Plio-Quaternary stress states in NE Iran: Kopeh Dagh and Allah Dagh-Binalud mountain ranges

NE Iran, including the Kopeh Dagh and Allah Dagh-Binalud deformation domains, comprises the northeastern boundary of the Arabia–Eurasia collision zone. This study focuses on the evolution of the Plio-Quaternary tectonic regimes of northeast Iran. We present evidence for drastic temporal changes in the stress state by inversion of both geologically and seismically determined fault slip vectors. The inversions of fault kinematics data reveal distinct temporal changes in states of stress during the Plio-Quaternary (since ～ 5 Ma). The paleostress state is characterized by a regional transpressional tectonic regime with a mean N140 ± 10°E trending horizontal maximum stress axis (σ₁). The youngest (modern) state of stress shows two distinct strike-slip and compressional tectonic regimes with a regional mean of N030 ± 15°E trending horizontal σ₁. The change from the paleostress to modern stress states has occurred through an intermediate stress field characterized by a mean regional N trending σ₁. The inversion analysis of earthquake focal mechanisms reveals a homogeneous, transpressional tectonic regime with a regional N023 ± 5°E trending σ₁. The modern stress state, deduced from the youngest fault kinematics data, is in close agreement with the present-day stress state given by the inversions of earthquake focal mechanisms. According to our data and the deduced results, in northeast Iran, the Arabia–Eurasia convergence is taken up by strike-slip faulting along NE trending left-lateral and NNW trending right-lateral faults, as well as reverse to oblique-slip reverse faulting along NW trending faults. Such a structural assemblage is involved in a mechanically compatible and homogeneous modern stress field. This implies that no strain and/or stress partitioning or systematic block rotations have occurred in the Kopeh Dagh and Allah Dagh-Binalud deformation domains. The Plio-Quaternary stress changes documented in this paper call into question the extrapolation of the present-day seismic and GPS-derived deformation rates over geological time intervals encompassing tens of millions of years.     

Vertically self-gravitating ADAFs in the presence of toroidal magnetic field

Force due to the self-gravity of the disc in the vertical direction is considered to study its possible effects on the structure of a magnetized advection-dominated accretion disc. We present steady-sate self similar solutions for the dynamical structure of such a type of the accretion flows. Our solutions imply reduced thickness of the disc because of the self-gravity. It also imply that the thickness of the disc will increase by adding the magnetic field strength.     

Aftershocks study of the 2006 Silakhur earthquake (Zagros, Iran): seismological evidences for a pull-apart basin along the Main Recent Fault, Doroud segments

The Doroud segment of the Main Recent Fault (“MRF”) is studied by installing a local seismic network of 35 short-period stations for a period of 13 weeks from 21 June 2007 to 19 September 2007 in the Silakhur region of the Zagros continental collision zone, close to the epicenter of the 31 March 2006 Silakhur earthquake (M _w  ∼ 6.1). Our seismic network also covers the Qale-Hatam and Vanaei segments of the MRF and part of the Nahavand fault. We investigate the geometry and mechanism of the causative fault(s) of the 2006 Silakhur earthquake using aftershocks recorded by the dense local network. Most of the aftershocks in this region are located at a depth of 4–11 km, shallower depth than usual for other seismic zones in the Zagros. The distribution of the aftershocks along the course of the river indicates that older faults in the Silakhur region have been activated during the 2006 earthquake and only a few aftershocks have occurred on the Doroud fault. Tensional and compressional components in the northern part of the Doroud fault are interpreted as a pull-apart basin which has been activated by the right-lateral strike-slip movement of the Doroud fault.     

Developing a novel methodology for ecological risk assessment of thiosalts

A new methodology is developed to estimate an aquatic community toxicity threshold concentration based on the limited toxicity data that are available for thiosalts. To analyze the indirect effect of thiosalts on decreasing pH, an exposure model is developed that estimates the residual concentration of thiosalts and pH in the water body. The results from this model are incorporated in thiosalts risk assessment and a case study is used to illustrate the applicability of the proposed model. In this study, the exposure model predicts that, trithionate and tetrathionate degraded to $ {{\text{SO}}_{4}}^{2 - } $ ions, $ {{\text{HSO}}_{3}}^{ - } $ ions, $ {{\text{SO}}_{3}}^{2 - } $ ions and elemental sulfur. The concentration of thiosulfate, trithionate and tetrathionate, initially at 25, 40 and 6 mg/L, respectively are expected to decrease. Over the duration of 77 h, thiosulfate degrades completely, while the estimated residual trithionate and tetrathionate concentrations are 13 and 5.77 mg/L, respectively. pH of the undiluted effluent is estimated to decrease from 9.2 to 5.6 within an hour of the effluent discharge and decreases further to 4 over a period of next 3 days. A framework and methodology developed in this paper can be utilized to estimate the potential direct and indirect risk of thiosalts exposure to ecological entities.     

Radiation spectrum of a magnetized supercritical accretion disc with thermal conduction

we examine the effect of thermal conduction on the observational properties of a super critical hot magnetized flow. We obtained self-similar solution of a magnetized disc when the thermal conduction plays an important role. Follow of our first paper (Ghasemnezhad et al. in Astrophys. J. 750, 2012 (hereafter GKA12)) we have extended our solution on the observational appearance of the disc to show how physical condition such as thermal conduction, viscosity, and advection will change the observed luminosity of the disc, Continuous spectra and surface temperature of such discs was plotted. We apply the present model to black-hole X-ray binary LMC X-3 and narrow-line seyfert 1 galaxies, which are supposed to be under critical accretion rate. Our results show clearly that the surface temperature is strongly depends on the thermal conduction, the magnetic field and advection parameter. However we see that thermal conduction acts to oppose the temperature gradient as we expect and observed luminosity of the disc will reduce when thermal conduction is high. We have shown that in this model the spectra of critical accretion flows strongly depends on the inclination angle.     

Viscous-resistive ADAF with a general large-scale magnetic field

We have studied the structure of hot accretion flow bathed in a general large-scale magnetic field. We have considered magnetic parameters , where are the Alfvén sound speeds in three direction of cylindrical coordinate (r,φ,z). The dominant mechanism of energy dissipation is assumed to be the magnetic diffusivity due to turbulence and viscosity in the accretion flow. Also, we adopt a more realistic model for kinematic viscosity (ν=αc _s H), with both c _s and H as a function of magnetic field. As a result in our model, the kinematic viscosity and magnetic diffusivity (η=η ₀ c _s H) are not constant. In order to solve the integrated equations that govern the behavior of the accretion flow, a self-similar method is used. It is found that the existence of magnetic resistivity will increase the radial infall velocity as well as sound speed and vertical thickness of the disk. However the rotational velocity of the disk decreases by the increase of magnetic resistivity. Moreover, we study the effect of three components of global magnetic field on the structure of the disk. We found out that the radial velocity and sound speed are Sub-Keplerian for all values of magnetic field parameters, but the rotational velocity can be Super-Keplerian by the increase of toroidal magnetic field. Also, Our numerical results show that all components of magnetic field can be important and have a considerable effect on velocities and vertical thickness of the disk.