Leaching of Lisan Marl and its consequences on the engineering behavior of dikes,studied by finite elements modeling

Leaching of Lisan Marl, Dead Sea, Jordan increased the soil compressibility and cohesion intercept. Back analysis using the Plaxis finite element code was successfully implemented. The Finite element modeling of dike construction showed a significant increase of total settlement and negligible effect on the strength as calculated by the φ/c reduction method. The height of dikes to be constructed on Lisan Marl as foundation material, should be optimized to account for the effect of soluble salts leaching. For this to take place, an accurate calculation of settlement is crucial.     

Source geometry and mechanism of 1978 Tabas, Iran, earthquake from well located aftershocks

Aftershocks of the September 16, 1978 Tabas earthquake located from close-in observations made during a four-week fielding of temporary stations have been analyzed for the purpose of delineating detailed source geometry of the 1978 earthquake. Spatial distribution of aftershocks and their composite focal mechanism suggest that the geometry of faulting is far from planar. Aftershocks define two prominent alignment. The southern alignment strikes E-W to WNW-ESE, whereas the northern alignment strikes in a N-S to NNW-SSE direction with an abrupt change of nearly 55–60 degrees near 33.4°N latitude. Both field observations of surface faulting pattern and systematic variation of principal directions of stress axes computed from aftershock focal mechanisms are consistent with the upthrusting and imbrication of a wedge shaped crustal block with the wedge angle of about 120 degrees. Both geological and seismological evidence suggest that the deformed zone is truncated at the southern edge by preexisting E-W fault structures. New observations may provide a partial answer to the unexplained farfield asymmetry of the long period Rayleigh wave radiation pattern recently observed for the mainshock across IDA network.     

Potential impact of climate change on durum wheat cropping in Tunisia

The potential effect of climate change on durum wheat in Tunisia is assessed using a simple crop simulation model and a climate projection for the 2071–2100 period, obtained from the Météo-France ARPEGE-Climate atmospheric model run under the IPCC (International Panel on Climate Change) scenario A1B. In the process-oriented crop model, phenology is estimated through thermal time. Water balance is calculated on a daily basis by means of a simple modelling of actual evapotranspiration involving reference evapotranspiration, crop coefficients and some basic soil characteristics. The impact of crop water deficit on yield is accounted for through the linear crop-water production function developed by the FAO (Food and Agriculture Organization of the United Nations). Two stations are chosen to study the climate change effect. They are representative of the main areas where cereals are grown in Tunisia: Jendouba in the northern region and Kairouan in the central region. In the future scenario, temperature systematically increases, whereas precipitation increases or decreases depending on the location and the period of the year. Mean annual precipitation declines in Jendouba and raises in Kairouan. Under climate change, the water conditions needed for sowing occur earlier and cycle lengths are reduced in both locations. Crop water deficit and the corresponding deficit in crop yield happen to be slightly lower in Kairouan; conversely, they become higher in Jendouba.     

Distance scaling of vertical and horizontal response spectra of the Loma Prieta earthquake

Attenuations of the vertical and horizontal response spectra of the 17 October 1989 Loma Prieta, California, earthquake are developed through analyses of the ground motion at 53 sites within a 100 km radius of the source. The analyses are performed on the spectral ordinates for 16 incremental periods ranging from 0.05 to 2.0 sec. The response spectra are modelled empirically for two different site conditions characterized by rock and stiff-soil geologies. Data analysis is performed by the application of a non-linear multivariate regression procedure allowing for distance and site factor as independent variables. Variation of the vertical-to-horizontal (V/H) spectral ratios with wave frequency and distance shows the same behaviour as observed previously in the widely separated geographic regions of northeastern Taiwan and east-central Iran. The predicted ratios at sites underlain by stiff soil are generally higher than the commonly used value of 2/3 at high frequencies ( > 5 Hz) in the near-source region (R < 30 km), but reduce to 1/2 or less at longer periods and farther distances. This behaviour is also observed at rock sites; however, it is somewhat less pronounced. With a faster attenuation of spectral ordinates at higher frequencies, the shape of the response spectrum is found to change with distance. As expected, the spectral attenuation with distance is generally higher for the vertical spectrum than for the horizontal spectrum. The difference is particularly significant at the higher-frequency end of spectrum. Site amplification factors for stiff soil with respect to rock geology varies between 1.17 and 1.72 for horizontal spectrum and 1.01 and 1.81 for vertical spectrum. Spectral amplifications at four sites underlain by soft soil and artificial fill, are also evaluated. This is done by a comparison of the observed spectra with those predicted for rock geology at corresponding distances. As expected, the resulting amplification factors at soft-soil sites show significant increase relative to those at sites underlain by rock.     

Will autogenic succession be sufficient to recover from vegetation cover loss or will soil condition need to be addressed in the arid lands of Kuwait?

Intervention is often required for the restoration of damaged arid ecosystems, particularly when the base environmental conditions are no longer suitable for autogenic recovery. Umm Nigga, in Kuwait, was damaged by overgrazing and destructive camping. It is unclear whether its restoration will require remediation of the soil conditions, or whether autogenic succession can occur once the area is fenced and released from this pressure. Thus, in this project, we assessed the current condition of the site by collecting soil samples and vegetation assessment within each ecosystem and determined suitable locations for the re-vegetation of native seeds and seedlings using geographical information system. Our results showed that the vegetation in the coastal portions of the ecosystem was not damaged. However, in the desert ecosystem locations, vegetation cover was very low and composed of very few species in the damaged areas but still, most soil nutrients were in supply similar to that in the control areas. We conclude that soil remediation and re-vegetation are, likely, not necessary to restore the damaged sites in any of these ecosystems. Rather, fencing alone will probably release the ecosystem. With these sites as a model, a conceptual framework is presented for arid ecosystem assessment and restoration planning.     

Interpretation of some magnetic bodies using neural networks inversion

Magnetic surveys have been used for mineral exploration where different data processing techniques were used to derive the parameters of causative targets. In this respect, the neural network (NN) technique was used to estimate the magnetic causative target parameters. Examples of NN inversion have been tested on synthetic examples where the NN was trained well using forward models of the vertical magnetic effect of a vertical sheet and a horizontal circular cylinder. Specifically, modular neural network (MNN) inversion has been used for the parameter estimation of the causative targets, where the sigmoid function was used as the activation function. The effect of random noise and the error estimation of the horizontal location have been analyzed. When NN is applied to real data, it estimates successfully the parameters of the causative targets such as burial depths, magnetic constants, and angle of polarization. Hilbert transform has been used to locate the source origin, which is important for the NN inversion. This approach has more advantages than the conventional data inversions in terms of its efficiency and flexibility. It also gives fast solutions. The MNN approach has been applied to the Kursk and Manjampalli anomalies, where the results were shown to be in good agreement with the other techniques published in the literature.     

Development of A Three-Dimensional Guidance System for Long-Range Maneuvering of A Miniature Autonomous Underwater Vehicle

The present paper introduces a three-dimensional guidance system developed for a miniature Autonomous Underwater Vehicle（AUV）. The guidance system determines the best trajectory for the vehicle based on target behavior and vehicle capabilities. The dynamic model of this novel AUV is derived based on its special characteristics such as the horizontal posture and the independent diving mechanism. To design the guidance strategy, the main idea is to select the desired depth, presumed proportional to the horizontal distance of the AUV and the target. By connecting the two with a straight line, this strategy helps the AUV move in a trajectory sufficiently close to this line. The adjacency of the trajectory to the line leads to reasonably short travelling distances and avoids unsafe areas. Autopilots are designed using sliding mode controller. Two different engagement geometries are considered to evaluate the strategy＇s performance： stationary target and moving target. The simulation results show that the strategy can provide sufficiently fast and smooth trajectories in both target situations.     

Neuro-fuzzy modeling based genetic algorithms for identification of geochemical anomalies in mining geochemistry

A genetic algorithm (GA)-based neuro-fuzzy approach is used for identification of geochemical anomalies by implementing a Takagi, Sugeno and Kang (TSK) type fuzzy inference system in a 5-layered feed-forward adaptive artificial neural network. This paper investigates the effectiveness of GA-based neuro-fuzzy for separating zone dispersed mineralization (ZDM) from blind mineralization, and its application for identification of geochemical anomalies in the arid landscape of the Lut metallogenic province in eastern Iran. Other classification algorithms such as metallometry, zonality, criteria, and back-propagation artificial neural network classifiers are also used for comparison. The genetic operators are carefully designed to optimize the artificial neural network, avoiding premature convergence and permutation problems. The results show that the GA-based hybrid neuro-fuzzy model can provide accurate results in comparison with those results obtained by other techniques. Neuro-fuzzy and GA-based neuro-fuzzy techniques appear to be well-suited for routine exploration geochemistry applications. In conjunction with statistics and conventional mathematical methods, hybrid approaches can be developed and may prove a step forward in the practice of applied geochemistry.     

Apatite fission track analysis in the Argentera massif: evidence of contrasting denudation rates in the External Crystalline Massifs of the Western Alps

Apatite fission track dating from a central transect in the Argentera massif (southernmost External Crystalline Massif = ECM) yielded ages between 8.05 ± 0.6 and 2.4 ± 0.2 Myr, with a positive age/altitude correlation above 3 Ma, 1200 m. Recognising a thermal peak at c . 250°C, 33 Ma, based on stratigraphic, metamorphic and ³⁹Ar/⁴⁰Ar data, the present results suggest a slow cooling rate (8–5°C) for the Argentera massif during the Oligocene–early Pliocene. This rate compares with that from the Pelvoux massif, but contrasts with those observed in the northern ECM (Mont-Blanc and Aar: up to 14°C Myr⁻¹) for the same time interval. This can be related to the different location of the ECM within the collided European margin. At about 3–4 Ma, the denudation rate would have increased up to c . 1 mm yr⁻¹ in the Argentera massif, reaching the same value as in the Belledonne and northern ECM, likely a consequence of Penninic thrust inversion.