Convergent boundaries and related igneous and metamorphic complexes in caledonides of Central Asia

Fragments of the crystalline complexes where Vendian metamorphism of moderate and elevated pressure predated Early Paleozoic metamorphism have been established in the accretionary-collisional domain of the eastern segment of the Central Asian Foldbelt (Early Caledonian superterrane of Central Asia). The geodynamic setting of the Vendian (??560?C570 Ma) South Hangay metamorphic belt located in the junction zone of the Baydrag Block and the Late Riphean (??665 Ma) ophiolite complex of the Bayanhongor Zone is considered. The origination of this belt was related to the formation of the convergent boundary in the framework of the Zabhan microcontinent about 570 Ma ago. At the same time, an island-arc complex was formed in the paleo-oceanic domain. Metamorphism of elevated pressure indicates that Vendian structures with sufficiently thick continental crust were formed in the framework of the continental blocks. Vendian metamorphism is also established in the Tuva-Mongolia Massif and the Kan Block of the Eastern Sayan. These data show that the Late Baikalian stage predated the evolution of the Early Caledonian superterrane of Central Asia. The development of its accretionary-collisional structure was accompanied by Late Cambrian-Early Ordovician low-pressure regional metamorphism. Granulite-facies conditions were reached only at the deep levels of the accretionary-collisional edifice. The outcrops of crystalline complexes in the southern framework of the Caledonian paleocontinent are regarded as fragments of the Early Paleozoic Central Mongolian metamorphic belt.     

Advances in noctilucent cloud research in the space era

A summary of NLC research in the last two decades is presented. Results of NLC studies from the near-Earth space are discussed. It is shown that NLC can cover much larger territories than those estimated earlier and that there exists asymmetry in the coverage and also in the physical properties of NLC in the Northern and Southern Hemispheres. The mesopause often reveals a compelx multilayered structure. The pilot program of NLC research is discussed as a subprogram of the Middle Atmosphere Program and some vistas in NLC research are discussed.     

Investigating the Summertime Low-Level Jet Over the East Coast of the U.S.A.: A Case Study

The vertical structure of the marine atmospheric boundary layer (MABL) and the summertime low-level jet (LLJ) along the east coast of the U.S.A. was studied in the framework of a joint expedition (CBLAST-Low), carried out during the summer of 2003 (31 July–27 August) at Nantucket island, Massachusetts, U.S.A. Analyzing measurements from radiosondes, in-situ and remote sensing systems, it was found that within the lower part of the stable MABL, intermittent and persistent LLJ events were frequently observed. Evidence is presented implying that the analyzed jet case was induced by the interaction of a slow-moving cyclone over north-eastern U.S.A. and the stationary high pressure system over the Atlantic Ocean, as well as by the sloping inversion of the MABL. Focused on a 5-day period of persistent south-westerly (marine) flow, the analysis of sodar and radiosonde data revealed the presence of a stable layer associated with increased static stability just before the emergence of low-level flow acceleration. As indicated by the Richardson number profiles, the increased stability of the lower MABL suppressed turbulence, allowed the decoupling of LLJ from friction, providing a favourable environment for the development of inertial oscillations. Significant amplitudes of inertial motions, which were confirmed by the application of a Hilbert–Huang transform, are associated with the acceleration at the LLJ’s core, due to the frontal events and the subsequent frictional decoupling, both leading to a modification of the large-scale flow structure.     

Terrain analysis for active tectonic zone characterization: a new application for MODIS night LST (MYD11C3) data set

A new context for active tectonic zone recognition is proposed on the basis of the exporting energy of the terrain features at continental scale. Toward this end, elevation, latitude, and longitude decorrelation stretch of multi-temporal moderate resolution imaging spectroradiometer (MODIS) monthly average land surface temperature (LST) imagery (MYD11C3) is applied in a study area extending from Red Sea to Indian Ocean and from Persian Gulf to Black Sea and Caspian Sea. Multiple linear regression analysis of principal components images (principal components analysis (PCAs)) quantified the variance explained by elevation, latitude, and longitude. Selective variance reduction reconstructed the multi-temporal LST imagery from the residual images and selected PCAs by taking into account the portion of variance that is not related to elevation, latitude, and longitude. The reconstructed imagery presents the magnitude the standardized LST value per pixel deviates from the elevation, latitude, and longitude predicted one, whereas a positive LST anomaly is defined as a region that presents positive reconstructed LST value throughout the year. Clustering of the reconstructed standardized imagery mapped a great positive LST anomaly of tectonic origin that occupies the greatest in elevation and most massive areas, forming three regions: (a) the Himalayan Belt along the Pakistan, Afghanistan borders, and the Eastern Alpine zone (Makhran Ranges and Zagros Ranges), (b) the coastal zone (along the Red Sea) of the Arabian Shield, and (c) the Oman Mountains Province along the Persian Gulf. The method will allow the classification of terrain objects (e.g. mountains, basins) on the basis of both the exporting energy (reconstructed LST) and geomorphometry.     

A Probabilistic Estimation of Strong Earthquakes'''' Occurrence in Aeghion Area, Central Greece

INTRODUCTIONTheexaminedareaislocatedintheGulfofCorinthandhasbeenrecognizedasoneofthemostactiveriftsinthewholeAegeanSea .Itsquaternarynormalfaulting (Sebriere ,1 977)anditshighseismicity (PapazachosandPapazachou ,1 997;AmbraseysandJackson ,1 990 )makeitaphysicallaboratorywithintheMediterraneanarea ,wherethephysicalprocessrelatedtotheseismiccyclecouldbestudied .ThecityofAeghionexperiencedastrong (MW =6 4 )earthquakeinJune 1 995,whichcausedseveredamage (Tselentis ,etal.,1 996 ) .Twent…     

Numerical experiments in the 3/1 andv 6 overlapping resonance region

Numerical experiments of fictitious small bodies with initial eccentricities e=0.1 have been performed in the overlapping region of the 3/1 mean motion resonance and of thev ₆ secular resonance 2.48a2.52AU for different values of the initial inclination 16°i20°. An analysis for thev ₆ secular resonance shows that the topology is different from the one found outside the overlapping region: the critical argument for thev ₆ resonance in the overlapping region rotates in opposite direction as compared to the purev ₆ region. In the 3/1 resonance region the secular resonancev ₅ is dominant, and some secondary secular resonances asv ₆ –v ₁₆ andv ₅ +v ₆ are present.     

Über einen eruptiven Veränderlichen in Hercules

On plates of the 60/90 cm Schmidt-telescope of the Jena University Observatory taken 1967 June 29 up to August 2 an eruptive variable with a maximum magnitude B = 15^m5 and an amplitude of at least 6 mag was found. There are indications that the object is a U Geminorum star of the subtype SW Ursae maioris.     

Potential of Earthquake Early Warning Systems

Despite their short warning times (seconds to tens of seconds)earthquake early warning systems can become useful tools in riskmitigation provided their design is robust and utilizes theregional tectonics. Bucharest can serve as a good example forsuch a system with a warning time of 25 seconds. Integration ofearly warning into real-time information systems turns out beingcrucial in disaster management.