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[1] We used a small array of portable seismographs to determine aftershock locations of the 2001 Gujarat earthquake. Our aftershock locations show a trend that dips toward the south at about 50°which is interpreted as the fault plane of the mainshock. The depth range of the aftershocks is from 10 to 35 km, which is somewhat deeper than other crustal earthquakes, and indicates that the faulting did not reach the surface. The area of the fault is about 40 Â 40 km 2 , which is small for a Mw7.7 earthquake and results in a high static stress drop of 13 to 25 MPa. There are no mapped faults or obvious topographic features along the surface projection of this fault. These findings show that very large damaging earthquakes can occur without producing surface faulting, which is an important issue for earthquake hazard assessments in continental regions.

The adsorption equilibria of seven trivalent metal ions (M(3+):  Sc(3+), Y(3+), La(3+), Fe(3+), Al(3+), Ga(3+), and In(3+)) on chelating resins containing iminodiacetic acid groups (-LH(2)) were studied. Adsorption curves, measured under the conditions of metal ions in excess against chelating groups, directly indicated the metal-to-ligand ratio of the complexes formed in the resin phase. Iron and group 13 metal ions were adsorbed as (-L)(2)HM, while group 3 metal ions were adsorbed as (-L)(3)H(3)M and (-L)(2)HM. The adsorption constants for (-L)(2)HM found for all the metal ions were well correlated with the formation constants of iminodiacetate complexes in aqueous solutions. The actual adsorption of group 3 metal ions was significantly enhanced beyond that expected from this correlation because of the formation of (-L)(3)H(3)M. This is why the selectivity in the adsorption of trivalent metal ions differs from that in the complexation of iminodiacetate in aqueous solutions. The effects of anions and the number of iminodiacetic acid groups per unit weight of resins were also discussed.

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Daily and seasonal variations of the monthly median F2‐region critical frequency (ƒoF2) in the Antarctic are examined. The abnormally large increase in ƒoF2 is found to be most distinctive in winter in the areas around Ellsworth, South Pole, Byrd, Little America, Cape Hallett, and Terre Adelie. Statistically, the increase occurs between 0400 and 0900 universal time, although individual days may differ. Synoptic maps of ƒoF2 indicate that areas of abnormally large ƒoF2 extend from the sunlit hemisphere across to the night hemisphere. Equivalent current systems of the magnetic variation coincide qualitatively with the ƒoF2‐distribution patterns. An explanation for this anomaly is given which takes into account the horizontal drift motion of electrons in the F2 region that is caused by the interaction of the electric field deduced from the magnetic Sq and Sd variation with the magnetic field in the polar regions. Time variations of the ƒoF2 worldwide distribution and of the F2‐region behavior as recorded on ionograms seem to support the drift theory.

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A helium plasma is produced by electron-cyclotron resonance heating in a cusp-configuration magnetic field. Several neutral helium lines are found polarized in the direction perpendicular to the magnetic field; the maximum polarization degree exceeds 10%. The polarization degree and intensity of the emission lines yield, respectively, the alignment and population of the upper levels. The population-alignment collisional-radiative model is developed, and the experimental result is interpreted in terms of an anisotropic electron velocity distribution; it is of a Saturn-type with the central thermal component of 14 eV and the 'ring' component displaced by 9.2 eV from the central component. The relative number of 'ring' electrons is 40%.

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