Building damage from the Marmara, Turkey earthquake of August 17, 1999

The objective of this paper is to provide a brief overview of damage as observed immediately following the earthquake. Detailed studies of structural seismic performance, conducted in the time elapsed since August 1999, are not the subject of this paper, but rather the object of other papers presented in this Special Issue of the Journal. Damage to reinforced concrete, masonry, and steel structures, is described. The mode the failure presented include: foundation failures; soft stories; strong beams and weak columns; lack of column confinement and poor detailing practice; buckling and fractures of steel members; and non-structural damage. Some general lessons learned from this earthquake are also formulated.     

A Tertiary asthenospheric flow beneath the southern French Massif Central indicated by upper mantle seismic anisotropy and related to the west Mediterranean extension

Upper mantle flow beneath the French Massif Central is investigated using teleseismic shear wave splitting induced by seismic anisotropy. About 25 three-component stations (short period, intermediate and broadband) were installed during the period 1998-1999 in the southern Massif Central, from the Clermont Ferrand volcanic area to the Mediterranean Sea. Teleseismic shear waves (SKS, SKKS and PKS) were used to determine the splitting parameters: the fast polarization direction and the delay time. Delay times ranging between 0.7 and 1.5 s have been observed at most of the sites. The azimuths of the fast split shear waves trend homogeneously NW-SE in the southern Massif Central suggesting a homogeneous mantle flow beneath this area. The observed NW-SE direction differs from the N100°E Pyrenean anisotropy further south. It does not appear to be correlated to Hercynian structures nor to the present-day motion of the plate but is well correlated to the Tertiary extension direction. We propose that the opening of the western Mediterranean induced by the rotation of the Corsica-Sardinia lithospheric block and the roll-back to the SE of the Tethys slab may have generated a large asthenospheric mantle flow beneath the southern Massif Central and a deflection of the up going plume centered beneath the northern Massif Central toward the SE.     

Radiogenic lead mobility in the Shea Creek unconformity-related uranium deposit (Saskatchewan,Canada): migration pathways and Pb loss quantification

The average Pb/U ratio of the Shea Creek unconformity-type uranium deposit has been estimated at 0.071±0.015. The calculation was performed on a volume enclosing the orebody to take into account the possible radiogenic lead migration within the ore zone. Despite this precaution, this ratio is significantly lower than the expected ratio (0.211) assuming a main U deposition around 1315 Ma, as suggested by previous UPb isotopic dating. Although part of the radiogenic lead can be trapped as galena within the orebody, about 60% of Pb have migrated more than 700 m away from the orebody, preferentially along the unconformity. To cite this article: P. Kister et al., C. R. Geoscience 336 (2004).     

Direct analysis of microaggregates shrinkage for drying: Application to microaggregates from a Brasilian clayey Ferralsol

Subrounded microaggregates 100 to 500 μm in diameter were collected in a Ferralsol located in the state of Goiàs. Observation of these microaggregates in dry conditions in scanning electron microscopy showed morphological characteristics that are representative of microaggregates described earlier in many Ferralsols. The shrinkage for drying of initially water saturated microaggregates was studied using an environmental scanning electron microscope. Results showed very small shrinkage for the microaggregates usually studied. However, the shrinkage varies since the volume of dried microaggregates was found to be 93 to 99% of their volume when they are saturated. To cite this article: N. Volland-Tuduri et al., C. R. Geoscience 336 (2004).     

Les formations burdigaliennes de Corse orientale dans leur cadre géodynamique

The earliest marine sediments of eastern Corsica, linked to the birth of the Corsica Basin, are represented by granitic breccia of the Saint-Antoine Formation and pelagic marls of the Alzelle Formation. They are dated as Mid-Burdigalian by nannoplankton and planktonic foraminifera (relative age and grade datings between 18.7 and 18.3 Ma). The Aghione Formation (Latest Burdigalian–Langhian) lies upon the Alzelle Formation. A component of the major East-Corsican faults, the Saint-Antoine Fault, underwent extensional activity during the Burdigalian and until the Late Miocene, when occurred the uplift of the Castagniccia antiform. To cite this article: M.-D. Loÿe-Pilot et al., C. R. Geoscience 336 (2004).     

Contexte de mise en place des roches basiques de la ceinture de roches vertes birimienne de Diagorou-Darbani (Liptako,Niger, Afrique de l'Ouest) : plateau océanique ou environnement d'arc/bassin arrière-arc océanique

The Diagorou-Darbani Birimian greenstone belt includes (i) tholeiitic metabasalts with flat to slightly depleted LREE patterns, (ii) amphibolites having high contents in both compatible and incompatible elements with strongly fractionated spidergrams showing large HFSE negative anomalies, and (iii) metabasalts and amphibolites with intermediate features between the two previous groups. The chemical compositions of these rocks are not those of oceanic plateau basalts, but suggest a magmatic evolution from an arc environment to a back-arc oceanic basin. Source of the highly enriched amphibolites could be a depleted mantle metasomatized by slab-derived siliceous melts. To cite this article: A. Soumaila et al., C. R. Geoscience 336 (2004).     

Les surfaces boisées à l'échelle de la planète : usages conjoints pour la séquestration du carbone et la production d'énergie

The role of forest ecosystems in the regulation of greenhouse effect at the global scale is developed here, from two points of view, sometimes considered as opposed: carbon storage and wood production for energy. A nomenclature is proposed to understand all the various mechanisms implied in carbon storage. A comparison is made between the effects on carbon emissions of storage alone and storage with wood fuel production. Use of wood energy is proved to be a ‘bonus’ that could optimise, in the middle and long terms, the use of fossil fuel reserves. To cite this article: A. Prieur et al., C. R. Geoscience 336 (2004).     

Neoformation of Ni phyllosilicate upon Ni uptake on montmorillonite: A kinetics study by powder and polarized extended X-ray absorption fine structure spectroscopy

Wet chemistry kinetics and powder and polarized extended X-ray absorption fine structure (EXAFS and P-EXAFS) spectroscopy were combined to investigate the mechanism of Ni uptake on montmorillonite, at pH 8, high ionic strength (0.2 M Ca(NO₃)₂), initial Ni concentration of 660 μM, and solid concentration of 5.3 g/L. Approximately 20% of Ni sorbed within the first 24 h; thereafter, the Ni uptake rate slowed, and 12% of the initial Ni concentration remained in solution after 206 d of reaction time. Powder EXAFS spectra collected on wet pastes at 1, 14, 90, and 206 d showed the presence of Ni-Ni pairs at ∼3.08 Å in an amount that gradually increased with time. Results were interpreted by the nucleation of a Ni phase having either an α-Ni-hydroxide- or a Ni-phyllosilicate-like local structure. The latter possibility was confirmed by recording P-EXAFS spectra of a highly textured, self-supporting montmorillonite film prepared in the same conditions as the wet samples and equilibrated for 14 d. The orientation distribution of the c*-axes of individual clay particles off the film plane, as measured by quantitative texture analysis, was 32.8° full width at half maximum, and this value was used to correct from texture effect the effective numbers of Ni and Si nearest neighbors determined by P-EXAFS. Ni atoms were found to be surrounded by 2.6 ± 0.5 Ni atoms at 3.08 Å in the in-plane direction and by 4.2 ± 0.5 Si atoms at 3.26 Å in the out-of-plane direction. These structural parameters, but also the orientation and angular dependence of the Ni and Si shells, strongly support the formation of a Ni phyllosilicate having its layers parallel to the montmorillonite layers. The neoformation of a phyllosilicate on metal uptake on montmorillonite, documented herein for the first time, has important geochemical implications because this dioctahedral smectite is overwhelmingly present in the environment. The resulting sequestration of sorbed trace metals in sparingly soluble phyllosilicate structure may durably decrease their migration and bioavailability at the Earth’s surface and near surface.     

Structures of quartz (100)- and (101)-water interfaces determined by x-ray reflectivity and atomic force microscopy of natural growth surfaces

The structures of prismatic (100) and pyramidal (101) growth faces of natural quartz crystals, and their modification upon annealing at T ≤ 400°C were investigated ex situ by atomic force microscopy (AFM) and in water by high-resolution X-ray reflectivity. AFM images revealed the presence of ∼ 0.1 to 1 μm-wide flat terraces delimited by steps of one to several unit cells in height. These steps follow approximately directions given by the intersection of growth faces. Modeling of X-ray reflectivity data indicates that surface silica groups on flat terraces have only one free Si-O bond each (presumably hydroxylated), except for some having two free Si-O bonds observed on a single (100) surface. Vertical relaxation of atomic positions (< 0.4 Å for terminal oxygens and < 0.2 Å for silicon and oxygen atoms fully coordinated to structural tetrahedra) is limited to a depth of 14 Å. Electron density profiles for all measured interfaces are consistent with a single layer of adsorbed water, with no evidence for additional organization of water molecules into distinct layers extending into the bulk solution. Similar interfacial structures were observed for natural and annealed surfaces of identical crystallographic orientation, indicating that extensive reconstruction of the silica network at the quartz surface did not occur under the annealing conditions.