Thermal springs,fumaroles and gas vents of continental Yemen: Their relation with active tectonics,regional hydrology and the country’s geothermal potential

Most thermal springs of continental Yemen (about 65 emergences at 48 sampling sites) and a couple of fumaroles and boiling water pools have been sampled and analyzed for chemical and isotopic composition in the liquid phase and the associated free-gas phase. Whatever the emergence, all the water discharges have an isotopic signature of meteoric origin. Springs seeping out from high altitudes in the central volcanic plateau show a prevalent Na–HCO₃-composition, clearly affected by an anomalous flux of deep CO₂ deriving from active hydrothermal systems located in the Jurassic Amran Group limestone sequence and/or the Cretaceous Tawilah Group, likely underlying the 2000–3000 m thick volcanic suite. At lower elevations, CO₂ also affects the composition of some springs emerging at the borders of the central volcanic plateau.     

Development of stochastic dynamic Nash game model for reservoir operation II. The value of players’ information availability and cooperative behaviors

Stochastic dynamic game models can be applied to derive optimal reservoir operation policies by considering interactions among water users and reservoir operator, their preferences, their levels of information availability and cooperative behaviors. The stochastic dynamic game model with perfect information (PSDNG) has been developed by [Ganji A, Khalili D, Karamouz M. Development of stochastic dynamic Nash game model for reservoir operation. I. The symmetric stochastic model with perfect information. Adv Water Resour, this issue]. This paper develops four additional versions of stochastic dynamic game model of water users interactions based on the cooperative behavior and hydrologic information availability of beneficiary sectors of reservoir systems. It is shown that the proposed models are quite capable of providing appropriate reservoir operating policies when compared with alternative operating models, as indicated by several reservoir performance characteristics. Among the proposed models, the selected model by considering cooperative behavior and additional hydrologic information (about the randomness nature of reservoir operation parameters), as exercised by reservoir operator, provides the highest attained level of performance and efficiency. Furthermore, the selected model is more realistic since it also considers actual behavior of water users and reservoir operator in the analysis.     

Harmonic wave diffraction by two circular cavities in a poroelastic formation

This study investigates the dynamic interaction of time harmonic plane waves with a pair of parallel circular cylindrical cavities of infinite length buried in a boundless porous elastic fluid-saturated medium. The novel features of Biot dynamic theory of poroelasticity along with the appropriate wave field expansions, the pertinent boundary conditions, and the translational addition theorems for cylindrical wave functions are employed to develop a closed-form solution in the form of infinite series. The analytical results are illustrated with numerical examples in which two empty cavities are insonified by a fast compressional or a shear wave at end-on incidence. The basic dynamic field quantities such as the hoop stress amplitude and the radial displacement of the elastic frame are evaluated and discussed for representative values of the parameters characterizing the system. The effects of the proximity of the two cavities, the incident wave frequency and type are examined. Particular attention has been focused on multiple scattering interactions in addition to the slow wave coupling effects which is known to be the primary distinction of the scattering phenomenon in poroelasticity from the classical elastic case. Limiting case involving two empty cylindrical cavities in an elastic solid is considered and excellent agreement with a well-known solution is established.     

Dinoflagellate and foraminiferal biostratigraphy of the Gurpi Formation (upper Santonian–upper Maastrichtian), Zagros Mountains, Iran

A rich dinoflagellate cyst assemblage has been recovered from an outcrop of the Gurpi Formation, the hydrocarbon source rock in the South Iranian Basin. Key dinoflagellates recorded in the section studied provide a means of correlation with zonation schemes for Australasia and north-west Europe. These include Eucladinium kaikourense, Nelsoniella aceras, Odontochitina spp., Cannosphaeropsis utinensis, Palaeocystodinium denticulatum and Dinogymnium spp. The assemblage points to a late Santonian–late Maastrichtian age for the Gurpi Formation. Dinoflagellate and planktonic foraminiferal evidence indicates the presence of a hiatus spanning the uppermost Maastrichtian to at least the lowermost Danian at the base of a glaucony-rich layer separating the Gurpi Formation from the overlying Pabdeh Formation. Palynofacies and lithofacies profiles suggest that the sediments were deposited in an open, relatively deep marine outer ramp environment belonging to ramp facies 8 and 9.     

Drainage evolution in response to fold growth in the hanging-wall of the Khazar fault, north-eastern Alborz, Iran

The Khazar fault is an active thrust fault in the northern part of the Alborz Range, which is associated with folding (the Khazar anticline) in its hanging‐wall. Regional geological studies indicate activity of the fault in Cenozoic time, and active propagation of the fault‐related folding towards the west. The Neka river drainage basin, which is a longitudinal river flowing mostly in the backlimb of the Khazar anticline, shows evidence for active folding and faulting influencing drainage evolution. Observations are made in different parts of the Neka river course, according to which a new morphotectonic feature is introduced within the river basin, termed as ‘tilted reach’. This feature is considered as a result of river course tilting in the backlimb of the growing fold, diversion, and capture of the river by other rivers. Consecutive episodes of similar events would have resulted in the development of a long drainage basin parallel to the growing fold structure.     

Axisymmetric interaction of a rigid disc with a transversely isotropic half‐space

A theoretical formulation is presented for the determination of the interaction of a vertically loaded disc embedded in a transversely isotropic half‐space. By means of a complete representation using a displacement potential, it is shown that the governing equations of motion for this class of problems can be uncoupled into a fourth‐order partial differential equation. With the aid of Hankel transforms, a relaxed treatment of the mixed‐boundary value problem is formulated as dual integral equations, which, in turn, are reduced to a Fredholm equation of the second kind. In addition to furnishing a unified view of existing solutions for zero and infinite embedments, the present treatment reveals a severe boundary‐layer phenomenon, which is apt to be of interest to this class of problems in general. The present solutions are analytically in exact agreement with the existing solutions for a half‐space with isotropic material properties. To confirm the accuracy of the numerical evaluation of the integrals involved, numerical results are included for cases of different degrees of the material anisotropy and compared with existing solutions. Further numerical examples are also presented to elucidate the influence of the degree of the material anisotropy on the response. Copyright © 2009 John Wiley & Sons, Ltd.     

Stage–discharge estimation in straight compound channels using isovel contours

For various hydrological applications such as flood control projects, a knowledge of stage–discharge relationship is of particular interest to river engineers. Stage–discharge curves in compound channels cannot be easily predicted in comparison with single channels due to their 3D characteristics of flow. In this paper, the concept of cross‐sectional isovel contours is used for estimation of stage–discharge curves in compound channels. The multivariate Newton's method is applied to the difference between the observed and estimated data to optimize the exponent values of the governing parameters. The accuracy of the proposed model is tested successfully against available experimental results, which are taken from the Flood Channel Facility (FCF) laboratory. Then the results are compared with the Single and Divided Channel Methods (SCM and DCM, respectively), the Weighted Divided Channel Method (WDCM), the exchange discharge method (EDM), and the Coherence Method (COHM). The average values of mean absolute percentage error (MAPE) and normalized root mean square error (NRMSE) in discharge estimation based on each referenced section at any level for 6 sections of the experimental cases are within 3.1% and 0.023, respectively. The biggest advantage of the proposed method is its inherent simplicity, which does not need any calibration.     

Numerical modeling of strongly coupled microscale multiphase flow and solid deformation

When fluid flows in porous media under subsurface conditions, significant deformation can occur. Such deformation is dependent on structural and phase characteristics. In this paper, we investigate the effect of multiphase flow on the deformation of porous media at the pore scale by implementing a strongly coupled partitioned solver discretized with finite volume (FV) technique. Specifically, the role of capillary forces on grain deformation in porous media is investigated. The fluid and solid subdomains are meshed using unstructured independent grids. The model is applied for solving multiphase coupled equations and is capable of capturing pore scale physics during primary drainage by solving the Navier-Stokes equation and advecting fluid indicator function using volume of fluid (VOF) while the fluid is interacting with a nonlinear elastic solid matrix. The convergence of the coupled solver is accelerated by Aitken underrelaxation. We also reproduce geomechanical stress conditions, at the pore scale, by applying uniaxial stress on the solid while simultaneously solving the multiphase fluid-solid interaction problem to investigate the effect of external stress on fluid occupancy, velocity-field distribution, and relative permeability. We observe that the solid matrix exhibits elasto-capillary behavior during the drainage sequence. Relative permeability endpoints are shifted on the basis of the external stress exerted.