A seismological overview of the April 25, 2015 M<Subscript>w</Subscript>7.8 Nepal earthquake     

Mehdi Zare  Farnaz Kamranzad  Mona Lisa  Sudhir Rajaure 《Arabian Journal of Geosciences》2017,10(5):108

This paper aims to determine the damage distribution and to analyze the available strong motion records of the April 25, 2015 Nepal earthquake and its eight aftershocks. For this purpose, an earthquake investigation team was dispatched to Nepal from May 6 to 11, 2015 to evaluate the damages of the epicentral region and the four affected cities containing Kathmandu, Bhaktapur, Gorkha, and Pokhara. Based on the observations from the damages to the built environment, an iso-intensity map is prepared on the EMS-98 intensity scale in which the maximum intensity in the epicentral region is estimated to be about VIII. However, based on the geological and geotechnical evidences such as landslide volumes and ground fissures, the maximum intensity can be inferred about IX or X on the International Union for Quaternary Research (INQUA) intensity scale. In addition, the available strong motion data of the 2015 Nepal mainshock and its eight large aftershocks recorded at the KATNP accelerometric station in Kathmandu were processed and analyzed. In order to investigate the probable site effects, the Fourier amplitude spectra (FAS) of the horizontal north-south (N) and east-west (E) components and the average of them (H _avg) were divided to the FAS of the vertical (Z) component and thus, the \( \raisebox{1ex}{$ N$}\!\left/ \!\raisebox{-1ex}{$ Z$}\right. \), \( \raisebox{1ex}{$ E$}\!\left/ \!\raisebox{-1ex}{$ Z$}\right. \), \( \raisebox{1ex}{${H}_{\mathrm{avg}}$}\!\left/ \!\raisebox{-1ex}{$ Z$}\right. \) spectral ratios were calculated. Based on these horizontal to vertical spectral ratios, a low-frequency peak at about 0.2–0.3 Hz (3.5–5-s period) is observed clearly in all the records. Accordingly, the repeated results might imply site amplification due to the thick alluvial deposits and the high groundwater level at the KATNP accelerometric station within the Kathmandu basin. It should be noted that all the horizontal to vertical spectral ratios of the aftershocks show a high peak at around 1.5–3 Hz, which is missed in the horizontal to vertical spectral ratio of the mainshock. On the other hand, considering the low angle of the causative fault plane, a near-source directivity effect on the fault normal direction (here, the vertical component) of the April 25, 2015 mainshock rupture may exist. Therefore, vertical to horizontal spectral ratios (\( \raisebox{1ex}{$ Z$}\!\left/ \!\raisebox{-1ex}{$ N$}\right. \) and \( \raisebox{1ex}{$ Z$}\!\left/ \!\raisebox{-1ex}{$ E$}\right. \)) were also calculated to find the vertical peak more clearly. The figures confirmed a peak at the frequency of 1.5–3 Hz in the mainshock spectra which is not repeated on the aftershock spectra and thus can probably be attributed as the pulse of directivity effect toward Kathmandu. This inferred directivity pulse can be also well distinguished on the velocity and displacement time histories of the mainshock.  相似文献   

Efficient algorithms for the earth's gravitational potential and its partial derivatives for satellite prediction     

Mohamed Adel Sharaf  Mervat El-Sayed Awad  Mona A. Banaja 《Earth, Moon, and Planets》1989,47(2):171-192

In this paper, economical recursion formulae for the Earth's gravitational potential and its partial derivatives with respect to the Cartesian coordinates, and time will be established for any number and any type of the harmonic coefficients. General computational algorithms for their implementations on digital computers are also given.Now at the Department of Astronomy, King Abdul-Aziz Univ., Jeddah, Saudi Arabia.Now at the Department of Mathematics, Girls College of Education, Jeddah, Saudi Arabia.  相似文献   

Why did some larger benthic foraminifera become so large and flat?     

Pamela Hallock  Mona Seddighi 《Sedimentology》2022,69(1):74-87

Biostromes and low-relief bioherms, some of which are characterized by exceptionally large, flat specimens of larger benthic foraminifera, are common in Palaeogene and Miocene carbonates, most notably those deposited along the Neotethys Seaway and tropical Pacific islands. By incorporating insights from palaeoceanographic research and the biology of living larger benthic foraminifera, a scenario is proposed that can account for palaeontological and sedimentological features while augmenting previous interpretations. Sexual reproduction by gamete broadcasting is common in foraminiferal taxa, including extant Nummulitidae and Amphisteginidae. Resultant zygotes can develop into tiny, resistant, easily dispersed propagules that recruit in suitable benthic-environmental conditions. The role of algal symbiosis in the biology of larger benthic foraminifera is well-documented. Palaeoceanographically, such taxa proliferated during times of reduced thermal stratification of the oceans. In regions with exceptionally clear, nutrient-depleted waters, ‘twilight-zone’ light penetration was sufficient, at least intermittently, to support some photosynthesis. On outer-shelf or promontory sites at depths of ca 100 to 200 m, the tiny propagules of larger benthic foraminiferal species, incorporating algal symbionts with the lowest light requirements, could have settled and recruited, growing very slowly, nourished by feeding on bacteria and the limited photosynthate produced by their algal symbionts. Under such conditions, thin microspheric individuals of one or two larger benthic foraminiferal taxa could have survived and grown slowly over several years to very large shell diameters, seldom reproducing asexually. Resulting carbonate accumulation rates would have been very slow, such that even rare disturbances by currents, major storms or internal waves could have produced evidence of winnowing and sedimentary structures. The fossil evidence of such habitats should include biostromes or possibly low-relief bioherms of low diversity assemblages characterized by abundant, exceptionally large, flat, microspheric larger benthic foraminifera.  相似文献   

Indoor activity size distribution of the short-lived radon progeny     

Mostafa Yuness  Amer. Mohamed  Hyam Nazmy  Mona Moustafa  Moustafa Abd El-hady 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(1):167-174

Activity size distribution of the short-lived radon progeny in indoor air was measured continuously over several weeks. Two different measurement techniques were used: a direct measurement with a low-pressure Berner cascade impactor for attached fraction of ²¹⁴Pb and ²¹⁴Bi (≥100 nm) and an indirect determination based on measurement with a wire screen diffusion battery (unattached fraction 0.5–5 nm, ²¹⁸Po, ²¹⁴Pb). In parallel, the meteorological parameters like temperature, humidity were registered. Measured activity size distribution of radon progeny can be approximated by a sum of three log-normal distributions modes (nucleation, accumulation and coarse). The greatest activity fraction was adsorbed on aerosol particles in the accumulation size range (100–1000 nm) with activity median aerodynamic diameters (AMAD_a) and geometric standard deviations (GSD _a ) values of 250–500 nm, and 1.5–3.5, respectively. The influence of the weather conditions on the activity of the accumulation particles was not significant. In contrast to the results of measurements a small but significant fraction of the radon progeny (average value 5 %) was attached to coarse particles (>1000 nm). This fraction varied between 0 and 10 %. On the other hand, although the amount of unattached activities not more 10 % of the total activity, but is considered to yield about 50 % of the total radiation dose. The mean thermodynamic equivalent diameters of ²¹⁸Po and ²¹⁴Pb were determined to be 1.28 and 1.30 nm with relative mean geometric standard deviations of 1.30 and 1.24, respectively. Based on the obtained results of radon progeny size distributions (attached and unattached), the total deposition fractions of the human lung were evaluated by using a lung deposition model.  相似文献   

Vertical sediment fluxes and wave-induced sediment resuspension in a shallow-water coastal lagoon     

Lars Chresten Lund-Hansen  Mona Petersson  Wayan Nurjaya 《Estuaries and Coasts》1999,22(1):39-46

The present study describes variations in the vertical fluxes measured concurrently with sediment traps at both a shallow water (4 m) and a deeper water (7.5 m) position in a coastal lagoon in April 1995. A tripod equipped with five sediment traps (trap openings at 0.35 m, 0.75 m, 1.05 m, 1.40 m, and 1.80 m above the seabed) was placed at the shallow water position. This tripod was deployed three times during the study period and deployment periods varied between 2 d and 5 d. The second sediment trap, placed at the deep water position in the central part of the lagoon, measured vertical flux for intervals of 12 h at 1.4 m above the seabed. The horizontal distance between the sediment traps was 8 km. The average maximum vertical flux at the shallow water position reached 27.9 g m⁻² d⁻¹ during a period of high, westerly wind speeds, and a maximum vertical flux of 16.9 g m⁻² d⁻¹ was reached at the deep water position during a period of high, easterly wind speeds. Both strong resuspension events were closely related to increased wave shear stress derived from surface waves. Maximum wave-induced resuspension rate was 10 times higher at the shallow water position and 3.8 times higher at the deep water position compared with the net sedimentation rate in the lagoon. Small resuspension events occurred at the shallow water position during periods of increased current shear stress, Estimations of conditions for transport of sediment between shallow water and deep water showed that particles must be resuspended to a height between 3 m and 4 m and that current speeds must be higher than about 0.1 m s⁻¹. An average sedimentation rate of 3.8 g m⁻² d⁻¹ was obtained at the shallow water position during a period without wave shear stress and low current shear stress. This rate measured by sediment traps is similar to a net sedimentation rate in the lagoon of 4.4 g m⁻² d⁻¹, which was determined by radiocarbon dating of a sediment core (Kristensen et al. 1995).  相似文献   

Sustainable Development Goals (SDGs) Associated with Groundwater Over-Exploitation Vulnerability: Geographic Information System-Based Multi-criteria Decision Analysis     

Saqr  Ahmed M.  Ibrahim  Mona G.  Fujii  Manabu  Nasr  Mahmoud 《Natural Resources Research》2021,30(6):4255-4276

Natural Resources Research - Groundwater over-exploitation is related to various environmental, economic, and social aspects, which should be addressed comprehensively to support a sustainable...  相似文献   

Enhanced Methyl Orange Removal Using a Newly Isolated Bacterial Strain and Potassium‐Iodide‐Doped Hydroxyapatite Nanoparticles     

Mona Kilany  Essam H. Ibrahim  Ali Alshehri  Hamed A. Ghramh 《洁净——土壤、空气、水》2019,47(7)

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October 8, 2005 Pakistan Earthquake： Preliminary observations and report of an international conference     

Mona Lisa A. B. Kausar Azam A. Khwaja M. Qasim Jan 《《幕》》2006,29(3):206-208

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Implementation of a Petrographical and Petrophysical Workflow Protocol for Studying the Impact of Heterogeneity on the Rock Typing and Reservoir Quality of Reefal Limestone: A Case Study on the Nullipore Carbonates in the Gulf of Suez     

Mona G. SAFA  Bassem S. NABAWY  Ahmed M.K. BASAL  Mohammad A. OMRAN  Aref LASHIN 《《地质学报》英文版》2021,95(5):1746-1762

This study focuses on the heterogeneity of the middle Miocene syn-rift Belayim nullipore (reefal) marine sequences in the Gulf of Suez and its impacts on reservoir quality. The sequences consist of coralline algal reef limestones with a highly complex dual-porosity system of primary and secondary porosities of widely varying percentages. To achieve a precise mathematical modeling of these reservoir sequences, a workflow protocol was applied to separate these sequences into a number of hydraulic flow units (HFUs) and reservoir rock types (RRTs). This has been achieved by conducting a conventional core analysis on the nullipore marine sequence. To illustrate the heterogeneity of the nullipore reservoir, the Dykstra-Parsons coefficient (V) has been estimated (V = 0.91), indicating an extremely heterogeneous reservoir. A slight to high anisotropy (λk) has been assigned for the studied nullipore sequences. A stratigraphic modified Lorenz plot (SMLP) was applied to define the optimum number of HFUs and barriers/baffles in each of the studied wells. Integrating the permeability-porosity, reservoir quality index-normalized porosity index (RQI-NPI) and the RQI-flow zone indicator (RQI-FZI) plots, the discrete rock types (DRT) and the R35 techniques enable the discrimination of the reservoir sequences into 4 RRTs/HFUs. The RRT4 packstone samples are characterized by the best reservoir properties (moderate permeability anisotropy, with a good-to-fair reservoir quality index), whereas the RRT1 mudstone samples have the lowest flow and storage capacities, as well as the tightest reservoir quality.  相似文献   

The morphology and structure of the West O’Gorman Fracture Zone     

James S. McClain  Mona A. Wright 《Marine Geophysical Researches》1990,12(4):317-328

The West O’Gorman Fracture Zone is an unusual feature that lies between the Mathematician Ridge and the East Pacific Rise on crust generated on the East Pacific Rise between 4 and 9 million years ago. We made a reconnaissance gravity, magnetic and Sea Beam study of the zone with particular emphasis on its eastern (youngest) portion. That region is characterized by an elongate main trough, a prominent median ridge and other, smaller ridges and troughs. The structure has the appearance of large-offset fracture zone, possibly in a slow spreading environment. However, magnetic anomalies indicate that the offset, if any, is quite small, and the spreading rate during formation was fast. In addition, the magnetic profiles do not support earlier models for a difference in spreading rate north and south of the fracture. The morphology of the fracture zone suggests that flexure may be responsible for some of the topography; but gravity studies indicate some of the most prominent features of the fracture zone are at least partially compensated. The main trough is underlain by a thin crust (or high density body), similar to large-offset fracture zones in the Atlantic, while the median ridge is underlain by a thickened crust. Sea Beam data does not unambiguously resolve between volcanism or serpentinization of the upper mantle as a mechanism for isostatic compensation. Why the West O’Gorman exists remains enigmatic, but we speculate that the topographic expression of a fracture zone does not require a transform offset during formation. Perhaps the spreading ridge was magma starved for some reason, resulting in a thin crust that allowed water to penetrate and serpentinize portions of the upper mantle.  相似文献