Earthquake-induced landslide prediction using back-propagation type artificial neural network: case study in northern Iran

Natural Hazards - Landslides can cause extensive damage, particularly those triggered by earthquakes. The current study used back propagation of an artificial neural network (ANN) to conduct risk...     

Geochemical effects of oxidation products and framboidal pyrite oxidation in acid mine drainage prediction techniques

Acid mine drainage predictive testwork associated with the Australian Mineral Industries Research Association (AMIRA) P387A Project: Prediction and Kinetic Control of Acid Mine Drainage (AMD) has critically examined static acid assessment and kinetic information from acid–base accounting techniques, including net acid production potential (NAPP), net acid generation (NAG) and column leach tests. This paper compares results on two waste rock samples that were obtained from the Kaltim Prima Coal mine (KPC) containing significant quantities of fine-grained framboidal pyrite. In agreement with other research, the authors' results indicated that framboidal pyrite is more reactive than euhedral forms due to the greater specific surface area of framboidal pyrite. This is evidenced by optical microscopy of reacted samples. Importantly, the results showed that NAPP testing is biased by the rapid acid generating oxidation of framboidal pyrite prior to, and during the acid neutralisation capacity (ANC) test. This can result in negative ANC values for samples containing significant framboidal pyrite (often “corrected” to zero kg H₂SO₄/t) when significant ANC is actually present in the sample. NAG testing using H₂O₂ indicated that samples containing a significant quantity of framboidal pyrite can result in the catalytic decomposition of the H₂O₂ prior to complete oxidation of the sulfide minerals present, requiring sequential addition of H₂O₂ for completion. A benefit of the NAG test, however, is that it assesses the net acid generation capacity of the sample without bias towards acid generation as is observed using NAPP methods. The kinetic NAG test also gives information on the reaction sequence of framboidal and euhedral pyrite. Periodic (kinetic) analysis of sub-samples from column leach tests indicated rapid oxidation of the framboidal pyrite compared to the euhedral pyrite, which was correlated with the greater framboidal pyrite surface area.Calculations to determine the sulfide/sulfate acidity derived from the oxidation of framboidal pyrite prior to; and during the ANC test have been developed to provide a better indication of the actual ANC (ANC_Actual) of the sample. Paste pH values of <pH 4–5 may be one suitable trigger mechanism for the implementation of this new method. This has led to an improved NAPP estimation of total acid production. Together with NAG and column leach testing this improved methodology has resulted in accurate AMD characterisation of samples containing acidic oxidation products and framboidal pyrite.     

Long-term evolution of the spin of Venus: II. numerical simulations

We present here the numerical application of the theoretical results derived in Correia et al. (2003, Icarus 163, 1-23) for the spin evolution of Venus since its formation. We explore a large variety of initial conditions to cover the possible formation and evolutionary scenarios. In particular, we pay special attention to the evolutions which cross the chaotic zone resulting from secular planetary perturbations (Laskar and Robutel, 1993, Nature 361, 608-612). We demonstrate that Venus’ axis can be temporarily trapped in a secular resonance with the node of Neptune’s orbit, which can prevent it from being tilted to 180° and will drive it toward 0°. We test several dissipation models and parameters to evaluate their contribution to the planet’s spin history. We confirm that despite the variations in the models, only three of the four final spin states of Venus are possible (Correia and Laskar, 2001, Nature 411, 767-770) and that the present observed retrograde spin state of Venus can be attained by two different processes. In the first scenario (π−), the axis is tilted toward 180° while its rotation rate slows down, while in the second one, the axis is driven toward 0° obliquity and the rotation rate decreases, stops, and increases again in the reverse direction to a final equilibrium value (0−).     

S-wave Velocity Models in the Scotia Sea Region, Antarctica, from Nonlinear Inversion of Rayleigh Waves Dispersion

—More than 60 events recorded by four recently deployed seismic broadband stations around Scotia Sea, Antarctica, have been collected and processed to obtain a general overview of the crust and upper mantle seismic velocities.¶Group velocity of the fundamental mode of Rayleigh waves in the period between 10 s to 30–40 s is used to obtain the S-wave velocity versus depth along ten different paths crossing the Scotia Sea region. Data recorded by two IRIS (Incorporated Research Institutions for Seismology) stations (PMSA, EFI) and the two stations of the OGS-IAA (Osservatorio Geofisico Sperimentale—Instituto Antarctico Argentino) network (ESPZ, USHU) are used.¶The Frequency-Time Analysis (FTAN) technique is applied to the data set to measure the dispersion properties. A nonlinear inversion procedure, "Hedgehog," is performed to retrieve the S-wave velocity models consistent with the dispersion data.¶The average Moho depth variation on a section North to South is consistent with the topography, geological observations and Scotia Sea tectonic models.¶North Scotia Ridge and South Scotia Ridge models are characterised by similar S-wave velocities ranging between 2.0 km/s at the surface to 3.2 km/s to depths of 8 km/s. In the lower crust the S-wave velocity increases slowly to reach a value of 3.8 km/s. The average Moho depth is estimated between 17 km to 20 km and 16 km to 19 km, respectively, for the North Scotia Ridge and South Scotia Ridge, while the Scotia Sea, bounded by the two ridges, has a faster and thinner crust, with an average Moho depth between 9 km and 12 km.¶On other paths crossing from east to west the southern part of the Scotia plate and the Antarctic plate south of South Scotia Ridge, we observe an average Moho depth between 14 km and 18 km and a very fast upper crust, compared to that of the ridge. The S-wave velocity ranges between 3.0 and 3.6 km/s in the thin (9–13 km) and fast crust of the Drake Passage channel. In contrast the models for the tip of the Antarctic Peninsula consist of two layers with a large velocity gradient (2.3–3.0 km/s) in the upper crust (6-km thick) and a small velocity gradient (3.0–4.0) in the lower crust (14-km thick).     

Chlorine-bearing lizardite from metakimberlite of the Udachnaya-East pipe,northern Yakutia

Doklady Earth Sciences -     

Occurrence and geochemistry of arsenic in the groundwater of Eastern Croatia

In order to examine the extent of the As enrichment and the factors influencing this enrichment in the groundwater of Eastern Croatia, groundwater samples were collected from 56 production wells in two counties, Osijek-Baranja and Vukovar-Srijem, suspected to be more affected. Hydrochemical analyses were performed at all locations including in situ As speciation at 32 locations. Arsenic was detected in 46 out of 56 groundwater samples with total As concentrations up to 491 μg/L. Thirty-six of the studied wells yielded groundwater with total As concentrations that exceeded the WHO Maximum Contaminant Level for arsenic in drinking water of 10 μg/L. Only inorganic As species were detected with arsenite As(III) as the predominant form. The spatial distribution of As in the groundwater was significantly linked with geological, geomorphological and hydrogeological development of the alluvial basin of the Drava and Sava rivers. The most probable groundwater As sources are deeper sediments from the Middle and Upper Pleistocene. The results obtained suggest that biogeochemical processes controlling As concentration in the groundwater are complex and location-specific. Reductive dissolution of Fe oxides, desorption of As from Fe oxides and/or clay minerals as well as competition for the sorption sites with organic matter and phosphate could be the principal mechanisms that control As mobilization. The extent of those processes vary in the different parts of the Drava and Sava depressions and could be linked to different site related parameters, such as lithology, mineralogy, local hydrology and hydrogeology; thus different processes of As mobilization have been proposed for the different types of water in relation to groundwater evolution.     

On the stress state of the Sakhalin crust according to the data of drilling deep boreholes

The stress state of the sedimentary rocks in the oil-and-gas fields of Sakhalin is estimated and analyzed; data from exploratory boreholes in the eastern Pacific (San-Andreas fault zone) are considered. The vertical and limiting horizontal stresses are calculated for different depths. The maximum sublateral compression can exceed the vertical stress by a factor of 1.2–4 on average in northern and southern Sakhalin. It is shown that the limiting horizontal stress and the maximum shear stress grow as the depth increases.     

Sedimentary formations and main development stages of the western Transbaikal and southeastern Baikal regions in the late Cretaceous and Cenozoic

Upper Cretaceous and Cenozoic formations of the western Transbaikal and southeastern Baikal regions are considered. Molasses and molassoids (molasse-type sediments) were included into these formations in previous works. In our opinion, the following formations are developed in these regions: plain fan formation divided into the terrigenous (Upper Cretaceous) and coaliferous (Upper Oligocene-Lower Pliocene) subformations; plain fine-clastic formation (Paleogene, except the Upper Oligocene); and orogenic molasse formation (Upper Pliocene-Holocene) divided into the lower red-colored and upper gray-colored subformations. Main textural features of these formations are considered. Paleogeographic and paleotectonic settings of their accumulation are reconstructed. It is shown that coarse-clastic sediments of fan formations accumulated in grabens among ancient denudation plains due to the destruction of rocks in near-wall benches. These plains probably hosted in some areas remnants of the mountainous relief. Origination and development of the Baikal rift zone was the main geological event in the Baikal region during the Late Cretaceous and Cenozoic. Based on study of the southeastern Baikal region with the thickest and most representative Cenozoic sections, the prerifting and rifting stages of this zone and correlative events in the adjacent (relatively stable) areas of the western Transbaikal region are characterized.     

Dielectric constants of tephroite,fayalite and olivine and the oxide additivity rule

The dielectric constants and dissipation factors of synthetic tephroite (Mn₂SiO₄), fayalite (Fe₃SiO₄) and a forsteritic olivine (Mg_1.80Fe_0.22SiO₄) were measured at 1 MHz using a two-terminal method and empirically determined edge corrections. The results are: tephroite, κ′_a= 8.79 tan δ_a = 0.0006 κ′_b = 10.20 tan δ_b = 0.0006 κ′_c= 8.94 tan δ_c= 0.0008 fayalite, gk′_a = 8.80 tan δ_a = 0.0004 gk′_b= 8.92 tan δ_b = 0.0018 gk′_c = 8.58 tan δ_c = 0.0010 olivine, gk′_a = 7.16 tan δ_a = 0.0006 gk′_b = 7.61 tan δ_b = 0.0008 gk′_c = 7.03 tan δ_c = 0.0006 The low dielectric constant and loss of the fayalite indicate an exceptionally low Fe³⁺ content. An FeO polarizability of 4.18 ų, determined from α_D(FeO) = [α_D (Fe₂SiO₄)-α_D(SiO₂)]/2, is probably a more reliable value for stoichiometric FeO than could be obtained from Fe_xO where x = 0.90–0.95. The agreement between measured dielectric polarizabilities as determined from the Clausius-Mosotti equation and those calculated from the sum of oxide polarizabilities according to α_D(M₂M′X₂) = 2α_D(MX) + α_D(M′X₂) is ～+2.8% for tephroite and +0.2% for olivine. The deviation from additivity in tephroite is discussed.     

Galaxies in Observations and Numerical Models

Astronomy Reports - A comparison of the virial parameters of galaxies and galaxy clusters (radius, density, and entropy function) in a wide range of masses, $${{10}^{6}} \leqslant...