Calibration of the specific barrier model to Iranian plateau earthquakes and development of physically based attenuation relationships for Iran

Earthquake ground-motion relationships for soil and rock sites in Iran have been developed based on the specific barrier model (SBM) used within the context of the stochastic modeling and calibrated against up-to-date Iranian strong-motion data. A total of 171 strong-motion accelerograms recorded at distances of up to 200 km from 24 earthquakes with moment magnitudes ranging from Mw 5.2 to 7.4 are used to determine the region-specific source parameters of this model. Regression analysis was conducted using the “random effects” methodology that considers both earthquake-to-earthquake (inter-event) variability and within-earthquake (intra-event) variability to effectively handle the problem of weighting observations from different earthquakes. The minimization of the error function in each iteration of the “random effects” procedure was performed using the genetic algorithm method. The residuals are examined against available Iranian strong-motion data to confirm that the model predictions are unbiased and that there are no significant residual trends with distance and magnitude. No evidence of self-similarity breakdown is observed between the source radius and its seismic moment. To verify the robustness of the results, tests were performed to confirm that the results are unchanged if the number of observations is changed by removing different randomly selected datasets from the original database. Stochastic simulations, using the derived SBM, are then performed to predict peak ground-motion and response spectra parameters for a wide range of magnitudes and distances. The stochastic SBM predictions agree well with the new empirical regression equations proposed for Iran, Europe and Middle East in the magnitude–distance ranges well represented by the data. It has been shown that the SBM of this study provides unbiased ground-motion estimates over the entire frequency range of most engineering interests (1–10 Hz) for the Iranian earthquakes. Our results are also important for the assessment of hazards in other seismically active environments in the Middle East and Mediterranean regions.     

Competing impact of anthropogenic emissions and meteorology on the distribution of trace gases over Indian region

The spatial distribution of trace gases exhibit large spatial heterogeneity over the Indian region with an elevated pollution loading over densely populated Gangetic Plains (IGP). The contending role and importance of anthropogenic emissions and meteorology in deciding the trace gases level and distribution over Indian region, however, is poorly investigated. In this paper, we use an online regional chemistry transport model (WRF/Chem) to simulate the spatial distribution of trace gases over Indian region during one representative month of only three meteorological seasons namely winter, spring/summer and monsoon. The base simulation, using anthropogenic emissions from SEAC⁴RS inventory, is used to simulate the general meteorological conditions and the realistic spatial distribution of trace gases. A sensitivity simulation is conducted after removing the spatial heterogeneity in the anthropogenic emissions, i.e., with spatially uniform emissions to decouple the role of anthropogenic emissions and meteorology and their role in controlling the distribution of trace gases over India. The concentration levels of Ozone, CO, SO₂ and NO₂ were found to be lower over IGP when the emissions are uniform over India. A comparison of the base run with the sensitivity run highlights that meteorology plays a dominant role in controlling the spatial distribution of relatively longer-lived species like CO and secondary species like Ozone while short-lived species like NO_X and SO₂ are predominantly controlled by the spatial variability in anthropogenic emissions over the Indian region.     

Development and verification of the comprehensive model for physical properties of hydrate sediment

Natural gas hydrate is widely distributed all over the world and may be a potential resource in the near future, whereas hydrate dissociation during the development affects wellbore stability and drilling safety. However, the present modeling of hydrate reservoir parameters ignored the influence of effective stress and only considered the hydrate saturation. In this paper, a series of stress sensitivity experiments for the unconsolidated sandstone were carried out, and the influence of mean effective stress on physical parameters was obtained; a comprehensive model for the physical parameters of hydrate reservoir was developed subsequently. With the help of ABAQUS finite element software, the established comprehensive model was verified by the use of the wellbore stability numerical model of hydrate reservoir. The verification results show that ignoring the effect of mean effective stress on the parameters of hydrate formation aggravates the invasion of drilling fluid into the hydrate formation. Besides, ignoring the stress sensitivity of reservoir physical parameters will underestimate the wellbore instability during hydrate drilling, which will be a threat to the safety of gas hydrate drilling. At the end of the drilling operation, the maximum plastic strain of the model for considering and not considering stress sensitivity was 0.0145 and 0.0138, respectively. Therefore, the established comprehensive model will provide a theoretical support for accurately predicting the engineering geological disasters in hydrate development process.     

Hydrochemistry and Classification of Groundwater Resources of Ishwardi Municipal Area,Pabna District,Bangladesh

The chemical property of groundwater depends largely on the mineralogical composition of the rocks through which the water has moved and the rate of movement and these characteristics of surface water depend on organic and inorganic reactions, industrial effluents, rainfall and temperature etc. The underground water tends to contain more dissolved materials than those in surface water because of their more intimate and longer contact with organic materials of soil and rock particles. The groundwater of the studied area is dominant of alkaline earth’s (Ca²⁺ and Mg²⁺) and weak acids (HCO₃ ⁻) which may be classified as Magnesium-Bicarbonate and Calcium Carbonate types. Genetically, the groundwater of the area belongs to both “Normal Chloride” “Normal Sulphate” and “Normal Carbonate” to “Super Carbonate” group. Based on EC, SAR and RC, the groundwater of the area varies from good–excellent quality for irrigation purposes with low alkali hazard and medium salinity hazard.     

Spatial evaluation of impacts of increase in impervious surface area on SCS-CN and runoff in Nagpur urban watersheds,India

The changing land use due to rapid urbanization has profound impact on the runoff in urban watersheds. The spatial analysis in urban watersheds is felt necessary for management of surface and subsurface water regimes. Significant increase in impervious zones was observed in Nagpur urban watersheds between 2000 and 2012 having impacts on runoff, and even flash floods were observed. This study presents spatial and temporal impacts of change in urban built-up area on curve number (CN) and runoff during the years 2000 and 2012. The study also analyzes effect of slope on CN values and shows that CN increases with slope. High-resolution satellite images were used to map impervious surface areas (ISAs) which show an increase of 0.9 to 34 % during 2000–2012. Spearman’s and Pearson’s coefficients have been generated to establish relationship between runoff, impervious surface areas, vegetation index, slope, and runoff coefficient. It has been hypothetically assumed that if 100, 50, and 25 % rooftop rainwater harvesting is considered, the estimated runoff reduces in 2012 as compared to the year 2000. The study suggests that increase in impervious areas within urban watersheds can be utilized for groundwater augmentation adopting rooftop rainwater-harvesting techniques and to prevent flash floods.     

Role of monsoon rain on concentrations and dispersion patterns of metal pollutants in sediments and soils of the Ganga Plain, India

 Monsoon rain causes large scale sediment-water movement and reworking of sediments of the Ganga Plain which is one of the largest fluvial systems on Earth. Geomorphology and drainage type combined with sedimentation processes play a substantial role on dispersion and transport patterns of metals bound to sediments and soils. The study area of Kanpur-Unnao industrial region in the Ganga Plain has been divided into five independent geochemical domains on the basis of sediment-geomorphic, hydrological and geochemical characters. The monsoon hydrography and physico-chemical parameters (pH, conductivity) of the river and urban drain waters play a prominent role in regulating the concentrations and behaviour of the metals in the aquatic system of the Ganga Plain. Values of pH and specific electrical conductivity of the river water of the study area decrease whereas those of the urban drain water increase in post-monsoon period. The monsoon rain reduces the contents of Co, C-org, Cr, Fe and Ni and enhances the contents of Cd, Sn and Zn in sediments of post-monsoon period. In soils, it reduces the contents of Al, Co, Fe, Mn and Ni and enhances the contents of Cd, Sn and Zn in the post-monsoon period. These changes in concentrations vary from metal to metal and from one geochemical domain to the other. An increase in the concentrations of few metals in the soils from pre- to post-monsoon periods indicates that these metals were mobilized from the overflooding of metal rich waste-water onto the fields during high water stage and also by reworking of the soils through sheet floods during the monsoon time. Despite the changes in concentrations, metal dispersion patterns in each domain remain similar both in pre- and post-monsoon periods which indicate that the geochemical and sediment-geomorphic processes operating for the metal dispersion and mobilization in sediments are persistent even after large scale sediment-water movement and reworking of the sediments during the monsoon period. Received: 4 May 1998 · Accepted: 20 October 1998     

Temperature distribution in the transition region and inner corona

The energy balance equation for a general solar atmosphere without assuming the plane-parallel approximation is solved analytically. This leads to models for both the transition region and inner corona as well as for the outer corona. The form of the latter is very similar to that of the hydrostatic conduction model of Chapman (1957). However, in this paper we confine ourselves only to the former.Model I is electron-pressure dependent but model II depends particularly on the maximum coronal temperature T _m and its corresponding altitude h _m. Both the models are compared with recently constructed temperature models of Chiuderi and Riani (1974), McWhirter et al. (1975), and Gabriel (1976a). It is concluded that our model II reproduces these models within a factor of not more than 2.     

Mathematical modelling of ionospheric TEC from Turkish permanent GNSS Network (TPGN) observables during 2009–2017 and predictability of NeQuick and Kriging models

The present study examines the ionospheric Total Electron Content (TEC) variations in the lower mid-latitude Turkish region from the Turkish permanent GNSS network (TPGN) and International GNSS Services (IGS) observations during the years 2009 to 2017. The corresponding vertical TEC (VTEC) predicted by Kriging and NeQuick-2 models are evaluated to realize their efficacy over the country. We studied the diurnal, seasonal and spatial pattern of VTEC variation and tried to estimate by a new mathematical model using the long term of 9 years VTEC data. The diurnal variation of VTEC demonstrates a normal trend with its gradual enhancement from dawn to attain a peak around 09:00–14.00 UT and reaching the minimum level after 22.00 UT. The seasonal behavior of VTEC indicates a strong semi-annual variation of VTEC with maxima in September equinox followed by March equinox and minima in June solstice followed by December solstice. Also, the spatial variation in VTEC depicts a meaningful longitudinal/latitudinal pattern altering with seasons. It decreases longitudinally from the west to the east during March equinox and June solstice increases with latitude. The comparative analysis among the GNSS-VTEC, Kriging, NeQuick and the proposed mathematical model are evaluated with the help one way ANOVA test. The analysis shows that the null hypothesis of the models during storm and quiet days are accepted and suggesting that all models are statistically significantly equivalent from each other. We believe the outcomes from this study would complement towards a relatively better understanding of the lower mid-latitude VTEC variation over the Turkish region and analogous latitudes over the globe.     

Coastal management in the Persian Gulf region within the framework of the ROPME programme of action

Persian Gulf is a semi-enclosed sea located in the Middle East and is connected to oceans through the narrow 55-km Strait of Hormuz. The Persian Gulf holds an estimated 57–66% of the world's known reserves of oil. The occurrence of three major battles in the Gulf region during the past three decades has created an atmosphere of commotion and uncertainty. Because of its marine geology, geographical location, and geopolitical sensitivity, coastal management in the Gulf region cannot be considered independently of its vast oil and natural gas reserves and environmentally related matters. The Regional Organization for Protection of Marine Environment (ROPME) forum was established in Kuwait in 1979 and quickly ratified by seven new member states (Bahrain, Iran, Iraq, Oman, Qatar, Saudi Arabia and the United Arab Emirates). Rapid growth of ROPME and shared coastal and marine environmental issues among littoral States have resulted in numerous successful plans laying the basis for future coastal management and development in the Persian Gulf region.Different plans were investigated to reach sustainable coastal management and environmental pollution prevention programmes in the Persian Gulf region and it was concluded that such plans could only be implemented when littoral states prioritize the management schemes in the Persian Gulf region and incorporate them into their own national legislation.Similar to many Regional Sea Programmes, ROPME has faced many drawbacks since its inception. Military conflicts, poor enforcement of protocols, lack of adequate coordination, disharmony among littoral states and lack of sufficient funding have put many coastal management programmes on hold.Demilitarization, enforcement of ROPME resolutions, and implementation of long-term economical growth planning are all part of an integrated coastal management programme that can bring about significant changes in the Persian Gulf area. Despite all existing differences and difficulties, many important tasks have been accomplished in the past two decades. Coastal management issues have been analyzed and well documented by ROPME. With the existing situation in the Gulf region, ROPME can effectively coordinate and implement the following tasks: monitor water quality and coastal habitat, develop and implement a comprehensive pollution prevention scheme, educate the public in terms of coastal preservation, train technical staff, put in place an effective pollution prevention and waste management programme, and establish the basis for an integrated regional coastal zone management plan.