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Eastern Boundary (eastern + boundary)
Selected AbstractsAnalysis of the 2002 May earthquake sequence in the central Pyrenees, consequences for the evaluation of the seismic risk at Lourdes, FranceGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2004Noalwenn Dubos SUMMARY Three earthquakes of magnitudes 4.6, 4.3 and 3.7 occurred in 2002 May at two locations 20 km from the pilgrimage city of Lourdes in the French Pyrenees. They were well recorded by the permanent Pyrenean seismic networks, by a temporary local network, as well as by accelerometric stations. In order to understand their tectonic contexts, and to come to a better evaluation of the seismic risk at Lourdes, a detailed analysis of these events is performed. The first two events are located south of Lourdes in an area where only a few earthquakes have occurred up to now. Their focal solutions derived from first-motion polarities indicate reverse faulting, with a N110°E strike consistent with the geological structures. 10 aftershocks were recorded and relocated with respect to the main events, benefiting from the waveform similarity of the various events. This analysis reveals that the two main events concern probably the same fault, the second rupture being in the prolongation of the first one, whereas the other small aftershocks are located on fault segments in the vicinity of the hypocentre of the second event. The third large event, located to the SE of Lourdes, involves a normal mechanism with a N120°E plane parallel to the main geological structures. It occurred in a region of intense activity, including in particular an event of maximum macroseismic intensity IX in 1660. The first two events are at the boundary of a large quiet zone. In order to understand the related structural context, a new crustal tomographic model has been computed. It reveals that this quiet zone coincides with a block of high P -velocity. In contrast, the seismicity appears to be stronger at the northern and eastern boundaries of this block. The accelerometric data of the three main events recorded at Lourdes have been used to estimate the maximum peak ground accelerations in this city if a large event occurred, similar to those which damaged the city in the seventeenth and eighteenth centuries. Horizontal accelerations of 0.25 ± 0.07 g are predicted in the frequency domain 1,5 Hz at the location of the Sanctuary for a magnitude 6 event occurring 10 km away from the city. Taking into account the error bars, these values could in some cases exceed those specified by the building codes in this region. [source] Biodiversity and biogeography of the islands of the Kuril ArchipelagoJOURNAL OF BIOGEOGRAPHY, Issue 9 2003Theodore W. Pietsch Abstract Aim Based on seven consecutive seasons of biotic survey and inventory of the terrestrial and freshwater plants and animals of the 30 major islands of the Kuril Archipelago, a description of the biodiversity and an analysis of the biogeography of this previously little known part of the world are provided. Location The Kuril Archipelago, a natural laboratory for investigations into the origin, subsequent evolution, and long-term maintenance of insular populations, forms the eastern boundary of the Okhotsk Sea, extending 1200 km between Hokkaido, Japan, and the Kamchatka Peninsula of Russia. A chain of more than 56 islands, the system is only slightly smaller than the Hawaiian Islands, covering an area of 15,600 km2 and providing 2409 km of coastline. Methods Collections of whole specimens of plants and animals, as well as tissue samples for future molecular studies, were made by teams of scientists from Russia, Japan, and the USA, averaging 34 people for each of the seven annual summer expeditions (1994,2000). Floral and faunal similarities between islands were evaluated by using Sorensen's coefficient of similarity. The similarity matrix resulting from pair-wise calculations was then subjected to UPGMA cluster analysis. Results Despite the relatively small geographical area of all islands combined, the Kuril Island biota is characterized by unusually high taxonomic diversity, yet endemism is very low. An example of a non-relict biota, it originated from two primary sources: a southern source, the Asian mainland by way of Sakhalin and Hokkaido, and a northern source by way of Kamchatka. The contribution of the southern source biota to the species diversity of the Kurils was considerably greater than the northern one. Main conclusion The Bussol Strait, lying between Urup and Simushir in the central Kurils, is the most significant biogeographical boundary within the Archipelago. Of lesser importance are two transitional zones, the De Vries Strait or ,Miyabe Line', which passes between Iturup and Urup in the southern Kurils, and the fourth Kuril Strait, between Onekotan and Paramushir in the northern Kurils. [source] Metamorphism and microstructures along a high-temperature metamorphic field gradient: the north,eastern boundary of the Královský hvozd unit (Bohemian Massif, Czech Republic)JOURNAL OF METAMORPHIC GEOLOGY, Issue 4 2002D. Scheuvens Abstract A metamorphic field gradient has been investigated in the Moldanubian zone of the central European Variscides encompassing, from base to the top, a staurolite,kyanite zone, a muscovite,sillimanite zone, a K-feldspar,sillimanite zone, and a K-feldspar,cordierite zone, respectively. The observed reaction textures in the anatectic metapsammopelites of the higher grade zones are fully compatible with experimental data and petrogenetic grids that are based on fluid-absent melting reactions. From structural and microstructural observations it can be concluded that the boundary between the kyanite,staurolite zone and the muscovite- and K-feldspar,sillimanite zones coincides with an important switch in deformation mechanism(s). Besides minor syn-anatectic shearing (melt-enhanced deformation), microstructural criteria point (a) to a switch in deformation mechanism from rotation recrystallization (climb-accommodated dislocation creep) to prism Is Central Asia the eastern outpost of the Neandertal range?AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2009A reassessment of the Teshik-Tash child Abstract Since its discovery in southeastern Uzbekistan in 1938, the Teshik-Tash child has been considered a Neandertal. Its affinity is important to studies of Late Pleistocene hominin growth and development as well as interpretations of the Central Asian Middle Paleolithic and the geographic distribution of Neandertals. A close examination of the original Russian monograph reveals the incompleteness of key morphologies associated with the cranial base and face and problems with the reconstruction of the Teshik-Tash cranium, making its Neandertal attribution less certain than previously assumed. This study reassesses the Neandertal status of Teshik-Tash 1 by comparing it to a sample of Neandertal, Middle and Upper Paleolithic modern humans, and recent human sub-adults. Separate examinations of the cranium and mandible are conducted using multinomial logistic regression and discriminant function analysis to assess group membership. Results of the cranial analysis group Teshik-Tash with Upper Paleolithic modern humans when variables are not size-standardized, while results of the mandibular analysis place the specimen with recent modern humans for both raw and size-standardized data. Although these results are influenced by limitations related to the incomplete nature of the comparative sample, they suggest that the morphology of Teshik-Tash 1 as expressed in craniometrics is equivocal. Although, further quantitative studies as well as additional sub-adult fossil finds from this region are needed to ascertain the morphological pattern of this specimen specifically, and Central Asian Middle Paleolithic hominins in general, these results challenge current characterizations of this territory as the eastern boundary of the Neandertal range during the Late Pleistocene. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc. [source]
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