Mathematical modeling of nighttime enhanced electron density regions in the Earth’s ionospheric <Emphasis Type="Italic">F</Emphasis>2 layer and plasmasphere

A mathematical modeling method and the global numerical model of the Earth’s upper atmosphere were used to study nighttime enhanced electron density regions (EEDRs) in the ionospheric F2 layer and their possible manifestations at altitudes of the Earth’s plasmasphere. It has been established that EEDRs are formed owing to latitudinally nonuniform longitudinal (along the magnetic field) plasma flows from the plasmasphere into the nighttime ionosphere and the wind transport of ions along geomagnetic field lines. The specific features of the effect of ionospheric-plasmaspheric plasma transport processes, related to their three-dimensional character, on EEDRs have been revealed.     

On the geology of the Indoburman ranges

The mountains of western and northwestern Burma consist chiefly of colossal accumulations of Palaeocene to Eocene (Arakan and Chin Hills) or Senonian to Eocene (Naga Hills) Flysch of varying, including “exotic”, facies.

The main frontal thrust zone of the Alpino‐Himalayan Tectogene lies along and within the easternmost ranges of this Indoburman system, not along the western margin (Shan Scarp) of the Sinoburman Highlands. Some of the highest mountains in the Naga Hills are “Klippen” of metamorphics lying on Flysch.

The Flysch ranges arose during the Oligocene but along the Arakan Coast there is ample evidence of an equally important earlier orogenic phase (latest Cretaceous) now almost totally buried beneath the western half of the Indoburman system and the post‐Oligocene “Argille Scagliose” and “Macigno” on‐lapping eastwards from the Bengal‐Assam embayment.

The lowlands of Central and Lower Burma do not represent a foreland feature, but an intramontane Molasse‐filled basin to which the sea retained access because of a general southerly plunge of the Alpine Tectogene. Geotec‐tonically, it is analogous to the Tibetan Plateau, not the Indo‐Gangetic lowlands.     

Experimental petrology of alkalic lavas: constraints on cotectics of multiple saturation in natural basic liquids

Experimental study of natural alkalic lava compositions at low pressures (pO₂QFM) reveals that crystallization of primitive lavas often occurs in the sequence olivine, plagioclase, clinopyroxene, nepheline without obvious reaction relation. Pseudoternary liquidus projections of multiply saturated liquids coexisting with plagioclase (±olivine±clinopyroxene±nepheline) have been prepared to facilitate graphical analysis of the evolution of lava compositions during hypabyssal cooling. Use of (TiAl₂)(MgSi₂)_–1 and Fe³⁺ (Al)_–1 exchange components is a key aspect of the projection procedure which is succesful in reducing a wide range of compositions to a systematic graphical representation. These projections, and the experiments on which they are based, show that low pressure fractionation plays a significant role in the petrogenesis of many alkalic lava suites from both continental and oceanic settings. However, the role of polybaric fractionation is more evident in the major element chemistry of these lava suites than in many tholeiitic suites of comparable extent. For example, the lavas of Karisimbi, East Africa, show a range of compositions reflecting a polybaric petrogenesis from primitive picrites at 1360° C/18 kb and leading to advanced low pressure differentiates. Evolved leucite-bearing potassic members of this and other suites may be treated in a nepheline-diopside-kspar (+olivine+leucite) projection. Compositional curvature on the plagioclase+clinopyroxene+olivine+leucite cotectic offers a mechanism to explain resorption of plagioclase in alkalic groundmass assemblages and the incompatibility of albite and leucite. This projection is useful for evaluating the extent of assimilation of the alkalic portions of crustal granulites. Assimilation appears to have played some role in the advanced differentiates from Karisimbi.     

A fractal-multifractal approach to groundwater contamination. 2. Predicting conservative tracers at the Borden site

 In a companion paper (Puente et al., this issue), the capability of a deterministic fractal-multifractal (FM) approach to faithfully and compactly describe the geometry of chloride and bromide tracers gathered at the Borden site was illustrated. As trends in surrogate parameter space were found for successive plume contours (i.e. linear growth in coordinates by which fractal interpolating functions pass, nearly constant rotations and fairly high scalings), this article reports usage of a variety of prediction schemes, based on linear regressions and the aforementioned trends, in order to study the evolving plumes. It is shown that the FM representation leads to plausible non-Gaussian plume evolutions and yields predictions that closely approximate records for a period of time that extends even beyond one year. It is illustrated that such predicted geometries are also consistent with predictions made via stochastic theories (i.e. Dagan, 1984).     

Detection,Estimation of Magnitude,and Relative Location of Weak Aftershocks Using Waveform Cross-Correlation: The Earthquake of August 7, 2016, in the Town of Mariupol

The study of the stress-strain state of a medium in seismically quiet areas is difficult because of the absence of strong events. Under such circumstances, each earthquake, even relatively weak, is of high importance. In this case, all possible information on tectonic stresses and their dynamics, e.g., information on time, location, and magnitude of aftershocks, should be obtained from available seismic data. The earthquake near the town of Mariupol which occurred on August 7, 2016, had a body wave magnitude of 4.5–4.9 from the data of the different seismological centers. We detected 12 aftershocks that occurred within 5 days after the main shock using two seismic arrays (AKASG and BRTR) and one three-component station (KBZ) of the International Monitoring System, as well as two array stations of the Institute of Geosphere Dynamics, Russian Academy of Sciences. For six aftershocks, signals were found at three or more stations. The other aftershocks were detected from the data at two out of three nearest stations. Signal detection and association with aftershocks of the main shock, as well as estimation of magnitude and relative location of the found aftershocks, were carried out using the method of waveform cross-correlation (WFCC). The signals from the main shock that acted as the only master event (ME) for the WFCC method were used as waveform templates. To increase the signal-to-noise ratio and to determine the exact onset time of regular seismic waves from aftershocks, we used waveform templates of different length, from 10 to 180 s depending on the wave type and distance to the station, as well as band filtering in narrow frequency bands. The highest sensitivity of the detector and accuracy of the P-wave onset time estimates were reached when a waveform template included all regular waves from P to L _g . Association of signals with aftershocks was based on back projection of signal arrival times to origin times using the travel time from a master event to the station, which was measured with a very low error, being equal to almost half of the digitization step length. To develop a seismic event hypothesis, the origin times at two or more stations should be spaced within a 2-s interval.     

Determination of crustal movements in Turkey by terrestrial geodetic methods

In Turkey, neotectonic activity originated from the collision of the Arabian and Anatolian land masses during the Middle Miocene. As a result of the collision, westward escape of the Anatolian block introduced E-W compression in Western Turkey which began to be relieved by N-S extension. The North Anatolian Fault (NAF) is the major active strike-slip fault that was formed under the neotectonic regime. The rates of the motion along this fault estimated by several authors are in the range of 0.4–2.9 cm/a according to kinematic data. In Turkey, the first studies of crustal movements by geodetic methods were started in the west section of the NAF in 1972. So far, individual activities and studies coordinated by multidisciplinary projects have been realized in this region. The results obtained from available geodetic data indicate the motion of the Anatolian block relative to Eurasia.     

On the meridional circulation and balance of momentum in the Southern Ocean of POP

 The circulation of the Southern Ocean is studied in the eddy-resolving model POP (Parallel Ocean Program) by an analysis of zonally integrated balances. The TEM formalism (Transformed Eulerian Mean) is extended to include topography and continental boundaries, thus deviations from a zonally integrated state involve transient and standing eddies. The meridional circulation is presented in terms of the Eulerian, eddy-induced, and residual streamfunctions. It is shown that the splitting of the meridional circulation into Ekman and geostrophic transports and the component induced by subgrid and Reynolds stresses is identical to a particular form of the zonally integrated balance of zonal momentum. In this balance, the eddy-induced streamfunctions represent the interfacial form stresses by transient and standing eddies and the residual streamfunction represents the acceleration of the zonal current by density fluxes in a zonally integrated frame. The latter acceleration term is directly related to the surface flux of density and interior fluxes due to the resolved and unresolved eddies. The eddy-induced circulation is extremely vigorous in POP. In the upper ocean a shallow circulation, reversed in comparison to the Deacon cell and mainly due to standing eddies, appears to the north of Drake Passage latitudes, and in the Drake Passage belt of latitudes a deep-reaching cell is induced by transient eddies. In the resulting residual circulation the Deacon cell is largely cancelled and the residual advection of the zonal mean potential density is balanced by diapycnal eddy and subgrid fluxes which are strong in the upper few hundred meters but small in the ocean interior. The balance of zonal momentum is consistent with other eddy-resolving models; a new aspect is the clear identification of density effects in the zonally integrated balance. We show that the wind stress and the stress induced by the residual circulation drive the eastward current, whereas both eddy species result in a braking. Finally, we extend the Johnson–Bryden model of zonal transport to incorporate all relevant terms from the zonal momentum balance. It is shown that wind stress and induction by the residual circulation carry an eastward transport while bottom form stress and the stress induced by standing eddies yield westward components of transport. Received: 26 June 2001 / Accepted: 2 November 2001     

Experimental Petrology of Melilite Nephelinites

Experimental study of natural melilite nephelinite lavas ofintermediate K/Na ratio at low pressure (fo₂ reveals the presenceof a peritectic ‘point’ of distributary type (1090?C)for liquids saturated with leucite, nepheline, and spinel. Withdecreasing temperature on the olivine + melilite cotectic, botholivine and melilite react with such liquids to produce high-calciumpyroxene at the peritectic. Both the olivine + high-calciumpyroxene and melilite + high-calcium pyroxene cotectics arestable at temperatures below the peritectic. Olivines coexistingwith such liquids are much more magnesian than those in comparabletholeiitic liquids. The olivine-liquid Fe-Mg distribution coefficient is a monotonically increasing function of silica activity over the composition range spannedby melilite nephelinite, ugandite, alkali basalt, and tholeiitebasalt liquids. The analogous Fe-Mg distribution coefficientfor melilite and liquid is effectively constant , while that for high-calcium pyroxene and liquidis highly dependent on the chemistry of high-calcium pyroxene(cf., Sack & Carmichael, 1984). Pseudoternary liquidus projectionsof multiply saturated liquids coexisting with nepheline, leucite,and spinel (?olivine?high-calcium pyroxene?melilite) have beenprepared to facilitate graphical analysis of the evolution oflava compositions during hypabyssal cooling. Major element chemicalanalyses and petrographic features of lavas from Mt. Nyiragongo,East Africa and Oahu, Hawaii (e.g., Denaeyer et al., 1965; Wilkinson& Stolz, 1983) confirm the validity of these diagrams andthe systematics established from the experimental data. ^*Reprint requests to R.O. Sack