Single-station ellipticity retrieval and its joint inversion with dispersion curve,for a borehole test site

To obtain the shear wave velocity profile for engineering application to near-subsurface, many geophysical techniques are used. The dispersion curve alone is unable to provide deeper shear wave velocity information for deep soil deposit; therefore, a joint inversion of dispersion curves with the horizontal over vertical (H/V) (i.e., apparently ellipticity) curve is recommended. The H/V curve obtained from the microtremor recording contains a major part of Love wave contribution to the noise wavefield horizontal component. Due to this presence of Love wave fraction, the H/V curve does not completely replicate the ellipticity of Rayleigh wave. In this study, we try to compare the Rayleigh wave ellipticity obtained from the borehole velocity model to the H/V curve obtained at the same locality from seismic ambient noise recording. Two different techniques available for the Love effect minimization are tested and compared with the borehole ellipticity. Finally, the joint inversion of H/V and dispersion curve is made, which shows great correspondence with the previous measurement at the site.     

Impacts of future land cover and climate change on the water balance in northern Iran

We evaluated the potential impacts of future land cover change and climate variability on hydrological processes in the Neka River basin, northern Iran. This catchment is the main source of water for the intensively cultivated area of Neka County. Hydrological simulations were conducted using the Soil and Water Assessment Tool. An ensemble of 17 CMIP5 climate models was applied to assess changes in temperature and precipitation under the moderate and high emissions scenarios. To generate the business-as-usual scenario map for year 2050 we used the Land Change Modeler. With a combined change in land cover and climate, discharge is expected to decline in all seasons except the end of autumn and winter, based on the inter-model average and various climate models, which illustrated a high degree of uncertainty in discharge projections. Land cover change had a minor influence on discharge relative to that resulting from climate change.     

Geophysical investigation of the Colônia structure,Brazil

The origin of the nearly circular Colônia structure, located at the southwestern edge of the city of São Paulo, Brazil, has been the subject of a long‐standing debate, ever since the 1960s when the structure was first investigated by geophysical methods. The structure still raises interest for geological research, as its sedimentary infill holds important paleoclimatic information about the evolution of the tropical rainforest, as well as the interplay between the South American summer monsoon, the Intertropical Convergence Zone, and the southern Westerly wind belt—for possibly as long as several million years. In addition, the search for evidence to conclusively establish the origin of this structure continues, and the answer most likely lies in the lower portions of the basin's sedimentary infill, which also holds a significant potential for underground water resources. Here, we present the results from recent seismic (reflection and HVSR), gravimetric, and geoelectrical surveys. They have provided a reliable image of the sedimentary infill, and the maximum depth to basement within the structure has been constrained consistently by the different methods to approximately ?400 m. The geophysical data have also allowed to map the lateral contact between the crystalline basement rocks and the sedimentary infill, which indicates a diameter of approximately 2.8 km for the sedimentary basin, with 3.6 km being the diameter of the outermost limit of the structure. A total of six seismic stratigraphic boundaries were identified within the sedimentary infill, providing a framework for the planning of a deep drilling campaign and subsequent sampling program aimed at geological and paleoclimatology studies.     

Limit loads of ship structure components using the elastic modulus adjustment procedure (EMAP)

In this paper, the m_α-tangent method is implemented in conjunction with elastic modulus adjustment procedure (EMAP) and an algorithm has been proposed for limit load estimation. This technique is applied to a number of ship structure components possessing different kinematic redundancies. Specifying spatial variations in the elastic modulus, numerous sets of statically admissible and kinematically admissible stress and strain distributions are generated, and both lower and upper bound limit load multipliers are obtained. Utilizing the lower and upper bound multipliers, accurate limit loads of ship structure components are then determined using the m_α-tangent method. Results are compared with the inelastic finite element results and the available analytical solutions.     

Experimental study on local scour around single oblong pier fitted with a collar in a 180 degree flume bend

In this work, investigation on the development of local scour around an oblong pier in a 180 degree flume bend is presented. Scour hole can cause failure of the bridge especially during the river floods. In this study, the use of oblong collars for reducing the effects of local scour at a bridge pier is presented together with the time aspect of the scour development. Tests were conducted using one oblong pier in positions of 60degree under one flow conditions. The study was conducted using a physical hydraulic model operated under clear-water conditions in cohesionless bed material. In this study, the time development of the local scour around the oblong pier fitted with and without collar plates was studied. Investigated was the effect of size and elevation collar on the time development of scour and its efficacy at preventing scour at a bridge pier. The time development of the scour hole around the model pier with and without a collar installed was compared with similar studies on bridge piers. The results of the model study indicated that the maximum depth of scour is highly dependent on the experimental duration. It was observed that, as the minimum depth of scour occurs for the square collar at width of 3B placed at elevation of 0.1B below the bed and the size of a collar plate increases, the scour decreases. Measuring depth of scouring based on experimental observation, an empirical relation is developed with regression coefficient 95%.     

Late Quaternary tectono-geomorphological investigations of Zanskar Basin,NW Himalaya,India, using geospatial techniques

Geospatial techniques play a crucial role in geomorphic studies, particularly in the challenging terrains like mountainous regions, inaccessible areas and densely vegetated landscapes, where geomorphic features cannot be recorded easily. Tectono-geomorphologic observations provide important clues regarding the landscape evolution, morpho-dynamics and ongoing tectonism of the region. The present study has been carried out in the Zanskar Basin (ZB), located to the south of the Indus Tsangpo Suture Zone (ITSZ), in the hinterland of the NW Himalaya. This study has been carried out to assess and evaluate active tectonics by employing tectono-geomorphic analysis, dynamics in drainage networks, geomorphological field observations and the Geographic Information System (GIS) environment. High-resolution satellite images, topographic maps and the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) were used to generate primary data sets, which were corroborated with field investigations for valid inferences. The geometry of the ZB suggests that continuous tectonic activity exerts first-order control on the overall shape, size and structure of the ZB. This first-order response is clearly reflected in the landforms modified by tectonic processes, namely, linear mountain fronts, elongated shape and tilting of the basin, braided and meandering river courses and lower stream length gradient index values in hard rock terrain. The ZB exhibits several eye-catching geomorphic features, such as well-defined triangular facets with wide base lengths and wine-glass valleys with small outlets along the footwall block of the Zanskar Shear Zone/South Tibetan Detachment System (ZSZ/STDS), as well as the presence of wind gaps, water gaps, bedrock incision, incised and entrenched valleys, narrow gorges and a high incision rate inferring active tectonics and recent uplift in the region. In addition, the existence of uplifted river terraces, as well as the stepped morphology of fans and strath terraces, suggests that the region is experiencing recent activity and ongoing tectonic uplift. These modified geomorphic characteristics suggest that the hinterland, which is part of the NW Himalaya, is tectonically quite active and has experienced a differential rate of tectonics during its evolution. The quantified geomorphic indices and their relations with the tectonics, climate and erosion activity infer that the basin geometry is mostly controlled by the ZSZ/STDS that dips 20°–70° NE, the south-dipping Zanskar Counter Thrust (ZCT) and other local tectonic elements like the Choksti Thrust (CT), Stondgey Thrust, Zangla Thrust and tectonic structures. The synergised results of quantified geomorphic indices and tectono-geomorphic evidence in the ZB strongly indicate that both the past and ongoing tectonism have significantly shaped and modified geomorphology of the ZB.     

Depositional history of a muddy sabkha complex in the Sokoto Basin of Nigeria,West Africa

Sedimentological and stratigraphical analysis of the Sokoto Basin has resulted in recognition of four lithostratigraphic units. They are Unit A—siltstone and fine-grained sandstone; Unit B—shale and marl; Unit C—limestone and calcareous shale; and Unit D—red sandstone. Unit A represents a wadi plain system composed of desert-alluvial beds; Unit B, a mud-rich sabkha system; and Unit C, an inner-shelf carbonate system. A marine transgression from the northwest began in the Maastrichtian and reached its peak in the Palaeocene. After regression in the late Palaeocene, the area was subjected to erosion, followed by fluvial sedimentation of Unit D. Wadi plain beds and mud-rich sabkha facies of Sokoto Basin are similar to alluvial and coastal mud-flat deposits in the northwestern Gulf of California and ephemeral stream and tidal-flat sediments in Gladstone Embayment, Australia.