The Ni–Antimonide Mineral Assemblage: A Product of Recrystallization of Sn–Pb–Zn Ores of the Yuzhnoe Deposit,Sikhote-Alin,Russia

Doklady Earth Sciences - A mineral assemblage with nisbite NiSb2 and breithauptite NiSb unique for a Mesozoic (Sn)–Pb–Zn vein deposit is found during mineralogical–geochemical...     

Abundance and distribution of ichthyoplankton in Narragansett Bay, Rhode Island, 1989–1990

An ichthyoplankton survey (18 stations in seven sampling sectors) was conducted in Narragansett Bay in 1990 to provide information on abundance, distribution, and seasonal occurrence of eggs and larvae of estuarine fishes, including seasonal migrants. An additional goal was to examine changes in species composition, abundance, and distribution occurring since the last baywide survey in 1972–73. The taxonomic composition of eggs and larvae in 1990 (41 species in 25 families from 684 plankton samples) and in 1972–73 (43 species in 28 families from 6900 samples) was similar. Maximum abundance of fish eggs occurred in June and larvae in July, minimum abundance in September to February. Species diversity was greatest in May–July and lowest during January in both surveys. However, egg and larval densities in 1990 were considerably lower than in 1972–73. Bay anchovy, tautog, and cunner accounted for 86% of the eggs and 87% of the larvae in the bay in 1990. These three species accounted for only 55% of the eggs and 51% of the larvae in 1972–73, with menhaden accounting for another 18% of the eggs and 34% of the larvae. Searobins, scup, and butterfish eggs were common in 1973 (19%) but rare in 1990 (2%). Ichthyoplankton abundance for several of the most abundant species was significantly lower (p<0.05) in the Providence River, upper bay, and Greenwich Bay in 1990 than in 1972–73. Density of fish eggs and larvae in the lower portions of the bay was lower in 1990 for some species but not others. Distribution data suggested a general down-bay shift in density in 1990. *** DIRECT SUPPORT *** A01BY085 00015     

Two stages of high-pressure metamorphism in the Main Uralian Fault area (northern Urals)

Metamorphism in the northern sector of the Main Uralian Fault (MUF) area, northern Urals, is considered by the example of the Salatim glaucophane-schist and Belokamenka kyanite-staurolite complexes. New isotope-geochronological dates for metamorphic rocks of the MUF area are presented. The obtained data evidence the existence of two metamorphic events, of Early and Late Devonian ages, which apparently correspond to the wedging-up of subduction paleozones.     

Tectonic evolution of the Siberian Platform during the Vendian and Phanerozoic

This paper presents characteristics of the structural regions surrounding the Siberian Platform and discusses the Vendian-present time evolution of the Siberian Paleocontinent with the Siberian Craton making up its nucleus. It shows that the paleocontinent underwent significant intraplate compressional deformations with vertical movements and formation of inversion structural features within broad areas. Such epochs of deformation took place at the Riphean-Vendian time boundary, during the Late Paleozoic, Late Triassic, Early Cretaceous, and during the Late Cenozoic. The principal rifting events took place during the Middle-Late Devonian. The paper presents paleotectonic reconstructions of East Siberia at several key time intervals.     

Expected peak ground acceleration in Uttarakhand Himalaya,India region from a deterministic hazard model

A method of seismic zonation based on the deterministic modeling of rupture planes is presented. Finite rupture planes along identified lineaments are modeled in the Uttarakhand Himalaya based on the semi empirical technique of Midorikawa (Tectonophysics 218:287–295, 1993). The expected peak ground acceleration thus estimated from this technique is divided into different zones similar to zones proposed by the Bureau of Indian standard, BIS (Indian standards code of practice for earthquake-resistant design of structures, 2002). The proposed technique has been applied to Kumaon Himalaya area and the surrounding region for earthquakes of magnitude M > 6.0. Approximately 56000 km² study area is classified into the highest hazard zone V with peak accelerations of more than 400 cm/s². This zone V includes the cities of the Dharchula, Almora, Nainital, Haridwar, Okhimath, Uttarkashi, Pithorahargh, Lohaghat, Munsiari, Rudraprayag, and Karnprayag. The Sobla and Gopeshwar regions belong to zone IV, where peak ground accelerations of the order from 250 to 400 cm/s² can be expected. The prepared map shows that epicenters of many past earthquakes in this region lie in zone V, and hence indicating the utility of developed map in defining various seismic zones.     

Tsunamis generated by landslides at the coast of conical islands: experimental benchmark dataset for mathematical model validation

This paper presents a new experimental campaign aimed at reproducing tsunamis generated by landslides at the flank of conical islands. In order to describe in high details the wave field around the island a special acquisition system, which consists of both fixed and movable wave gauges, has been employed. Indeed, each experiment has been repeated several times by changing the configuration of the movable gauges, then obtaining a single virtual experiment with high spatial resolution measurements. Fixed run-up gauges measure the waves at fixed locations to statistically quantify the repeatability of the experiments. Selected experimental results are illustrated within the paper that is mainly aimed at defining a benchmark dataset, available on request, for the development/calibration/validation of analytical and numerical models of tsunamis generated by landslides.     

Computation of the seismic stability of rock wedges

Summary Newmark's concept of computing the permanent displacement under seismic loads has been combined with the conventional limit equilibrium analysis to compute the displacements of a rock wedge. The rock wedge formed by the intersecting planes may or may not have a tension crack in the upper slope surface. As the static analysis of a rock wedge is available from the literature, only the seismic problem is treated theoretically in more details.A computer program has been developed to compute the displacements from the digitised input data of the acceleration-time-history. The program can take into account the water pressure on the intersecting planes and on the planes of the tension crack. The effect of rock anchors if present is also taken care of in addition to static surcharge loads. The program calculates the conventional static factor of safety, remaining resistance against sliding, the critical acceleration, exciting force, relative velocity with time and the cumulative displacements.Two model examples are presented: one with simple sinusoidal acceleration and the other one with actual earthquake data considering the different systems of forces acting on the wedge. The results are critically discussed with respect to the different parameters e. g. anchor forces, water pressure and cohesion influencing the magnitude of displacements under seismic loads. It is shown that the critical acceleration is a better index for the seismic stability than the conventional factor of safety.The critical acceleration presented in this paper serves as a very handy tool for a site engineer to get the first hand information about the stability of the wedge for a given acceleration-time-history without going into the details of dynamic analysis.Notations A, B Inclined intersecting planes - C, D Geometric points on the intersection ofA andB - a _cr Critical acceleration - a _h Horizontal acceleration - a _v Vertical acceleration - a _r Relative acceleration of the wedge - DF Driving force - DF _dyn Dynamic driving force - DF _st Static driving force - FS Factor of safety - g Acceleration due to gravity - m Mass of the wedge - RF Resisting force - RF _dyn Dynamic resisting force - RF _st Static resisting force - RS Remaining resisting force against sliding - RS _dyn Total seismic induced force - RS _st Remaining static resisting force against sliding - s _r Cumulative relative displacement of the wedge - TRS Total remaining resisting force against sliding - v _r Relative velocity of the wedge - W Weight of the wedge - W _A ,W _B Weight of the wedge in the planeA andB - Dip of line of intersection of the planesA andB - Average friction angle - _A , _B Friction angle of planeA andB - I, II, III, IV Points in the curve shown in Fig. 6     

Probabilistic compressive strength of sound dry granite

Summary The different functions of cumulative probability of fracture that can be used in the Probabilistic Strength of Materials in the case of constant uniaxial compression are described. Sound fine-grained granite was used to study volume influence by fracturing rectangular prisms, and then no noticeable influence was observed. Since this is showing that all the fracture stresses are belonging to a single set they were included in a single group that exhibited two functions of specific risk of fracture. The population with the lesser fracture stress has no critical zone while the other population does have it and a critical zone in the order of 10^–6 m³ is the minimum size exhibiting a complete fracture of the specimen when the same collapses. All the statistical functions were found to be acceptable according to theX ² criterion.