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101.
Shabana Khan Jyoti L. Mishra Kuna-hui Elaine Lin Emma E. H. Doyle 《Natural Hazards》2017,85(3):1709-1722
We have studied the attenuation characteristics of eastern Himalaya and southern Tibet by using local earthquake data set that consists of 123 well-located events, recorded by the Himalayan Nepal Tibet Seismic Experiment operated during 2001–2003. We have used single backscattering model to calculate frequency-dependent values of coda Q (\(Q_\mathrm{c}\)). The estimation of \(Q_\mathrm{c}\) is made at central frequencies 2, 4, 8 and 12 Hz through five lapse time windows from 10 to 50 s starting at double the travel time of the S-wave. The observed \(Q_\mathrm{c}\) is found to be strongly frequency-dependent and follows a similar trend as observed in other tectonically active parts of the Himalaya. The trend of variation of \(Q_\mathrm{c}\) with lapse time and the corresponding apparent depths is also studied. Increase in \(Q_\mathrm{c}\) values with the lapse time suggests that the deeper part of the study region is less heterogeneous than the shallower part. The observed values of \(Q_0\) (\(Q_\mathrm{c}\) at 1 Hz) and frequency parameter n indicate that the medium beneath the study area is highly heterogeneous and tectonically very active. A regionalization of the estimated \(Q_0\) is carried out, and a contour map is prepared for the whole region. Some segments of Lesser Himalaya and Sub-Himalaya exhibit very low \(Q_0\) , while the whole Tethyan Himalaya and some parts of Greater Himalaya are characterized by low \(Q_0\) values. Our results are comparable with those obtained from tectonically active regions in the world. 相似文献
102.
Jewgenij Torizin Michael Fuchs Adnan Alam Awan Ijaz Ahmad Sardar Saeed Akhtar Simon Sadiq Asif Razzak Daniel Weggenmann Faseeh Fawad Nimra Khalid Faisan Sabir Ahsan Jamal Khan 《Natural Hazards》2017,87(2):757-771
This paper presents laboratory experiments and numerical simulations of effects of submerged obstacles on tsunami-like solitary wave and its run-up. This study was carried out for the breaking and non-breaking solitary waves on 1:19.85 uniform slope which contains a submerged obstacle. New laboratory experiments are performed to describe the mitigation of tsunami amplitude and run-up under the effect of submerged obstacles. We are based on experimental results obtained to validate the numerical model. The numerical modeling using COULWAVE aims essentially to show the effect of the obstacle on the shape of solitary wave and the limit of this effect. Using a multiple nonlinear regression, we have determined a model to estimate height of run-up according to the amplitude of the wave and the obstacle peak depth. 相似文献
103.
The main objective of this paper was to investigate the dewatering behaviour of a clayey uranium ore slurry. The slurry (containing 28% clay size) exhibited moderate water adsorption (w l = 83% and w p = 30%). Primarily composed of muscovite (46%) and quartz (30%), the clay minerals included illite (8%), chlorite (5%) and kaolinite (2%) alongside a CEC of 41 (cmol(+)/kg) with Ca2+ and Mg2+ as the dominant cations. Likewise, the high EC (17,600 μS/cm) and ionic strength (1.15 mol/L) indicated a flocculated microstructure due to the presence of SO4 2? (22,600 mg/L) and Mg2+ (1340 mg/L) in the slurry water. Settling included sedimentation and consolidation at low initial solids condition (25–35%) whereas only consolidation was observed at high initial solids contents (40–50%). The average k reduced from 1.2 × 10?6 m/s (initial s = 25%) to 5.3 × 10?8 m/s (initial s = 50%) along with a void ratio reduction from 7.4 to 2.6. Due to thixotropic strength, volume compressibility during consolidation showed apparent pre-consolidation at low effective stress (0.3–2 kPa) with a reduction in void ratio from 2.6 to 2.5. The e s was found to be 2.46 at σ′ = 2 kPa and was followed by a steeper slope with the void ratio reducing to 2.1 at σ′ = 31 kPa. Likewise, the hydraulic conductivity during consolidation decreased from 2.6 × 10?9 m/s (at e = 2.6) to 2.0 × 10?10 m/s (at e = 2.1). 相似文献
104.
Silicate‐oxide mineral chemistry of mafic–ultramafic rocks as an indicator of the roots of an island arc: The Chilas Complex,Kohistan (Pakistan) 
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下载免费PDF全文 The Chilas Complex is a major lower crustal component of the Cretaceous Kohistan island arc and one of the largest exposed slices of arc magma chamber in the world. Covering more than 8000 km2, it reaches a current tectonic width of around 40 km. It was emplaced at 85 Ma during rifting of the arc soon after the collision of the arc with the Karakoram plate. Over 85% of the Complex comprises homogeneous, olivine‐free gabbronorite and subordinate orthopyroxene–quartz diorite association (MGNA), which contains bodies of up to 30 km2 of ultramafic–mafic–anorthositic association (UMAA) rocks. Primary cumulate textures, igneous layering, and sedimentary structures are well preserved in layered parts of the UMAA in spite of pervasive granulite facies metamorphism. Mineral analyses show that the UMAA is characterized by more magnesian and more aluminous pyroxene and more calcic plagioclase than those in the MGNA. High modal abundances of orthopyroxene, magnetite and ilmenite (in MGNA), general Mg–Fe–Al spatial variations, and an MFA plot of whole‐rock analyses suggest a calc‐alkaline origin for the Complex. Projection of the pyroxene compositions on the Wo–En–Fs face is akin to those of pyroxenes from island arcs gabbros. The presence of highly calcic plagioclase and hornblende in UMAA is indicative of hydrous parental arc magma. The complex may be a product of two‐stage partial melting of a rising mantle diaper. The MGNA rocks represent the earlier phase melting, whereas the UMAA magma resulted from the melting of the same source depleted by the extraction of the earlier melt phase. Some of the massive peridotites in the UMAA may either be cumulates or represent metasomatized and remobilized upper mantle. The Chilas Complex shows similarities with many other (supra)subduction‐related mafic–ultramafic complexes worldwide. 相似文献
105.
106.
Khadija Semhi Osman A. E. Abdalla Salah Al Khirbash Tabisam Khan Salim Asaidi Sardar Farooq 《Arabian Journal of Geosciences》2009,2(2):143-150
Groundwater samples from six wells and various species of plants from soils developed on ophiolites were collected from an arid area (AlKhod area, Oman) and analyzed for trace elements including rare earth elements (REEs). The distribution patterns of REEs in plants indicated an enrichment in middle REEs (MREEs?=?Sm to Dy) and heavy REEs (HREEs?=?Ho to Lu), when they are normalized to the REE composition of the Post Archean Australian Shale (PAAS), with a significant negative anomaly in Ce and a positive anomaly in Eu. Compared to Oman ophiolites, the REEs in different species of plants are depleted in Ce and enriched in MREEs and slightly enriched in light REE (LREE?=?from La to Nd). Relative to PAAS, the distribution of REEs in groundwaters revealed similar patterns to the REE distribution in plants. The distribution patterns of REEs in plants relative to those in waters are nearly flat. These patterns suggest that the transfer of REEs from soil solutions to the groundwaters in Oman occurs without any significant fractionation. 相似文献
107.
ABSTRACTSeries of observed flood intervals, defined as the time intervals between successive flood peaks over a threshold, were extracted directly from 11 approximately 100-year streamflow datasets from Queensland, Australia. A range of discharge thresholds were analysed that correspond to return periods of approximately 3.7 months to 6.3 years. Flood interval histograms at South East Queensland gauges were consistently unimodal whereas those of the North and Central Queensland sites were often multimodal. The exponential probability distribution (pd) is often used to describe interval exceedence probabilities, but fitting utilizing the Anderson-Darling statistic found little evidence that it is the most suitable. The fatigue life pd dominated sub-year return periods (<1 year), often transitioning to a log Pearson 3 pd at above-year return periods. Fatigue life pd is used in analysis of the lifetime to structural failure when a threshold is exceeded, and this paper demonstrates its relevance also to the elapsed time between above-threshold floods. At most sites, the interval medians were substantially less than the means for sub-year return periods. Statistically the median is a better measure of the central tendency of skewed distributions but the mean is generally used in practice to describe the classical concept of flood return period.
Editor Z.W. Kundzewicz; Associate editor I. Nalbantis 相似文献
108.
H. S. Mandal A. K. Shukla P. K. Khan O. P. Mishra 《Pure and Applied Geophysics》2013,170(12):2139-2161
The Son-Narmada-Tapti lineament and its surroundings of Central India (CI) is the second most important tectonic regime following the converging margin along Himalayas-Myanmar-Andaman of the Indian sub-continent, which attracted several geoscientists to assess its seismic hazard potential. Our study area, a part of CI, is bounded between latitudes 18°–26°N and longitudes 73°–83°E, representing a stable part of Peninsular India. Past damaging moderate magnitude earthquakes as well as continuing microseismicity in the area provided enough data for seismological study. Our estimates based on regional Gutenberg–Richter relationship showed lower b values (i.e., between 0.68 and 0.76) from the average for the study area. The Probabilistic Seismic Hazard Analysis carried out over the area with a radius of ~300 km encircling Bhopal yielded a conspicuous relationship between earthquake return period (T) and peak ground acceleration (PGA). Analyses of T and PGA shows that PGA value at bedrock varies from 0.08 to 0.15 g for 10 % (T = 475 years) and 2 % (T = 2,475 years) probabilities exceeding 50 years, respectively. We establish the empirical relationships $ {\text{ZPA}}_{(T = 475)} = 0.1146\;[V_{\text{s}} (30)]^{ - 0.2924}, $ and $ {\text{ZPA}}_{(T = 2475)} = 0.2053\;[V_{\text{s}} (30)]^{ - 0.2426} $ between zero period acceleration (ZPA) and shear wave velocity up to a depth of 30 m [V s (30)] for the two different return periods. These demonstrate that the ZPA values decrease with increasing shear wave velocity, suggesting a diagnostic indicator for designing the structures at a specific site of interest. The predictive designed response spectra generated at a site for periods up to 4.0 s at 10 and 2 % probability of exceedance of ground motion for 50 years can be used for designing duration dependent structures of variable vertical dimension. We infer that this concept of assimilating uniform hazard response spectra and predictive design at 10 and 2 % probability of exceedance in 50 years at 5 % damping at bedrocks of different categories may offer potential inputs for designing earthquake resistant structures of variable dimensions for the CI region under the National Earthquake Hazard Reduction Program for India. 相似文献
109.
Abstract The Coupled Routing and Excess STorage model (CREST, jointly developed by the University of Oklahoma and NASA SERVIR) is a distributed hydrological model developed to simulate the spatial and temporal variation of land surface, and subsurface water fluxes and storages by cell-to-cell simulation. CREST's distinguishing characteristics include: (1) distributed rainfall–runoff generation and cell-to-cell routing; (2) coupled runoff generation and routing via three feedback mechanisms; and (3) representation of sub-grid cell variability of soil moisture storage capacity and sub-grid cell routing (via linear reservoirs). The coupling between the runoff generation and routing mechanisms allows detailed and realistic treatment of hydrological variables such as soil moisture. Furthermore, the representation of soil moisture variability and routing processes at the sub-grid scale enables the CREST model to be readily scalable to multi-scale modelling research. This paper presents the model development and demonstrates its applicability for a case study in the Nzoia basin located in Lake Victoria, Africa. Citation Wang, J., Yang, H., Li, L., Gourley, J. J., Sadiq, I. K., Yilmaz, K. K., Adler, R. F., Policelli, F. S., Habib, S., Irwn, D., Limaye, A. S., Korme, T. &; Okello, L. (2011) The coupled routing and excess storage (CREST) distributed hydrological model. Hydrol. Sci. J. 56(1), 84–98. 相似文献
110.
A three dimensional rectangular grid model is applied to resolve the temperature–salinity dynamics of Ruwais, a segment of the UAE coast which is well known as dense water formation zone. The model employs a heat flux module and a turbulence closure scheme that facilitate realistic calculation of temperature–salinity dynamics. A field survey campaign is carried out to support the modeling study, involving measurements of tide, currents, temperature, and salinity. Investigation is done for two meteorologically extreme conditions, i.e. summer and winter. The model study showed that the western flux develops an anticlockwise circulation in the study area. The water industrial discharges elevated the temperature and salinity of the water near the southeastern shoreline. This water mass propagated towards north under the influence of gravity. 相似文献