Recurring emergence of the mud islands on shelf of the Arabian Sea along the Makran coast of Pakistan – Historical perspective using remote sensing techniques     

Akhtar M. Kassi  Huseyin Bayraktar  Shuhab D. Khan  Aimal K. Kasi 《Journal of the Geological Society of India》2017,90(2):201-208

Recurring emergences of mud islands on shelf of the Arabian Sea, along the Makran coast of Pakistan are now known to be submarine mud volcanoes. They are expressions of enhanced extrusions of fluidized mud and gases coupled with compressional tectonics in convergent margin settings. Since 1945 the Malan island has emerged four times, and some other mud islands have also been emerging repeatedly, at their own positions.The first known emergence, during November 1945, was concurrent with an earthquake of magnitude 8.0 (M8.0), the 2^nd and 3^rd emergences, in March 1999 and November 2010 respectively, were not related apparently with earthquakes. The 4^th emergence concurred with the Awaran earthquake (M7.7) of 24th September 2013. Landsat images of March 1999 and November 2010 emergences indicate appearance of round-shaped island of 4.4 and 5.2 hectare area, followed by erosion and disappearance. The island was composed of mud breccias and circular vents spewing mud slurry and methane gas.The emergence of Malan island, in March 1999 and November 2010 was compared with earthquake data before and after the emergences. The earthquakes data, two years before March 1999 and November 2010 emergences and two years afterwards, shows correlation with both small and large earthquakes, prior to the emergence, in the radius of over 400 km. It is proposed that mud islands develop in response to the episodes of enhanced mud extrusion, which inturn are related with the enhanced compressional and/or seismic events. These events are followed by periods of relative quiescence characterized by normal activity of mud extrusion and marine erosion.  相似文献   

A three-dimensional finite element program for brittle bimodular rock-like materials     

Akhtar S. Khan  Si Yuan 《国际地质力学数值与分析法杂志》1988,12(6):599-609

The present paper models the behaviour of bimodular materials (materials with different tensile and compressive moduli) by using a three-dimensional finite element method. Since there is no explicit and definite expression for the shear modulus G of bimodular materials, the analysis starts with a 3 × 3 elasticity matrix in the principal stress coordinate system, and then uses a transformation from principal to Cartesian coordinates to obtain the 6 × 6 elasticity matrix. A corresponding iterative technique is proposed, and multiloading sequences in non-proportionate loading—which need more iterations because of the non-linear elastic property—are also discussed. Numerical examples are presented which show good agreement with analytical results.  相似文献   

Some economic characteristics of animal husbandry in Pakistan     

Akhtar Husain Siddiqi 《GeoJournal》1977,1(5):33-40

In spite of the predominance of agriculture in the economy of Pakistan, animal raising is the most neglected industry in the country. The study points out some of the reasons for such neglect and lack of enthusiasm in organizing the cattle industry. Cost and return method has been used to relate the importance of crops over livestock in the farm economy.  相似文献   

    

R. Akhtar  A. Learmonth  Milton Keynes 《GeoJournal》1977,1(5):69-79

Summary and Tentative Conclusion The eradication campaign faltered, for historical reasons some of which are tentatively suggested above and which would be worthy of fuller study as an important part of recent medical history; it is one of those historical topics so intertwined with political and social history that an interdisciplinary approach would be fruitful — if the necessary documents could be made accessible, in India and perhaps in international organisations and subscribing government archives too.Once the campaign faltered malaria seems to have diffused from the four foci suggested, the Kutch saltmarsh area and the hill-forest tracts of Madhya, Orissa and Assam. The role of wet years in areas normally arid, semi-arid or only moderately humid seems crucial in the diffusion process, and if the gaps in the rainfall anomaly maps can be filled we shall try to provide a more rigorous analysis of this relationship. Some humid and perhumid areas of high agricultural development, and dense or very dense rural populations, and one or two areas of considerable industrial and urban development like Greater Calcutta and nearby towns, seem so far to be happily little affected by the diffusion of malaria, even though as late as 1948 some including much of West Bengal were hyperendemic areas. It remains to be established by detailed studies if these areas are better prepared in some way — natural immunity must have faded especially in the considerable proportion of young people who have been born since malaria eradication was almost within grasp; or are they so far comparatively fortunate through some chances of the diffusion pattern?Urban malaria, and one might sayAnopheles stephensi malaria, is probably more widespread and more significant as an important public health problem than in former times. Once more the need for detailed local studies is clear.It is important to re-read the introductory paragraph of this paper. The fiftyfold increase from 100000 to 5 million cases represents a sharp resurgence but the 5 million cases of 1975 and 1976, and few scores of recorded deaths, still represent a remarkable achievement as compared with the 75 million cases and 800,000 deaths a year at the time of Independence. From over 5 million in 1976 to 10 million in the first nine months of 1977, however, is a quite disquieting increase. If complacence did indeed play a part in the crucial years of resurgence in the late 1960s, it is unlikely to continue today in medical circles. One can only hope that politicians will take the issue seriously. Studies of the economic, educational and demographic impact of the resurgence may help them to do so.  相似文献   

Artificial neural network application to estimate kinematic soil pile interaction response parameters   总被引：1，自引：0，他引：1  

Irshad Ahmad  M. Hesham El Naggar  Akhtar Naeem Khan   《Soil Dynamics and Earthquake Engineering》2007,27(9):892-905

Six artificial neural network (ANN) models are developed to predict various response parameters of kinematic soil pile interaction. These responses include (1) kinematic response factors for free and fixed head piles in homogenous soil layer to derive foundation input motion (2) normalized bending moment at fixed head of pile in homogenous soil layer (3) normalized kinematic pile moment at the interface of two soil layers of sharply different soil stiffnesses. These ANN models represent simple solutions that can be implemented in a simple calculator capable of matrix operation and bypass the site response analysis and the complex wave diffraction analysis. The data required for ANN training is generated using beam on dynamic Winkler formulation (BDWF). Fifty percent of the data is used to train the ANN models while remaining 50% is used to test the ANN models. The trained ANN models show good agreement with BDWF results.  相似文献   

Impacts of Overpopulation on Natural Environment with Special Reference to Bangladesh, a Developing Country in Gondwana Terrain     

Afia Akhtar  M. Nurul Hasan 《Gondwana Research》2001,4(4):562

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A Paleogeographic and Depositional Model for the Neogene Fluvial Succession,Pishin Belt,Northwest Pakistan: Effect of Post Collisional Tectonics on Sedimentation in a Peripheral Foreland Setting     

Aimal K. KASI  Akhtar M. KASSI  Muhammad UMAR  Henrik FRIIS  Mohibullah MOHIBULLAH  Razzaq A. MANAN 《《地质学报》英文版》2018,92(2):499-518

Detailed facies analysis of the Neogene successions of the Pishin Belt (Katawaz Basin) has enabled documentation of successive depositional systems and paleogeographic settings of the basin formed by the collision of the northwestern continental margin of the Indian Plate and the Afghan Block. During the Early Miocene, subaerial sedimentation started after the final closure of the Katawaz Remnant Ocean. Based on detailed field data, twelve facies were recognized in Neogene successions exposed in the Pishin Belt. These facies were further organized into four facies associations i.e. channels, crevasse splay, natural levee and floodplain facies associations. Facies associations and variations provided ample evidence to recognize a number of fluvial architectural components in the succession e.g., low‐sinuosity sandy braided river, mixed‐load meandering, high‐sinuosity meandering channels, single‐story sandstone and/or conglomerate channels, lateral accretion surfaces (point bars) and alluvial fans. Neogene sedimentation in the Pishin Belt was mainly controlled by active tectonism and thrusting in response to the oblique collision of the Indian Plate with the Afghan Block of the Eurasian Plate along the Chaman‐Nushki Fault. Post Miocene deformation of these formations successively caused them to contribute as an additional source terrain for the younger formations.  相似文献   

Characteristics,modification and environmental application of Yemen’s natural bentonite     

Aref Alshameri  Alkhafaji R.Abood  Chunjie Yan  Akhtar Malik Muhammad 《Arabian Journal of Geosciences》2014,7(3):841-853

The bentonite deposit of Lahij Province, Yemen, has very promising commercial applications due to its mineralogy and physical and chemical properties. It was examined to determine its mineralogical composition, chemical and physical properties of the bentonite deposit, purity and sodium-exchanged bentonite. Modified bentonite was synthesized by exchanging cetyltrimethylammonium cations for inorganic ions on the bentonite and its adsorption properties for ammonium were characterized in batch experiments. Analytical methods were carried out to study the bentonite comprising X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy, chemical analysis and kinetic and isotherm models were also tested. The results have shown that the purification of bentonite resulted in a bentonite fractions of the total sample composed of montmorillonite and <5 % quartz. The XRD data showed that the interlayer spacing (d ₀₀₁) of bentonite decreased from 15.3 to 12.5 Å and then increased to 19.7 Å. Moreover, high cation exchange capacity, good water absorption and high swelling capacity were also obtained. The results have shown that the modified bentonite was more effective than the natural bentonite for ammonium removal. In addition to that, pseudo-second-order kinetic model, Freundlich and the Langmuir models described the adsorption kinetics and isotherm well. It was concluded that Yemen (Alaslef) bentonite can be potential adsorbents for ammonium removal.  相似文献   

Similarity solutions for imploding shocks in non-ideal magnetogasdynamics     

L. P. Singh  M. Singh  Akmal Husain 《Astrophysics and Space Science》2011,331(2):597-603

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Mineral and chemical composition of Karak mudstone, Kohat Plateau, Pakistan: implications for smectite-illitization and provenance   总被引：1，自引：0，他引：1  

Akhtar Ali Saleemi  Zulfiqar Ahmed   《Sedimentary Geology》2000,130(3-4):229-247

The Karak mudstone interbedded in an Eocene evaporite sequence, is dominated by R-1 ordered illite-smectite with a 20 to 30% expandable component. Minor phases include kaolinite, chlorite, illite/muscovite, plagioclase, potash feldspar, quartz, dolomite and pyrite. The present illite-smectite was probably originally smectite or highly expandable illite-smectite which underwent conversion to illite-smectite with a low expandable component in a comparatively low-temperature (ca. 100°C) closed-system sedimentary basinal diagenetic environment at a depth of ca. 5 km. Al³⁺ and K⁺ necessary for the conversion reaction were provided through the breakdown of potash feldspar. Burial under a 5 km thick pile of sediments produced some of the observed structures. Whole-rock chemistry presented here suggests that the mudstone formed by severe weathering of acidic source rocks. The influx of freshwater probably flushed out Ba, Rb, Ca and Mn from the restricted basin.  相似文献