Imaging of Vp, Vs, and Poisson’s ratio anomalies beneath Kyushu, southwest Japan: Implications for volcanism and forearc mantle wedge serpentinization

We determine detailed 3-D V_p and V_s structures of the crust and uppermost mantle beneath the Kyushu Island, southwest Japan, using a large number of arrival times from local earthquakes. From the obtained V_p and V_s models, we further calculate Poisson’s ratio images beneath the study area. By using this large data set, we successfully image the 3-D seismic velocity and Poisson’s ratio structures beneath Kyushu down to a depth of 150 km with a more reliable spatial resolution than previous studies. Our results show very clear low V_p and low V_s anomalies in the crust and uppermost mantle beneath the northern volcanoes, such as Abu, Kujyu and Unzen. Low-velocity anomalies are seen in the mantle beneath most other volcanoes. In contrast, there are no significant low-velocity anomalies in the crust or in the upper mantle between Aso and Kirishima. The subducting Philippine Sea slab is imaged generally as a high-velocity anomaly down to a depth of 150 km with some patches of normal to low seismic wave velocities. The Poisson’s ratio is almost normal beneath most volcanoes. The crustal seismicity is distributed in both the high- and low-velocity zones, but most distinctly in the low Poisson’s ratio zone. A high Poisson’s ratio region is found in the forearc crustal wedge above the slab in the junction area with Shikoku and Honshu; this high Poisson’s ratio could be caused by fluid-filled cracks induced by dehydration from the Philippine Sea slab. The Poisson’s ratio is normal to low in the forearc mantle in middle-south Kyushu. This is consistent with the absence of low-frequency tremors, and may indicate that dehydration from the subducting crust is not vigorous in this region.     

Determination of the Status of Desertification in the Capital of Mauritania and Development of A Strategy for Combating It

Mauritania, located in the Western Sahara, is one of the least developed countries in the Sahara Desert. Its capital, Nouakchott, which is home to 23% of its population, suffers from soil erosion from the Sahara and saltwater intrusion from the Atlantic Ocean. The local environment is under pressure from the combined effects of climate and socio-economic factors, with desertification being recognized as the greatest threat to life. In this context, high-resolution remote sensing images of Nouakchott obtained during the winters of 1985, 1988, 2000, 2006, and 2010 are selected for interpretation and classification. Analysis of the types of desertification and land use reveals the temporal and spatial characteristics of five distinct time periods from 1985 to 2010. This study analyzes the current status of desertification in Nouakchott and suggests five preventive measures.     

Geotechnical and Environmental Hazards in Desert New Cities: A Case Study of El Minia El Gedida Site,Egypt

The plateau east of the Nile Valley at El Minia, Egypt, has been chosen for the siting of El Minia El Gedida city. Problems of underground caves suggested the need for integral geological, geotechnical and environmental hazard studies to examine the suitability of the area as a building site.Geologically, the area is formed of a thick sequence of Middle Eocene fossiliferous limestones and chalk with some layers of sandy, cherty and marly limestones. These rocks have heterogeneous physical and mechanical properties and fall within the weak to very weak range of limestones. Their mode of failure is almost of the brittle type developing extension, wedge and single shear type fractures. The mechanical properties are controlled by their physical, geological and mineralogical properties. They increase with density and dolomite content and decrease with porosity and calcite content. Empirical equations for some of these relations as well as the relation between field measures of rebound index and compressive strength are presented.Both regional and detailed structural analyses revealed the presence of major and minor normal faults and fractures trending in NW and NE directions. The NW faults are dominant. They define the topographic escarpments in the area. Most of the caves are aligned along major faults of this trend. Faults, fracture distribution and structural hazard maps of the area are presented. Paleostress tectonic analysis of these fractures suggests that the NW and NE faults are extensional due to tectonic stress which changes from normal to parallel to the Red Sea at different geologic times starting in post Middle Eocene. The similarity of this paleotectonic setting to present Red Sea tectonics points out the possibility of future rejuvenation of these faults.Topographically, the area lies in shallow surface drainage basins. The topographical risk is increased by fracturing and it should be considered if the area is subjected to a long period of heavy rainfall. Radiometrically, El Minia El Gedida city represents one of the lowest natural radioactivity areas within the safe limits recommended by the International Commission on Radiological Protection (ICRP).     

Seismic Hazard Estimation in Northern Algeria

In the present study, the seismic hazard in northern Algeria is estimated using both physical strain energy release and Gumbel's extreme values approaches. For six of the most industrial and populated cities in Algeria, seismic hazard is assessed and examined in greater detail. Gumbel's extreme values approach has been used to estimate seismic hazard in terms of magnitude and P.G.A at each point of an equispaced grid all over the north of Algeria. An average attenuation relationship for PGA has been provided using known relations which have been established in regions with similar attenuation characteristics.The results are presented mainly in the form of graphs and contour maps of magnitudes (respectively PGA) with a 60% probability of not being exceeded in the next 100 and 200 years. Globally, they give main features of northern Algeria in terms of zoning (as well as in terms of magnitude and in terms of PGA). They corroborate the ones obtained through other works, especially in the basin areas (Mitidja, Cheliff, Soumam and Constantine Basin).     

General integral operator for radiative transfer problems

General integral operator for radiative transfer problems is considered and will be denoted asK ^k {g(t)}.General theorems for theK-operator valid to any smooth functiong(t) will be established. The effect of the operator to the functions oftenly occur in transfer problems will also be established analytically and computationally.     

Spatial and temporal analysis of the drought vulnerability and risks over eight decades in a semi-arid region (Tensift basin: Morocco)

Theoretical and Applied Climatology - The multiple downscaled scenario products allow us to assess the uncertainty of the variations of precipitation and temperature in the current and future...     

Landslide susceptibility mapping using random forest,boosted regression tree,classification and regression tree,and general linear models and comparison of their performance at Wadi Tayyah Basin,Asir Region,Saudi Arabia

The purpose of the current study is to produce landslide susceptibility maps using different data mining models. Four modeling techniques, namely random forest (RF), boosted regression tree (BRT), classification and regression tree (CART), and general linear (GLM) are used, and their results are compared for landslides susceptibility mapping at the Wadi Tayyah Basin, Asir Region, Saudi Arabia. Landslide locations were identified and mapped from the interpretation of different data types, including high-resolution satellite images, topographic maps, historical records, and extensive field surveys. In total, 125 landslide locations were mapped using ArcGIS 10.2, and the locations were divided into two groups; training (70 %) and validating (25 %), respectively. Eleven layers of landslide-conditioning factors were prepared, including slope aspect, altitude, distance from faults, lithology, plan curvature, profile curvature, rainfall, distance from streams, distance from roads, slope angle, and land use. The relationships between the landslide-conditioning factors and the landslide inventory map were calculated using the mentioned 32 models (RF, BRT, CART, and generalized additive (GAM)). The models’ results were compared with landslide locations, which were not used during the models’ training. The receiver operating characteristics (ROC), including the area under the curve (AUC), was used to assess the accuracy of the models. The success (training data) and prediction (validation data) rate curves were calculated. The results showed that the AUC for success rates are 0.783 (78.3 %), 0.958 (95.8 %), 0.816 (81.6 %), and 0.821 (82.1 %) for RF, BRT, CART, and GLM models, respectively. The prediction rates are 0.812 (81.2 %), 0.856 (85.6 %), 0.862 (86.2 %), and 0.769 (76.9 %) for RF, BRT, CART, and GLM models, respectively. Subsequently, landslide susceptibility maps were divided into four classes, including low, moderate, high, and very high susceptibility. The results revealed that the RF, BRT, CART, and GLM models produced reasonable accuracy in landslide susceptibility mapping. The outcome maps would be useful for general planned development activities in the future, such as choosing new urban areas and infrastructural activities, as well as for environmental protection.     

Photocatalytic activity evaluation of TiO<Subscript>2</Subscript> nanoparticles based on COD analyses for water treatment applications: a standardization attempt

Evaluation of the photocatalytic activities of TiO₂ nanomaterials based on the chemical oxygen demand (COD) analyses under identical experimental conditions was not previously reported. In this work, COD has been selected as an adequate industrial water quality measure toward the establishment of a representative standard test method. The initial COD values of six organic pollutants representing dye, surfactants, phenols and alcohol were set at 30 ± 2 mg/L. Ten of different commercial and synthesized TiO₂ samples representing anatase, rutile and mixed phases were used and characterized. The data of photocatalytic processes were compared to that obtained using the commonly widespread Degussa-P25 TiO₂ (TD). The COD of all pollutants was completely removed by TD at UV exposure dose ≤9.36 mWh/cm². Consequently, the maximum irradiation dose was set at this value in all experiments. The percentages of COD removal as well as the values of the accumulated UV doses required for complete removal of pollutants were measured using the different TiO₂ samples. TiO₂ samples show different performance abilities toward the various pollutants compared to TD. Based on the obtained data, TiO₂ photocatalysts were divided into two categories according to the hydroxyl radical formation rates. Comparison with previous studies reveals that the photocatalytic efficiency evaluation depends on the method of measurement. COD is recommended to be used as an adequate technique of analysis that meets the purpose of water treatment applications.     

Experimental investigations on ultimate bearing capacity of peat stabilized by a group of soil–cement column: a comparative study

The aim of this paper was to determine the ultimate vertical bearing capacity of rectangular rigid footings resting on homogeneous peat stabilized by a group of cement deep mixing (CDM) columns. For this purpose, a series of physical modeling tests involving end-bearing and floating CDM columns were performed. Three length/depth ratios of 0.25, 0.5, and 0.75 and three area improvement ratios of 13.1, 19.6, and 26.2 % were considered. Bearing capacity of the footings was studied using different analytical procedures. The results indicated that compared to unimproved peat, the average ultimate bearing capacity (UBC) improvement of floating and end-bearing CDM columns were 60 and 223 %, respectively. The current study found that simple Brom’s method predicted the UBC of the peat stabilized with floating CDM columns with reasonable accuracy, but underestimated the UBC by up to 25 % in the case of end-bearing CDM columns. Published laboratory experiences of stabilizing soft soils using soil–cement columns were also collated in this paper.