Seismic risk assessment of a steel building supported on helical pile groups

Acta Geotechnica - Designing structures to be the least vulnerable within earthquake-prone areas is a serious challenge for structural engineers. One common and useful tool that structural...     

Wildfire impacts on schools and hospitals following the 2018 California Camp Fire

Natural Hazards - Wildfire impacts on communities have become more pronounced in recent years as the intensity and frequency of wildfires have increased in densely populated areas of the...     

An improved method for estimating life losses from dam failure in China

Stochastic Environmental Research and Risk Assessment - A dam-break flood can cause catastrophic life losses due to the uncontrolled large amount of water. This paper aims to improve the estimation...     

Comparison of LLNF,ANN, and COA-ANN Techniques in Modeling the Uniaxial Compressive Strength and Static Young’s Modulus of Limestone of the Dalan Formation

Natural Resources Research - The uniaxial compressive strength and static Young’s modulus are among the key design parameters typically used in geotechnical engineering projects. In this...     

Identification of the excitation and reaction forces on offshore platforms using the random decrement technique

This paper describes a method to identify the parameters of the dynamic model of a fixed offshore platform subjected to wind-generated random waves using its stationary response. The structure is modeled as a single degree of freedom system. The parameters identified are the damping coefficient, the natural frequency, and the excitation. In addition, the moment and force acting on the foundation are also identified. The method uses the random decrement signature as a tool to identify the parameters in the equation of motion. Excellent agreements were obtained between the predicted and actual values of the parameters as well as for the reaction and moment at the platform's foundation. The method can be applied without any interruption to the operation of the offshore structure. The method is easy to apply, and uses inexpensive motion measurement instruments. The estimated force and moment can be used as a tool for an on-line foundation check.     

Analysis of hydrobiological pattern in the Bizerte lagoon (Tunisia)

This study deals with the use of a multivariate analysis method in order to understand the functioning of the Bizerte lagoon ecosystem. A set of hydrobiological parameters was collected during 10 monthly campaigns in 2004. A variant of the EOF (Empirical Orthogonal Function) technique is used to examine hydrobiological variability modes in this lagoon. The permanent features characterising the lagoon are obtained by applying the EOF technique to data after removing the annual cycle. Two major modes were obtained. The first one shows a contrast between the northern sector of the lagoon, influenced by the Mediterranean Sea, and the southern one influenced by continental waters. This mode is mostly prominent for temperature and salinity. The second mode shows a contrast between shallow waters along the coastal zones and the deep central area of the lagoon. This contrast is more pronounced towards the southwestern edge of the lagoon, a region of important freshwater input from the Tinja channel, which drifts towards the downstream area of Menzel Bourguiba. This second mode may also correspond to northward water circulation under southerly wind blowing frequently in summer. The spatial and temporal variability in the lagoon is highlighted by applying the EOF to the raw data without removing the annual cycle. A weight series is obtained for each variable by extracting the corresponding data and then projecting them on the corresponding eigenvector. Using this technique, only one mode was found dominant with more than 52% of the total variance. It was also found that the north–south contrast of temperature, salinity and phosphorous and the coast-centre contrast of Chlorophyll a are enhanced in summer. Other variables such as ammonia and nitrate also show significant annual cycles but with local patterns.     

Modified DRASTIC assessment for intrinsic vulnerability mapping of karst aquifers: a case study

Groundwater in karstic aquifers can be dangerously sensitive to contamination. In this paper, DRASTIC assessment was modified and applied, for the first time, to address the intrinsic vulnerability for karst aquifers. The theoretical weights of two of DRASTIC’s parameters (aquifer media and hydraulic conductivity) were modified through sensitivity analysis. Two tests of sensitivity analyses were carried out: the map removal and the single parameter sensitivity analyses. The modified assessment was applied for the karst aquifers underlying Ramallah District (Palestine) as a case study. The aquifer vulnerability map indicated that the case study area is under low, moderate and high vulnerability of groundwater to contamination. The vulnerability index can assist in the implementation of groundwater management strategies to prevent degradation of groundwater quality. The modified DRASTIC assessment has proven to be effective because it is relatively straightforward, use data that are commonly available or estimated and produces an end product that is easily interpreted.     

Time-fractional Burgers equation for dust acoustic waves in a two different temperatures dusty plasma

The reductive perturbation method has been used to derive the Burgers equation for dust acoustic shock waves in unmagnetized plasma having electrons, singly charged ions, hot and cold dust species with Boltzmann distributions for electrons and ions in the presence of the cold (hot) dust viscosity coefficients. The time-fractional Burgers equation is formulated using Euler-Lagrange variational technique and is solved using the variational-iteration method. The effect of time fractional parameter on the behavior of the shock waves in the dusty plasma has been investigated.     

Electrical resistivity imaging and hydrochemical analysis for groundwater investigation in Kuala Langat,Malaysia

ABSTRACT

Integrated two-dimensional electrical resistivity imaging (ERI) and hydrochemical surveys were used to investigate the groundwater alluvial aquifer in Kuala Langat, Malaysia. The study in the Langat basin considered the thickness of the aquifer, the depth of the bedrock, the regions influenced by seawater intrusion, and the monitoring of water levels. The resistivity imaging results show that the upper layer consists of clay, while the second layer is an aquifer whose thickness varies mostly in the range of 10–30 m, and in some cases extends to 40 m. The bedrock depth varies from 30 to 65 m. The chemical analyses were carried out on groundwater samples from nine boreholes collected between 2008 and 2012. The analyses indicate that the total dissolved solids (TDS) exceed 1000 mg L^-1 near the coastal area and are often less than 500 mg L^-1 further inland. The ERI and hydrochemical analyses reveal that groundwater in the study area, especially towards the coast, is a mixture of brackish and fresh waters.

EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR M.D. Fidelibus     

New Seismic Noise Models Obtained Using Very Broadband Stations

It has been two decades since the last comprehensive standard model of ambient earth noise was published Peterson (Observations and modelling of seismic background noise, US Geological Survey, open-file report 93–322, 1993). The PETERSON model was updated by analyzing the absolute quietest conditions for stations within the GSN (Berger et al. in J Geophys Res 109, 2005; Mcnamara and Buland in Bull Seism Soc Am 94:1517–1527, 2004; Ringler et al. in Seismol Res Lett 81(4) doi:10.1785/gssrl.81.4.605, 2010). Unfortunately, both the original model and the updated models did not include any deployed station in North Africa and Middle East, which reflects the noise levels within the desert environment of those regions. In this study, a survey was conducted to create a new seismic noise model from very broadband stations which recently deployed in North Africa. For this purpose, 1 year of continuous recording of seismic noise data of the Egyptian National Seismic Network (ENSN) was analyzed in order to create a new noise model. Seasonal and diurnal variations in noise spectra were recorded at each station. Moreover, we constructed a new noise model for each individual station. Finally, we obtained a new cumulative noise model for all the stations. We compared the new high-noise model (EHNM) and new low-noise model (ELNM) with both the high-noise model (NHNM) and low-noise model (NLNM) of Peterson (Observations and modelling of seismic background noise, US Geological Survey, open-file report 93–322, 1993). The obtained noise levels are considerably lower than low-noise model of Peterson (Observations and modelling of seismic background noise, US Geological Survey, open-file report 93–322, 1993) at ultra long period band (ULP band), but they are still below the high-noise model of Peterson (Observations and modelling of seismic background noise, US Geological Survey, open-file report 93–322, 1993). The results of this study could be considered as a first step to create permanent seismic noise models for North Africa and Middle East regions.