A secondary sludge flow hazard induced by shallow-source seismic activity in karst mining area,Guangxi, South China: localized karstification in anticline     

Zhiyong Li  Xiguang Li  Adil S. Mohammed  Mike Vorkink  Xiaomin Yan 《Natural Hazards》2016,83(1):75-95

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Forced folding of the neoautochthonous Late Cretaceous–Early Tertiary sequence at the western end of the Hatta Zone, Northern Oman Mountains     

Mohammed Warrak 《Arabian Journal of Geosciences》2010,3(4):369-393

At the western end of the Hatta Zone (the Jebel Rawdha area), Northern Oman Mountains, the neoautochthonous Late Cretaceous–Early Tertiary sequence (“cover”) lies with an angular unconformity on the obducted Semail ophiolite, Haybi Complex and Sumeini Group (“basement”). Structural analysis of the faults in both the basement and cover sequences has shown that they are similar in type and configuration to those that develop in a transpressional left-lateral strike-slip deformational regime (a restraining bend) that is characterised by the dominance of the dip-slip component over the strike-slip component. The WNW–ESE (P_o) faults together with the linking NW–SE (P) faults have divided the basement into elongated blocks. These blocks, in turn, are subdivided by transverse normal faults into horst and graben sub-blocks. The cover sequence is gently folded into a generally WNW–ESE-trending ‘Main’ folds and NE–SW-trending ‘Cross’ folds superimposed on them. These folds appear to be dominantly forced folds that developed as a result of repeated uplift and depression of basement blocks. Their trends correspond to the trends of the subjacent basement blocks. Hence, the Jebel Rawdha folds trend differently from other post-obduction major folds in the foreland region of the Northern Oman Mountains, such as the Hafit and Jebel Faiyah folds. Differences in stratigraphic thicknesses and lateral facies changes of the cover sequence within the blocks and sub-blocks indicate that the earliest differential movement of the blocks must have occurred during the early Maastrichtian, and the latest movement in post-mid-Eocene. Thus, pushing back the initiation of the post-obduction deformation in the Northern Oman Mountains to the early Maastrichtian.  相似文献   

Hydrogeochemical processes in a shallow coastal plain sand aquifer and tidal river systems (Calabar,Southeastern Nigeria): tracking wastewater and seawater pollution in ground and river waters   总被引：2，自引：2，他引：0  

A. E. Edet  R. H. Worden  E. A. Mohammed  M. R. Preston 《Environmental Earth Sciences》2012,65(7):1933-1953

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An experimental study of dispersion of an interactive tracer in chemically heterogeneous medium at a column scale     

Fatiha Benmahdi  Safia Semra  Mounira Kolli  Mohammed Bouhelassa 《水文研究》2020,34(20):3932-3940

This paper aims at examining the increase of phenol adsorption breakthrough curves spreading caused by the chemical heterogeneity of granular activated carbon fixed beds. The local and the thermodynamic equilibrium assumption, as well as the nonlinear adsorption obeying to Langmuir isotherm, are considered. This study particularly tempts to link the reduced variance of phenol breakthrough curves to a measurable quantifying parameter of the chemical heterogeneity. The investigated artificial heterogeneous media are prepared by alternating layers of two types of granular activated carbon, active and non-active ones, that have similar physical properties. On the one hand, the chemical heterogeneity is quantified by the active layer relative thickness of the column length, l₁/L. On the other hand, it is quantified by the mean value of the probability distribution γ. The latter also represents the mean active grains mass ratio of the total medium mass, hence the medium mean capacity. The obtained results show an increase in the reduced variance and thus the effective global dispersion with the heterogeneity; the increase is as important as the medium capacity decreases. However, the dispersion increase achieves a limit value, even when the heterogeneity increases. The results are statistically modelled using a regression equation function of the capacity variation in terms of γ and the chemical heterogeneity in terms of l₁/L. The relationship combining the medium capacity and the chemical heterogeneity is obtained. The relationship implicitly takes into account the effect of the column length.  相似文献   

Local outlier factor as part of a workflow for detecting and attenuating blending noise in simultaneously acquired data     

Woodon Jeong  Constantinos Tsingas  Mohammed S. Almubarak 《Geophysical Prospecting》2020,68(5):1523-1539

A number of deblending methods and workflows have been reported in the past decades to eliminate the source interference noise recorded during a simultaneous shooting acquisition. It is common that denoising algorithms focusing on optimizing coherency and weighting down/ignoring outliers can be considered as deblending tools. Such algorithms are not only enforcing coherency but also handling outliers either explicitly or implicitly. In this paper, we present a novel approach based on detecting amplitude outliers and its application on deblending based on a local outlier factor that assigns an outlier-ness (i.e. a degree of being an outlier) to each sample of the data. A local outlier factor algorithm quantifies outlier-ness for an object in a data set based on the degree of isolation compared with its locally neighbouring objects. Assuming that the seismic pre-stack data acquired by simultaneous shooting are composed of a set of non-outliers and outliers, the local outlier factor algorithm evaluates the outlier-ness of each object. Therefore, we can separate the data set into blending noise (i.e. outlier) and signal (i.e. non-outlier) components. By applying a proper threshold, objects having high local outlier factors are labelled as outlier/blending noise, and the corresponding data sample could be replaced by zero or a statistically adequate value. Beginning with an explanation of parameter definitions and properties of local outlier factor, we investigate the feasibility of a local outlier factor application on seismic deblending by analysing the parameters of local outlier factor and suggesting specific deblending strategies. Field data examples recorded during simultaneous shooting acquisition show that the local outlier factor algorithm combined with a thresholding can detect and attenuate blending noise. Although the local outlier factor application on deblending shows a few shortcomings, it is consequently noted that the local outlier factor application in this paper obviously achieves benefits in terms of detecting and attenuating blending noise and paves the way for further geophysical applications.  相似文献   

Device-free human micro-activity recognition method using WiFi signals     

Mohammed A. A. Al-qaness 《地球空间信息科学学报》2019,22(2):128-137

ABSTRACT

Human activity tracking plays a vital role in human–computer interaction. Traditional human activity recognition (HAR) methods adopt special devices, such as cameras and sensors, to track both macro- and micro-activities. Recently, wireless signals have been exploited to track human motion and activities in indoor environments without additional equipment. This study proposes a device-free WiFi-based micro-activity recognition method that leverages the channel state information (CSI) of wireless signals. Different from existed CSI-based micro-activity recognition methods, the proposed method extracts both amplitude and phase information from CSI, thereby providing more information and increasing detection accuracy. The proposed method harnesses an effective signal processing technique to reveal the unique patterns of each activity. We applied a machine learning algorithm to recognize the proposed micro-activities. The proposed method has been evaluated in both line of sight (LOS) and none line of sight (NLOS) scenarios, and the empirical results demonstrate the effectiveness of the proposed method with several users.  相似文献   

Site dependent and spatially varying response spectra     

Djilali Berkane  Hakima  Harichane  Zamila  Çelebi  Erkan  Elachachi  Sidi Mohammed 《地震工程与工程振动(英文版)》2019,18(3):497-509

The goal of this study is to provide a stochastic method to investigate the effects of the randomness of soil properties due to their natural spatial variability on the response spectra spatial variation at sites with varying conditions. For this purpose, Monte Carlo Simulations are used to include the variability of both incident ground motion and soil parameters in the response spectra by mean of an appropriate coherency loss function and a site-dependent transfer function, respectively. The approach is built on the assumption of vertical propagation of SH type waves in soil strata with uncertain parameters. The response spectra are obtained by numerical integration of the governing equation of a single-degree-of-freedom(SDOF) system under non-stationary site-dependent and spatially varying ground motion accelerations simulated with non-uniform spectral densities and coherency loss functions. Numerical examples showed that randomness of soil properties significantly affects the amplitudes of the response spectra, indicating that as the heterogeneity induced by the randomness of the parameters of the medium increases, the spectral ordinates attenuate.  相似文献   

Petrography,geochemistry, and provenance of the Chalki rocks in Kurdistan region,North Iraq     

Sarmad Asi Ali  Muhamed Fakhri Omer  Ahmed Mohammed Aqrawi 《Arabian Journal of Geosciences》2016,9(8):524

Outcrops of the Paleozoic Chalki volcanic rocks are restricted to part of the northern Thrust Zone of Iraq close to Iraqi-Turkish border. Petrographically, the volcanic rocks from the Chalki area are mainly layered, appearing fresh in the field and exhibiting some basaltic lava flows. Porphyritic, amygdaloidal, and microlite-porphyric are the main observed textures. Phenocrysts of primary phases (i.e., olivine, iron oxides) are in a groundmass of feldspars and clinopyroxene. Chalki Formation is intercalated with Pirispiki Formation which consists of thin to medium bedded, greenish gray marl, red mudstone, and veins of calcite. The Chalki rocks are mafic of theolitic basalt type. Geochemically, they have high chromium and nickel concentrations in most samples. Rare earth element (REE) patterns illustrate parallel to sub-parallel, moderately fractionated REE patterns. The low heavy REE (HREE) contents in the studied samples appear to be due to partial melting of metamorphosed oceanic crust leaving HREE-rich accessory minerals (i.e., garnet) as a residual phase in the source. No Eu anomalies were observed in the Chalki samples which may indicate a back-arc basin pattern. The non-subduction signature of the Chalki rocks is confirmed by the Nb/Yb versus Th/Yb diagram, which shows that most of the studied rocks fall in the compositional field of non-arc-related rocks—well within the field of the mid-ocean ridge basalt (MORB)-ocean island basalt (OIB) mantle array.  相似文献   

Seismic reflection imaging of active faults and their tectonic behavior in the Northern Moroccan margin. Is the Nekor fault a pure strike-slip fault?     

Ghizlane?BouskriEmail author  Mohammed?Elabbassi  Abdellah?Ammar  Driss?El Ouai  Mimoun?Harnafi 《Arabian Journal of Geosciences》2016,9(15):666

The study of 1000-km seismic reflection profiles, along the Northern Moroccan margin, allowed browsing new imaging in detail about the regional geological structures and their functioning. To achieve this goal, we elaborated a high-resolution depth model and a global tectonic sketch. The influence of recent tectonic activity is manifested by normal and strike-slip faults, trending mainly 70° N and 125° N. In this segment, the Nekor strike-slip fault seems to be connected to a secondary major fault system that changes direction from 30° N to 70° N, and changing behavior to left-lateral strike-slip fault with normal component. Analysis of local seismic activity recorded from 1990 to 2014 with moderate magnitudes activity shows alignments in clear superposition with the detected active faults in seismic reflection lines.  相似文献   

Optical and radiative properties of aerosols over Abu Dhabi in the United Arab Emirates     

S Naseema Beegum  Haifa Ben Romdhane  Mohammed Tauha Ali  Peter Armstrong  Hosni Ghedira 《Journal of Earth System Science》2016,125(8):1579-1602

The present study is on the aerosol optical and radiative properties in the short-wave radiation and its climate implications at the arid city of Abu Dhabi (24.42 ^°N, 54.61 ^°E, 4.5 m MSL), in the United Arab Emirates. The direct aerosol radiative forcings (ARF) in the short-wave region at the top (TOA) and bottom of the atmosphere (BOA) are estimated using a hybrid approach, making use of discrete ordinate radiative transfer method in conjunction with the short-wave flux and spectral aerosol optical depth (AOD) measurements, over a period of 3 years (June 2012–July 2015), at Abu Dhabi located at the south-west coast of the Arabian Gulf. The inferred microphysical properties of aerosols at the measurement site indicate strong seasonal variations from the dominance of coarse mode mineral dust aerosols during spring (March–May) and summer (June–September), to the abundance of fine/accumulation mode aerosols mainly from combustion of fossil-fuel and bio-fuel during autumn (October–November) and winter (December–February) seasons. The monthly mean diurnally averaged ARF at the BOA (TOA) varies from ?13.2 Wm^?2 (～?0.96 Wm^?2) in November to ?39.4 Wm^?2 (?11.4 Wm^?2) in August with higher magnitudes of the forcing values during spring/summer seasons and lower values during autumn/winter seasons. The atmospheric aerosol forcing varies from + 12.2 Wm^?2 (November) to 28.2 Wm^?2 (June) with higher values throughout the spring and summer seasons, suggesting the importance of mineral dust aerosols towards the solar dimming. Seasonally, highest values of the forcing efficiency at the surface are observed in spring (?85.0 ± 4.1 W m^?2 τ ^?1) followed closely by winter (?79.2 ± 7.1 W m^?2 τ ^?1) and the lowest values during autumn season (?54 ± 4.3 W m^?2 τ ^?1). The study concludes with the variations of the atmospheric heating rates induced by the forcing. Highest heating rate is observed in June (0.39 K day ^?1) and the lowest in November (0.17 K day ^?1) and the temporal variability of this parameter is linearly associated with the aerosol absorption index.  相似文献