Aftershock probabilistic seismic hazard analysis for Bushehr province in Iran using ETAS model

Natural Hazards - Aftershock probabilistic seismic hazard analysis (APSHA) has a key role in risk management after a major earthquake. The main goal of the current study is to assess aftershock...     

Characterization of the Lebanese Jurassic–Cretaceous carbonate stratigraphic sequence: a geochemical approach

The Lebanese crustal segment is part of a much larger carbonate platform deposited along the northwestern margin of the Arabian Plate, in the eastern Mediterranean region. It is made up mainly of Jurassic–Cretaceous carbonate rocks. Most of this stratigraphic sequence is exposed in the Nahr Ibrahim canyon and surrounding areas in central Lebanon. The various formations, from the oldest unit (the Lower Jurassic Kesrouane Formation) to the Upper Cretaceous Chekka Formation, are made up of different types of carbonate rocks including micritic limestone, medium‐ to coarse‐grained dolostone, biomicritic (chalk), biosparrudite limestone, micritic dolostone, pelmicrite, marl and marly limestone. Results of this first chemical investigation on the Lebanese carbonate platform show that the micritic limestone of the Kesrouane Formation is relatively enriched in Ca, Na and Sc, and has low rare‐earth element (REE) contents. The marl units of the Hammana Formation are enriched in Al, Fe, K, Ti, Rb, Ga, Nb, U, Th and REE. The chalk of the Chekka Formation shows the highest phosphorus content. A significant increase in P and Sr contents with time (from the Lower Jurassic to the Upper Cretaceous carbonate units) characterizes the Lebanese sequence; this is interpreted to be related to a possible increase in continental weathering rates during the Mesozoic. Enrichment in Ni, Ti and Nb in some formations is interpreted to be linked to Mesozoic volcanism in central Lebanon. The Cretaceous formations are subdivided according to their REE patterns into two distinct groups: limestones (Mdairej, Sannine and Maameltain formations) which are depleted in REE; and marl/chalk (Hammana and Chekka formations) which are significantly enriched in REE. On several geochemical variation diagrams, such as the K–Ti–P triangular plot, the Lebanese Mesozoic carbonate formations are found to occupy distinct compositional fields. Thus, carbonate geochemistry could prove to be a powerful tool (especially when combined with petrographic data) in characterizing and correlating carbonate formations (chemical stratigraphy), particularly in regions where field evidence may be limited. Results of this study have significant implications for the entire carbonate platform that covers a large part of the eastern Mediterranean region. Copyright © 2002 John Wiley & Sons, Ltd.     

Recognition of shallow karst water resources and cave potentials using thermal infrared image and terrain characteristics in semi-arid regions of Iran

Shallow karst water resources and caves may influence land surface temperatures due to cold transfer property of rocks and evaporation from buried karst. The objective of this research was to develop a method for recognition of karst areas based on evaluating the surface characteristics that manifest itself by low land surface temperature in the satellite images. Investigation of thermal ETM⁺ image of the study region in Iran showed that parts of carbonate rocks that bear karst water are relatively cooler compared to areas with similar terrain conditions. Relational modeling provided useful information on spatial distribution of areas that have the potential to hold karst water resources and/or caves. Further inspection of ASTER images, along with geotechnical, geophysical and geological field surveys verified the approach. Significant correlation was found between electrical resistivity and thermal band values. The method may be used as a primary exploratory tool for shallow karst water explorations in similar areas.     

Parameterizing canopy resistance using mechanistic and semi‐empirical estimates of hourly evapotranspiration: critical evaluation for irrigated crops in the Mediterranean

In this paper two models are presented for calculating the hourly evapotranspiration λE (W m^?2) using the Penman–Monteith equation. These models were tested on four irrigated crops (grass, soya bean, sweet sorghum and vineyard), with heights between 0·1 and 2·2 m at the adult growth stage. In the first model (Katerji N, Perrier A. 1983. Modélisation de l'évapotranspiration réelle ETR d'une parcelle de luzerne : rôle d'un coefficient cultural. Agronomie 3(6): 513–521, KP model), the canopy resistance r_c is parameterized by a semi‐empirical approach. In the second model (Todorovic M. 1999. Single‐layer evapotranspiration model with variable canopy resistance. Journal of Irrigation and Drainage Engineering—ASCE 125: 235–245, TD model), the resistance r_c is parameterized by a mechanistic model. These two approaches are critically analysed with respect to the underlying hypotheses and the limitations of their practical application. In the case of the KP model, the mean slope between measured and calculated values of λE was 1·01 ± 0·6 and the relative correlation coefficients r² ranged between 0·8 and 0·93. The observed differences in slopes, between 0·96 and 1·07, were not associated with the crop height. This model seemed to be applicable to all the crops examined. In the case of the TD model, the observed slope between measured and calculated values of λE for the grass canopy was 0·79. For the other crops, it varied between 1·24 and 1·34. In all the situations examined, the values of r² ranged between 0·73 and 0·92. The TD model underestimated λE in the case of grass and overestimated it in the cases of the other three crops. The under‐ or overestimation of λE in the TD model were due: (i) to some inaccuracies in the theory of this model, (ii) to not taking into account the effect of aerodynamic resistance r_a in the canopy resistance modelling. Therefore, the values of r_c were under‐ or overestimated in consequence of mismatching the crop height. The high value of air vapour pressure deficit also contributed to the overestimation of λE, mainly for the tallest crop. The results clarify aspects of the scientific controversy in the literature about the mechanistic and semi‐empirical approaches for estimating λE. From the practical point of view the results also present ways for identifying the most appropriate approach for the experimental situations encountered. Copyright © 2010 John Wiley & Sons, Ltd.     

Impacts of climate change on soil moisture and evapotranspiration in reconstructed watersheds in northern Alberta,Canada

This study aims at developing a generalized understanding of the sensitivity of soil moisture patterns in reconstructed watersheds, in northern Alberta, to changes in the projected precipitation in the twenty‐first century. The GSDW model is applied to three watersheds using climate scenarios generated using daily precipitation and air temperature output from a global climate model (CGCM3), under A2 and B1 emission scenarios, to simulate the corresponding soil moisture. CGCM3 results indicate an increase in the mean annual temperature for Fort McMurray, Alberta of 3·3 (A2) and 2·4 °C (B1), and an increase in the predicted annual precipitation of 34% (A2) and 8·6% with A2 and B1 emission scenarios, respectively. The GSDW model is used, along with onsite historical data, to downscale A2 and B1 emission scenarios and to evaluate the future hydrological performance of the designated watersheds with respect to soil moisture deficit and actual evapotranspiration using a probabilistic framework. The forecasted maximum soil moisture deficit values based on A2 and B1 emission scenarios are expected to decrease compared to those based on the current, largely because of the expected increase in precipitation rates, associated with an expected increase in evapotranspiration. Copyright © 2011 John Wiley & Sons, Ltd.     

Modeling Fate and Transport of Volatile Organic Compounds (VOCs) Inside Sewer Systems

Hazardous waste site investigations have shown that volatile organic compounds (VOCs) can be transported via sewer pipes and migrate into indoor spaces. Despite field data confirming the presence of this exposure pathway, there is lack of context-based numerical models that provide guidance to characterize and predict VOCs concentration in sewer gas at vapor intrusion sites. Particularly, this poses a challenge when assessing and mitigating risks associated with these exposure pathways. Therefore, a numerical model has been developed to simulate the concentration of VOCs in sewer gas in different stages throughout the sewer lines. The developed model considers various input parameters, including temperature, sewer liquid depth, groundwater depth, and sewer construction characteristics to incorporate local and operational conditions. The model's output is verified using field data from a sewer system constructed near a Superfund site. Moreover, a sensitivity analysis was conducted to evaluate the model's response to variation of the external input parameters. To the best of our knowledge, this study is the first attempt to model VOCs concentration in sewer gas, particularly to address vapor intrusion. The developed model can be used as a numerical tool to support the development of sewer assessment guidelines, risk assessment studies, and mitigation strategies.     

Assessment and Modification of Sherard Chemical Method for Evaluation of Dispersion Potential of Soils

Soil dispersion is a phenomenon in which soil particles become afloat when they are exposed to water, and are carried away by the force of seepage. In spite of that soil dispersion is due to its chemical composition, the results obtained from the chemical methods, especially from the most widely used, Sherard method does not match with the results of well-known Pinhole test. This study tries to evaluate and modify the Sherard diagram for determination of dispersion potential of clayey soils. For this purpose, several natural soil samples were collected from different regions of Iran and some artificial soil samples were made by adding different percentages of four chemical agents, including sodium chloride, sodium carbonate, sodium sulfate, and sodium polyphosphate to a natural soil. The physical, chemical and index properties of all samples were determined and for determination of dispersion potential, the commonly used chemical test (Sherard method) and Pinhole test were employed. The results obtained from the tests showed that the Sherard chemical method which is solely based on the amount and type of the existing cations, is not able to determine soil dispersion correctly since the role of some anions, especially chloride is neglected. It was also found that among the existing anions in the soil, the chloride on the contrary to sodium acts as a flocculating factor. The results showed that by converting the vertical axis of the Sherard chart from sodium% to (sodium chloride)%, its conformity to the results of Pinhole tests increases considerably.     

GJ 581 update: Additional evidence for a Super‐Earth in the habitable zone

We present an analysis of the significantly expanded HARPS 2011 radial velocity data set for GJ 581 that was presented by Forveille et al. (2011). Our analysis reaches substantially different conclusions regarding the evidence for a Super‐Earth‐mass planet in the star's Habitable Zone. We were able to reproduce their reported χ²_ν and RMS values only after removing some outliers from their models and refitting the trimmed down RV set. A suite of 4000 N‐body simulations of their Keplerian model all resulted in unstable systems and revealed that their reported 3.6σ detection of e = 0.32 for the eccentricity of GJ 581e is manifestly incompatible with the system's dynamical stability. Furthermore, their Keplerian model, when integrated only over the time baseline of the observations, significantly increases the χ²_ν and demonstrates the need for including non‐Keplerian orbital precession when modeling this system. We find that a four‐planet model with all of the planets on circular or nearly circular orbits provides both an excellent self‐consistent fit to their RV data and also results in a very stable configuration. The periodogram of the residuals to a 4‐planet all‐circular‐orbit model reveals significant peaks that suggest one or more additional planets in this system. We conclude that the present 240‐point HARPS data set, when analyzed in its entirety, and modeled with fully self‐consistent stable orbits, by and of itself does offer significant support for a fifth signal in the data with a period near 32 days. This signal has a false alarm probability of <4% and is consistent with a planet of minimum mass 2.2 M_⊕, orbiting squarely in the star's habitable zone at 0.13 AU, where liquid water on planetary surfaces is a distinct possibility (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)