that should have been predicted, i.e., while VAN clearly stated that predictions are issued only when the expected magnitude is larger than (or equal to) 5.0 units, WA erroneously demand that VAN should predict all EQs with Ms ≥ 4.3 or Ms ≥ 4.0. Hence they characterize as a “missed earthquake” any event with Ms≥ 4.3 (or Ms ≥ 4.0 respectively) for which prediction was not issued.

Last but not least, we recall that Wyss and Baer [1981] published long term predictions in Greece (for the same time period discussed in this debate) ‐referring to expected EQs with magnitude 7.75‐ which turned out to be completely unsuccessful.
Reply to “A false alarm based on electrical activity recorded at a VAN‐Station in northern Greece in December 1990,” by J. Drakopoulos and G. Stavrakakis
Authors: Varotsos P. , Eftaxias K. , Lazaridou M.
Published: February 2004

Drakopoulos and Stavrakakis [1996] ‐hereafter called DS‐ select in their discussion one public alarm (issued on January 1991), but delete three other such cases (issued on Sept. 1988, April 1990 and Febr.–March 1993) which were followed by destructive seismic activities. (In other words, only one public alarm was issued during the period 1987–1989 discussed in the present Debate, but this is not discussed by DS.) For the three latter alarms Drakopoulos and/or co‐workers disagreed with the VAN predictions and, two to ten days before the corresponding earthquakes (EQs), publicly claimed that “no significant activity is expected.”. In the case selected here by DS, they report the seismic data within 22 days after the alarm but they do not mention that the EQ activity started on the morning of the 23rd day and lasted the next five days. Furthermore, DS misinterpreted our prediction which was submitted to Tectonophysics [see Varotsos et al., 1991] before the EQ occurrence.
Reply II to “VAN: Candidacy and validation with the latest laws of the game,” by F. Mulargia and P. Gasperini and “Precursor candidacy and validation: The VAN Case so far,” by F. Mulargia and P. Gasperini
Authors: Varotsos P. , Eftaxias K. , Lazaridou M.
Published: February 2004

A simple inspection of the Tables of Mulargia and Gasperini [1992, 1996a] that refer to the period 1987–1989 reveals the following two facts: (i) by recalling that predictions are issued only when the expected magnitude is Mpred ≥ 5.0, the true VAN success rate is 79% (for Δr ≤ 120km) while the (incorrect) success rate of 45% emerges when restricting only correlations that include earthquakes with MEQ≥5.0 are considered as successes, and (ii) the VAN alarm rate increases significantly for larger earthquake magnitudes, i.e., for MEQ≥5.0, 5.3, 5.5 and 5.8, the alarm rates are 22%, 36%, 50% and 60% respectively. These facts are inconsistent with their claim that “VAN results can be ascribed to chance.” This claim also contradicts the conclusions obtained from the calculations by Aceves et al. [1996], and by Honkura and Tanaka [1996].

In a separate Section we give answers, point by point, to various statements made in the two papers by Mulargia and Gasperini [1996a,b]. Most of these statements are obviously untrue. For example, they claim that “VAN predictions have been documented primarily by circulating telegrams among the members of the VAN‐group” although: (i) the Greek Authorities (as well as 29 International Institutes) receive the VAN predictions well before the earthquake occurrence and (ii) it is extensively known that the two most destructive activities in Greece during the period 1987–1994 were publicly announced by VAN well in advance. Furthermore, Mulargia and Gasperini [1996a] claim that, for the period 1990–1992, VAN correctly predicted only 2 out of 16 EQs with Ms(=mb+0.3) ≥ 5.0; however, a check of the VAN data of this period (see Varotsos et al., 1993c) shows that the alarm rate is 8/20, for EQs with mb > 4.7, and increases to 3/4 for EQs with mb > 5.0.
Reply to “Probability of earthquake occurrence in Greece with special reference to the VAN predictions,” by Y. Honkura and N. Tanaka
Authors: Varotsos P. , Lazaridou M.
Published: February 2004

The calculation of Honkura and Tanaka [1996] and that of Aceves et al. [1996], provide important tools for the clarification of the main question of this issue, i.e., whether or not the VAN predictions can be ascribed to chance.

Honkura and Tanaka's [1996] calculation showed that, in a circular area with a radius of 120 km and for the time window of 22 days, the probability P of occurrence of an earthquake (EQ) with Ms ≥ 5.0 in Greece is less than 0.25, and even smaller for a time window of 11 days. For larger magnitude thresholds, i.e., Ms ≥ 5.5 or Ms ≥ 5.8 (and in view of Gutenberg‐Richter relation), their P‐value has to be drastically smaller. A simple comparison of these P‐values with the Tables of Mulargia and Gasperini [1992, 1996a] immediately reveals that VAN‐predictions cannot be ascribed to chance. Note that an inspection of the latter Tables leads to (i) the VAN success rate is 40∼45% (when considering correlations with earthquakes having MEQ ≥ 5.0 only), and (ii) the VAN alarm rates increase with the (earthquake) magnitude threshold, reaching to values of 50% and 60%, for MEQ ≥ 5.5 and MEQ ≥ 5.8 respectively.

Another important point, which emerges from the calculation of Honkura and Tanaka [1996], is that “aftershocks must be treated carefully.” This strengthenes our remarks in Principles 4 and 5 of Varotsos et al. [1996a] that the inappropriate treatment of aftershocks in Mulargia and Gasperini’ [1992] calculation (which was based on Poisson distribution): (i) changed drastically the values of the significance level and (ii) turned a true “forward time correlation,” between predictions and earthquakes, to a “backward time association.” The latter point is also separately checked by Honkura and Tanaka [1996] who conclude that:“…with the backwards time correlation in mind… we could not find cases in which a high probability arises for the occurrence of an EQ of Ms ≥ 5.0 in the target area.” In this Reply we also proceed to some necessary clarifications, concerning the calculation of the “success rate” and “alarm rate” when a prediction method has, as expected, an experimental error in the magnitude determination.
Reply to “Earthquake prediction evaluation standards applied to the VAN Method,” by D. D. Jackson
Authors: Varotsos P. , Lazaridou M. , Hadjicontis V.
Published: February 2004

Our earlier publications show that VAN method does not fail requirements (1) and (2) suggested by Jackson [1996]. No subjective ex‐post facto decission was necessary for the evaluation of the success because, for the large majority of VAN predictions, the values of ΔM, Δr and Δt were published before the period 1987–1989 under discussion; in a few cases only (three out of 29), related with the observation of the new phenomenon of the SES electrical activity, the value of Δt was determined in 1988. Furthermore, a careful inspection‐from physical point of view‐shows that the three plausibility criteria, suggested by Jackson (to be obeyed by a candidate prediction technique), are actually met by VAN‐method.
New inferences of mantle viscosity from joint inversion of long‐wavelength mantle convection and post‐glacial rebound data
Authors: Forte Alessandro M. , Mitrovica Jerry X.
Published: February 2004

We perform joint inversions for mantle viscosity of geophysical observables associated with both mantle convection and glacial isostatic adjustment (GIA). Our data include coefficients of the non‐hydrostatic geoid (up to degree 8) and decay times associated with post‐glacial relative sea level (RSL) variations in Hudson Bay and Fennoscandia. We find that both data sets may be reconciled using a single profile of mantle viscosity which is characterized by a significant increase, with depth, across this region. This result weakens previous arguments that the mantle rheology has significant transient effects. The viscosity profiles we obtain are found to reconcile the observed free air gravity anomaly over Hudson Bay.
Finite fault source study of the Great 1994 Deep Bolivia Earthquake
Authors: Antolik M. , Dreger D. , Romanowicz B.
Published: February 2004

We apply an empirical Green's function method to recordings of teleseismic body waves from the June 9, 1994 deep‐focus Bolivia earthquake. The far‐field source time functions reveal that rupture occurred on a sub‐horizontal fault plane. The main rupture began some 25 km to the east of the hypocenter, consists of three large subevents, and covers a total area of about 60×40 km². The static stress drop is quite large, more than 150 MPa, and the obtained rupture velocity is less than 2 km/sec. While the total dimensions of the earthquake are large compared to estimates of the width of a metastable olivine wedge at this depth, the moment release is confined largely to a narrow band along an EW axis, and may be compatible with phase transitions within a thickened slab core.
A seismic image of the upper mantle beneath the North American Craton
Authors: Bostock M. G.
Published: February 2004

Teleseismic P‐waves recorded on the Canadian National Seismograph Network are used to investigate upper mantle structure beneath the North American craton. 1090 broadband seismograms are source‐normalized and stacked in 100 bins between 30° and 100° epicentral distance. The resulting image reveals a number of P to S converted phases which include prominent Ps conversions from the 410‐ and 660‐km discontinuities. Reduction of these signals to single traces via simultaneous deconvolution along theoretical moveout curves permits the analysis of and over a range of frequencies. Relative amplitudes vary with dominating at higher frequencies. This results in a greater pulse width for in broadband stacks and supports previous suggestions that the phase transformation responsible for the 410‐km discontinuity occurs over a narrower transition than that at 660 km. The image and single trace stacks are examined for evidence of discontinuities at other levels, notably at 520 km and 220 km depth. No obvious expression of is evident at high frequencies, and evaluation of lower frequency stacks is complicated by sidelobe interference from and . Evidence in support of a weak 220‐km interface is present in the form of an amplitude maximum at the expected time and slowness of a phase.
Fluids below the hypocentral region of Latur Earthquake, India: Geophysical indicators
Authors: Gupta Harsh K. , Sarma S. V. S. , Harinarayana T. , Virupakshi G.
Published: February 2004

A set of geophysical measurements and observations was undertaken to investigate the nature of the crust beneath the epicentral region of the deadly Mw 6.1 Latur earthquake of September 30, 1993. With an estimated focal depth of 2.6 km and the associated well defined but subtle surface ruptures, it is a rare stable continental region (SCR) earthquake with surface rupture. The focal depth of 69 out of 73 well located aftershocks is less than 5.5 km. Broad band (10³–10−3Hz) magnetotelluric (MT) soundings reveal the presence of an anomalously high conductivity zone at a shallow depth range of 6–10 km. Consistent with this result is the observation of a Pc phase, lagging behind the Pg phase by about 0.6 to 0.8 sec in the aftershock seismograms indicating a low velocity layer (LVL) at 7 to 10 km depth. A Bouguer gravity low of 5 m.gal, nearly coincident with this feature, is also observed. Above evidences indicate that the focal zone of the Latur earthquake sequence is limited to depths of about 5 to 6 km in the upper crust by an underlying low‐velocity and high conductivity layer. We interpret this high conductive, low velocity layer as a fluid filled fractured rock matrix. The inferred stress regime, including due to uplift of the Deccan Plateau, triggered by erosion of basalt cover is likely to be confined mostly in the upper part of the crust. Existence of a low velocity, high conductivity fluid filled layer will enhance stress concentration in the uppermost brittle part of the crust causing mechanical failure.
Petrology of basaltic glasses from the TAG Segment: Implications for a deep hydrothermal heat source
Authors: Meyer Peter S. , Bryan Wilfred B.
Published: February 2004

The trace element composition of basaltic glasses from the TAG segment of the MAR indicate that magmas erupted on the surface are derived from multiple primary magmas with Ce/Sm ratios varying from 2.2 to 3.9. In the pseudoquaternary system olivine‐plagioclase‐clinopyroxene‐quartz, TAG glasses cluster between the 4 and 6 kb phase boundaries. This suggests that TAG primary magmas evolve by crystallization at moderate to high pressure, then ascend rapidly to the surface with very short residence times and limited degrees of crystallization in shallow chambers. Such a plumbing system implies a deep‐seated heat source for hydrothermal circulation.
DE particle and field observations during the poleward expansion of an auroral surge through the plasma sheet
Authors: Anderson P. C. , Lyons L. R.
Published: February 2004

A substorm surge on September 25, 1981 was observed by the imagers on the high‐altitude DE‐1 spacecraft and encountered by the coplanar, low‐altitude DE‐2 spacecraft. This case is unique among those that we examined in that DE‐2 traversed the surge during the ∼10–15 min period of its rapid poleward motion through the plasma sheet. Because of this, the DE‐2 measurements provide a critical test for the recent proposal that the substorm expansion phase is due to an anti‐sunward‐propagating reduction in the large‐scale magnetospheric electric field imparted to the magnetosphere from the solar wind [Lyons, 1995]. A specific prediction of this theory is that the electric field reduction in the equatorial magnetosphere maps to the ionosphere as a poleward‐moving electric field reduction. In the ionosphere, large growth‐phase electric fields are expected poleward of the active surge aurora, and significantly weaker electric fields are expected equatorward of the active aurora. This electric field pattern is expected to propagate poleward through the plasma sheet with the surge. The DE‐2 measurements show significant southwestward electric fields within the portion of the plasma sheet poleward of the active auroral region, and greatly reduced electric fields within, the heated central plasma sheet that was left behind by the narrow region of poleward‐moving, active aurora. We also find weak electric fields equatorward of the region of active aurora in typical DE‐2 passes over auroral surges, where the region of active aurora had moved poleward to very near the magnetic separatrix prior to the satellite pass. These observations agree strongly with the Lyons [1995] predictions. Consistent with previous observations, the DE‐2 measurements also show strong and variable electric fields within the region of active surge; however these fields are not specifically addressed by the theory.
Correction to “Initial results from the ICEMELT Experiment: Body‐wave delay times and shear‐wave splitting across Iceland”
Authors: Bjarnason Ingi Th. , Wolfe Cecily J. , Solomon Sean C. , Gudmundson Gunnar
Published: February 2004

We present results from the first stage of the ICEMELT broadband seismometer experiment designed to determine upper mantle structure beneath Iceland, a hotspot located on the Mid‐Atlantic Ridge. Relative delays of teleseismic body waves across Iceland are in excess of 1 s for P waves and as large as 3 s for S waves. The patterns of P and S wave delays suggest a low‐velocity anomaly in the upper few hundred kilometers (100‐350 km) beneath central Iceland, consistent with the signature of mantle upwelling beneath a hotspot. Shear‐wave splitting measurements of the fast polarization direction ϕ and the delay time δt between the fast and slow shear waves have been obtained at several network stations. Splitting times range from 0.7 to 1.7 s, and fast directions are generally between N20°W and N45°W. While splitting times of this magnitude must be primarily signatures of the anisotropy of the Icelandic upper mantle, the directions of fast polarization are inconsistent with simple models of horizontally diverging flow either in the plate spreading direction or radially from the center of the hotspot. A hypothesis consistent with splitting data obtained to date is that the dominant contribution to upper mantle anisotropy is from the large‐scale mantle flow field of the North Atlantic.
Numerical simulation of the dynamical response of the Arctic Vortex to Aerosol‐associated chemical perturbations in the lower stratosphere
Authors: Zhao Xuepeng , Turco Richard P. , Jim Kao C.‐Y. , Elliott Scott
Published: February 2004

A general circulation model has been coupled interactively to a stratospheric photochemistry model to study the dynamical response of the Arctic polar vortex to ozone depletion catalyzed by volcanic aerosols. It is found that temperatures may be depressed by as much as 3–7 K in late March in the lower stratosphere at northern mid‐ and high‐latitudes owing to ozone‐radiation‐dynamics feedback effects. A corresponding delay in the breakdown of the stratospheric vortex (that is, the final warming) is predicted. Further, a dipole‐like anomaly in the zonal‐mean zonal wind, extending downward from the stratosphere into the troposphere, is found. In the model, the reduced solar heating in late winter and early spring associated with aerosol ozone depletion acts as a trigger for the net cooling that is observed. However, a major part of the cooling is related to anomalies induced in the circulation of the lower stratosphere. Our simulations demonstrate the close coupling between the dynamics and chemistry of the lower stratosphere, and the complexity in analyzing cause and effect related to perturbations in this region.
MAS measurements of the latitudinal distribution of water vapor and ozone in the mesosphere and lower thermosphere
Authors: Bevilacqua R. M. , Kriebel D. L , Pauls T. A. , Aellig C. P. , Siskind D. E. , Daehler M. , Olivero J. J. , Puliafito S. E. , Hartmann G. K. , Kämpfer N. , Berg A. , Croskey C. L.
Published: February 2004

We present measurements of the latitudinal variation of nighttime O3 and H2O in the mesosphere and (for O3) lower thermosphere obtained with the Millimeter‐wave Atmospheric Sounder (MAS) instrument during the ATLAS 2 mission (8–15 April 1993). These are the first such measurements that have ever been reported. They indicate an O3 mixing ratio minimum at mid‐latitudes in the upper mesosphere, with maxima in the tropics and at high latitudes. The H2O retrievals indicate H2O mixing ratios decreasing toward the poles in both hemispheres in the upper mesosphere. We also present measurements of the diurnal variation of O3 at southern mid‐latitudes, at higher vertical resolution than has ever been reported previously. The results are generally consistent with previous measurements and modeling studies.
Scale analysis to sort the different causes of mean sea level changes: An application to the northern Adriatic Sea
Authors: Marzocchi Warner , Mulargia Francesco
Published: February 2004

The variations in the relative sea level occur at very different scales both in space and time and reflect the combined variations of the absolute sea and land levels. An effective separation between these and the identification of the single physical processes responsible for the sea level changes observed in a given region and period of time can be achieved through a scale analysis. While the spatial extent of the phenomenon is characterized by comparing statistically the data at local, regional and global scales, the time extent is characterized by studying the different regimes in the series through a nonparametric change‐point algorithm. The details of the procedure are presented by an application to the variation of mean sea level in the northern Adriatic sea in the last century. The mean sea level in the region is found to be inhomogeneous both in time and space. The rate of increase in mean sea level is at some sites equal to that of the Mediterranean basin, which in turns equals the change in global mean sea level. At other sites, starting from about year 1950, the rate is one order of magnitude larger. The latter suggests soil compaction due to water draining from the water bearing table for agricultural use as the main active factor.
Mars as the parent body of the CI carbonaceous chondrites
Authors: Brandenburg John E.
Published: February 2004

The hypothesis that the CI meteorites have an origin on southern Mars is presented. This hypothesis is based on the CI containing a Martian pattern of oxygen isotopes and mineralogy indicative of deposition by liquid water, as found in several Martian meteorites. Other correlation's are discussed. A model of the formation of CI meteorites as being late planetary accretion material that was concentrated as bottom sediment of lakes or seas in early Mars history is proposed. The model accounts for the similarity to solar composition of the CIs because during the late accretion on Mars the upper regolith would receive material that was Martian in isotopic abundance but primordial in composition.
Trends of OCS, HCN, SF6, CHClF2 (HCFC‐22) in the lower stratosphere from 1985 and 1994 Atmospheric Trace Molecule Spectroscopy Experiment measurements near 30°N latitude
Authors: Rinsland C. P. , Mahieu E. , Zander R. , Gunson M. R. , Salawitch R. J. , Chang A. Y. , Goldman A. , Abrams M. C. , Abbas M. M. , Newchurch M. J. , Irion F. W.
Published: February 2004

Volume mixing ratio (VMR) profiles of OCS, HCN, SF6, and CHClF2 (HCFC‐22) have been measured near 30°N latitude by the Atmospheric Trace Molecule Spectroscopy Fourier transform spectrometer during shuttle flights on 29 April–6 May 1985 and 3–2 November 1994. The change in the concentration of each molecule in the lower stratosphere has been derived for this 9 1/2‐year period by comparing measurements between potential temperatures of 395 to 800 K (∼17 to 30 km altitude) relative to simultaneously measured values of the long‐lived tracer N2O. Exponential rates of increase inferred for 1985–to–1994 from these comparisons are (0.1 ± 0.4)% yr−1 for OCS, (1.0±1.0)% yr−1 for HCN, (8.0±0.7)% yr−1 for SF6, and (8.0±1.0)% yr−1 for CHClF2 (HCFC‐22), 1 sigma. The lack of an appreciable trend for OCS suggests the background (i.e., nonvolcanic) source of stratospheric aerosol was the same during the two periods. These results are compared with trends reported in the literature.
Modeling of F‐region ionospheric upflows observed by EISCAT
Authors: Caton R. , Horwitz J. L. , Richards P. G. , Liu C.
Published: February 2004

High‐latitude ionospheric bulk parameter profiles measured with the European Incoherent Scatter Radar (EISCAT) system are modeled with a modified version of the Field Line Interhemispheric Plasma (FLIP) code. Three observed profiles of field‐aligned ion velocities, densities, and ion and electron temperatures for the altitude range 200–800 km are modeled as influenced by the effects of soft (<1 keV) auroral electron precipitation, convection‐driven frictional ion heating, and downward magnetospheric electron heat fluxes. Favorable matches between the observed and modeled profiles with reasonable precipitation, convection, and downward electron heat flux parameters suggest that soft electron precipitation, together with magnetospheric electron heat fluxes, are the primary drivers of the normal ionospheric F‐region upflows observed at high latitudes.
GPS detection of ionospheric perturbations following a space shuttle ascent
Authors: Calais Eric , Bernard Minster J.
Published: February 2004

The exhaust plume of the Space Shuttle during its ascent is a very powerful source of energy that excites atmospheric acoustic perturbations. Because of the coupling between neutral particles and electrons at ionospheric altitudes, these low frequency acoustic perturbations induce variations of the ionospheric electron density. We computed ionospheric electron content time series using Global Positioning System data collected on Bermuda island during the STS‐58 Space Shuttle launch. The analysis of these time series shows a perturbation of the ionospheric electron content following the launch and lasting for 35 mn, with periods less than 10 mn. The perturbation is complex and shows two sub‐events separated by about 15 mn at 200 km from the source. The phase velocities and waveform characteristics of the two sub‐events lead us to interpret the first impulsive arrival as the direct propagation of the shock wave front, followed by oscillatory guided waves probably excited by the primary shock wave and propagating along horizontal atmospheric interfaces at 120 km altitude and below.