The thermal state of the Venusian mantle

Assuming that the surface topography of the Ovda and Thetis plateaus, and that of the saddle region between Thetis and Atla plateaus, is due to surface subsidence of oceanic-type thermal boundary layers, we calculated the temperature at 200 km beneath the plateaus to be about 1600 C, and that beneath the saddle region to be about 1400–1500 C. The total subsidence of Ovda plateau in the last 3/4 of its existence, i.e. between 200 km and 800 km off the postulated ridge axis, suggests that the plateau is probably a young feature, less than 40 m.y. old. The spreading plate models imply a half-spreading rate of 2.3–5.3 cm/yr for the plateaus and 2–2.8 cm/yr for the saddle region.     

EXPERIMENTAL AND FIELD STUDY ON MINING-PIT MIGRATION

1 INTRODUCTION Because of the large quantity of sand and gravel in their beds, rivers have always been considered as a major source of sand and gravel for civil works. Acceptable quality, ease of extraction and economy are some of the reasons could be mentioned. Unfortunately, specific laws and regulations regarding the safe in-stream mining have not been provided for users and officials. What should be taken into account are the effects of over-mining of sand and gravel, which can cause …     

Numerical ANFIS-Based Formulation for Prediction of the Ultimate Axial Load Bearing Capacity of Piles Through CPT Data

This study explores the potential of adaptive neuro-fuzzy inference systems (ANFIS) for prediction of the ultimate axial load bearing capacity of piles (P_u) using cone penetration test (CPT) data. In this regard, a reliable previously published database composed of 108 datasets was selected to develop ANFIS models. The collected database contains information regarding pile geometry, material, installation, full-scale static pile load test and CPT results for each sample. Reviewing the literature, several common and uncommon variables have been considered for direct or indirect estimation of P_u based on static pile load test, cone penetration test data or other in situ or laboratory testing methods. In present study, the pile shaft and tip area, the average cone tip resistance along the embedded length of the pile, the average cone tip resistance over influence zone and the average sleeve friction along the embedded length of the pile which are obtained from CPT data are considered as independent input variables where the output variable is P_u for the ANFIS model development. Besides, a notable criticism about ANFIS as a prediction tool is that it does not provide practical prediction equations. To tackle this issue, the obtained optimal ANFIS model is represented as a tractable equation which can be used via spread sheet software or hand calculations to provide precise predictions of P_u with the calculated correlation coefficient of 0.96 between predicted and experimental values for all of the data in this study. Considering several criteria, it is represented that the proposed model is able to estimate the output with a high degree of accuracy as compared to those results obtained by some direct CPT-based methods in the literature. Furthermore, in order to assess the capability of the proposed model from geotechnical engineering viewpoints, sensitivity and parametric analyses are done.     

Stress differences in the moon as an evidence for a cold moon

Assuming that the lateral variations of density in the lunar crust, the crustal density anomalies, are responsible for the lateral undulations of the lunar gravitational potential, we compute these anomalies for four different lunar models, which include an entirely solid Moon and three different solid lunar models with partially molten layers located within 600 km depth. The stress differences created by the density anomalies are determined for these models. It is found that, since the formation of the mascons, the entirely solid lunar model should have supported stress differences of the order of 70 bars while in the case of the other models, the solid layer overlying the partially molten one should have supported stress differences of more than 100 bars. The high stress differences associated with the partially molten models lead us to conclude that these models are not proper ones, and thus the Moon has always been solid since the formation of the mascons. Lunar Science Institute Contribution No. 97. The research in this paper was done while the author was a Visiting Scientist at the Lunar Science Institute, which is operated by the Universities Space Research Association under Contract No. NSR 09-051-001 with the National Aeronautics and Space Administration.     

Early Cretaceous sedimentary provenance and structural evolution of the central Sanandaj–Sirjan Zone,Iran: implications for palaeogeographic reconstructions of the northern Neo-Tethyan margin

ABSTRACT

The Early Cretaceous was an important epoch in the evolution of the Earth system in which major tectonic episodes occurred, especially along the Alpine–Himalayan belt. The paucity of reliable palaeogeographic data from the central segment of this geological puzzle, however, hampers the reconstruction of a panoramic view of its Early Cretaceous palaeogeography and geodynamic setting. Here we present multidisciplinary provenance data from Lower Cretaceous strata of the overriding plate of the Neo-Tethyan subduction zone (the Sanandaj–Sirjan Zone; SSZ, of central Iran), including structural, basin-fill evolution, petrographic and geochemical analyses. Sandstone provenance analysis of Lower Cretaceous red beds suggests the occurrence of sub-mature litho-quartzose sandstones attributed to an active continental arc margin in convergent setting predominantly derived from plutonic, quartzose sedimentary and metamorphic rocks exposed in the central SSZ. Weathering indices indicate moderate chemical weathering in the source area which may be related to close source-to-sink relationships or arid climate. Our palaeogeographic reconstructions and original geological mapping indicate that the erosion of uplifted basement rocks exposed in horst blocks provided the sediment sources for the syn-extensional deposition of uppermost Jurassic–lowermost Cretaceous conglomerates and Lower Cretaceous siliciclastic red beds within a continental retro-arc basin during initiation of the ‘Neo-Tethys 2?. The polyphase tectonic reactivation along the principal fault of the study area controlled the syn- and post-extensional tectonostratigraphic evolution that reflect the corresponding mechanical decoupling/coupling along the northern Neo-Tethyan plate margin.     

Parkfield,California, Earthquake of June 1966: Interpretation of the strong motion records

A detailed seismological interpretation of the strong motion records was attempted for the 1966 Parkfield earthquake, California. Velocity and displacement traces integrated from the corresponding recorded accelerograms were found most valuable in studying the earthquake mechanism and wave forms. A double-couple right-lateral strike — slip mechanism (along the San Andreas fault) is consistent with the recorded direct S-waves originating from the hypocentre. High energy arrivals observed on the velocity traces are interpreted as S-waves (‘stopping phases’) that originated at the termination of the rupture towards the south-east of the San Andreas fault. A double-couple left-lateral strike–slip mechanism is suggested as the cause of this rupture termination. From particle velocity diagrams of the stopping phases in the horizontal plane, the rupture length was found to be between 20 and 28 km. Corresponding rupture velocities are estimated to be 2·5 ± 0·1 and 3·1 ± 0·5 km/s. The inference from the strong motion records is that Love waves were more excited at the south-western than the north-eastern side of the fault, whereas the Rayleigh waves were more energetic at the north-eastern than the south-western side of the fault.     

Unruh’s detector in the presence of Lorentz symmetry breaking

We investigate the quantum field theory of a Lorentz non-invariant model with a massive nonlinear dispersion relation in Minkowski space. The model involves some non-causal signals in the form of wave packets propagating with super-luminal group velocities. To avoid the problems with causality we characterize the causal sector of the theory by a cutoff condition excluding all super-luminal group velocities. It is argued that in the causal theory satisfying the energy positivity condition an Unruh’s detector moving with a constant velocity with respect to the preferred frame does not detect any particle. But in a causal theory violating energy positivity, detection of a field quanta occurs. We comment on the origin of this particle creation.     

New developments with design and construction of a thermal/vacuum qualified photogrammetric system

In the frame of the development of a photogrammetric system to be used in thermal/vacuum chambers at the European Space Research and Technology Centre (ESTEC) of European Space Agency (ESA) and other sites across Europe, the design of a network using micro-cameras was specified by ESA-ESTEC. A thermal/vacuum qualified photogrammetric system, which is able to work and acquire images in vacuum and at cryo-temperatures, was constructed by ESA-ESTEC Test Centre Division. The current system uses four space qualified one-mega pixel cameras and is able to measure large space structures in vacuum and at temperatures down to ?170 ^°C with a global accuracy better than 1 part per 100,000 in object space. Several tests aiming at the qualification of the sensors and system in terms of operation and accuracy have been carried out. Special measures have been developed and special attention has been taken into account specifically for the first application of the photogrammetric system. It is to verify the ESA’s Herschel Telescope Flight Model alignment positioning.     

PROMETHEE II and fuzzy AHP: an enhanced GIS-based landslide susceptibility mapping

This paper describes the application of a well-known multi-criteria decision-making technique, called preference ranking organization method for enrichment evaluation (PROMETHEE II), in combination with fuzzy analytical hierarchy process (FAHP), as a weighting technique to explore landslide susceptibility mapping (LSM). To this end, eight landslide-related geodata layers of the Minoo Dasht located in the Gorgan province of Iran, involving slope, aspect, distance to river, drainage density, distance to fault, mean annual rainfall, distance to road and lithology have been integrated using the PROMETHEE II enhanced by FAHP technique. Afterward, the receiver operating characteristics (ROC) curves for the proposed LSM were drawn using an inventory of landslides containing 83 recent and historic landslide points, and the area under curve = 0.752 value was calculated accordingly. Additionally, to further verify the practicality of such susceptibility map, it was also evaluated against the landslide inventory using simple overlay. The outcome was that about 11 % of the occurred landslide points fall into the very high susceptibility class of the LSM, but approximately 52 % of them indeed fall into the high and very high susceptibility zones together. Also, it resulted that no recorded landslide occurred in the zone of very low susceptibility. According to the results of the ROC curves analysis and simple overlay evaluation, the produced map has exhibited good performance.