Seismotectonics of the Hindukush and Baluchistan arc     

R.K. Verma  M. Mukhopadhyay  A.K. Bhanja 《Tectonophysics》1980,66(4):301-322

A seismicity map of that part of the Pakistan-Afghanistan region lying between the latitudes 28° to 38°N and longitudes 66° to 75°E is given using all available data for the period 1890–1970. The earthquakes of magnitude 4.5 and above were considered in the preparation of this map. On the basis of this map, it is observed that the seismicity pattern over the well-known Hindukush region is quite complex. Two prominent, mutually orthogonal, seismicity lineaments, namely the northvestern and the north-eastern trends, characterize the Hindukush area. The northwestern trend appears to extend from the Main Boundary Fault of the Kashmir Himalaya on the southeast to the plains of the Amu Darya in Uzbekistan on the northwest beyond the Hindukush. The Sulaiman and Kirthar ranges of Pakistan are well-defined zones of intermontane seismicity exhibiting north-south alignment.Thirty-two new focal-mechanism solutions for the above-mentioned region have been determined. These, together with the results obtained by earlier workers, suggest the pre-dominance of strike-slip faulting in the area. The Hazara Mountains, the Sulaiman wrench zone and the Kirthar wrench zone, as well as the supposed extension of the Murray ridge up to the Karachi coast, appear to be mostly undergoing strike-slip movements.In the Hindukush region, thrust and strike-slip faulting are found to be equally prevalent. Almost all the thrust-type mechanisms belonging to the Hindukush area have both the nodal planes in the NW-SE direction for shallow as well as intermediate depth earthquakes. The dip of P-axes for the events indicating thrust type mechanisms rarely exceeds 35°. The direction of the seismic slip vector obtained through thrust type solutions is always directed towards the northeast. The epicentral pattern together with these results suggest a deep-seated fault zone paralleling the northwesterly seismic zone underneath the Hindukush. This NW-lineament has a preference for thrust faulting, and it appears to extend from the vicinity of the Main Boundary Fault of the Kashmir Himalaya on the southeast of Uzbekistan on the northwest through Hindukush. Almost orthogonal to this NW-seismic zone, there is a NE-seismic lineament in which there is a preference for strike-slip faulting.The above results are discussed from the point of view of convergence of the Indian and Eurasian plates in the light of plate tectonics theory.  相似文献   

Effects of non-homogeneity on the stresses in a gravitating sphere     

A. Mukhopadhyay 《Pure and Applied Geophysics》1974,112(1):58-66

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A possible origin of viscosity in Keplerian accretion disks due to secondary perturbation: Turbulent transport without magnetic fields     

Banibrata Mukhopadhyay  Kanak Saha 《中国天文和天体物理学报》2011,11(2)

The origin of hydrodynamic turbulence in rotating shear flow is a long standing puzzle.Resolving it is especially important in astrophysics when the flow's angular momentum profile is Keplerian which forms an accretion disk having negligible molecular viscosity.Hence,any viscosity in such systems must be due to turbulence,arguably governed by magnetorotational instability,especially when temperature T ≥10 5.However,such disks around quiescent cataclysmic variables,protoplanetary and star-forming disks,and t...  相似文献   

GIS-based landslide susceptibility zonation and comparative analysis using analytical hierarchy process and conventional weighting-based multivariate statistical methods in the Lachung River Basin,North Sikkim     

Wadadar  Sudatta  Mukhopadhyay  Bhabani Prasad 《Natural Hazards》2022,110(2):1199-1226

Natural Hazards - The timely and accurate assessment of casualties is the key for and basis of emergency rescue work after an earthquake. In this paper, through exponential fitting of historical...  相似文献   

Transition from radiatively inefficient to cooling dominated phase in two temperature accretion disks around black holes     

Monika Sinha  S. R. Rajesh  Banibrata Mukhopadhyay 《中国天文和天体物理学报》2009,9(12)

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Spatial Estimation of Transmissivity Using Artificial Neural Network   总被引：4，自引：0，他引：4  

Amitabha Mukhopadhyay 《Ground water》1999,37(3):458-464

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Extent and nature of hydrocarbon occurrence in the groundwater of Kuwait     

Eman Al-Awadi  Michael Quinn  Amitabha Mukhopadhyay  Andre Hauser  Adnan Akber  Adel Al-Haddad  Majed Al-Rashedi 《Environmental Geology》2009,56(5):877-889

A study, aimed at characterizing the nature of anthropogenic and biogenic hydrocarbon contamination in the groundwater of Kuwait, was carried out using fluorescence spectroscopy and other analytical techniques. The results of these analyses have demonstrated that the groundwater in certain areas of northern Kuwait has been significantly impacted by contamination originating from the oil-contaminated surface soils. The study revealed that a water-soluble fraction (WSF) of the crude oil surface contamination appeared to be slowly leaching into the freshwater lenses located in the area. The study also showed that hydrocarbon pollutants were practically absent in the brackish water areas of central and southern Kuwait, except for a few isolated sites. However, nonpetroleum hydrocarbons, with ultraviolet-visible absorption characteristics and fluorescence characteristics typically associated with humic substances, were observed at a few sites in the brackish water fields.  相似文献   

Estimates of motion and strain rates across active faults in the frontal part of eastern Himalayas in North Bengal from GPS measurements   总被引：1，自引：0，他引：1  

Mallika Mullick  Federica Riguzzi  Dhruba Mukhopadhyay 《地学学报》2009,21(5):410-415

Within the 2500 km stretch of the Himalayas, a narrow window between longitudes 88.185°E and 88.936°E in the frontal Himalayas in North Bengal, crisscrossed by several active fault traces, presents an interesting region for crustal deformation study. We have estimated velocities of 8 GPS stations located in this area and the accumulating strain rate by two different methods. A total shortening of 11.1 ±1.5 mm yr⁻¹ is occurring across a set of four E–W running faults: Gorubathan, Matiali, Chalsa and Baradighi. The strain rate becomes higher in the NE part of the network, reaching −(0.25 ± 0.12) μstrain yr⁻¹ with azimuth 21°. A statistically significant extension of 10.9 ± 1.6 mm yr⁻¹ is estimated across the Gish transverse fault with a maximum strain rate of 0.36 ± 0.08 μstrain yr⁻¹ with azimuth 103°. The accumulating strain will be probably released through future earthquakes.  相似文献   

Attenuation characteristics of Garwhal–Kumaun Himalayas from analysis of coda of local earthquakes     

Sagarika Mukhopadhyay  Jyoti Sharma 《Journal of Seismology》2010,14(4):693-713

Coda of local earthquakes that occurred during 2006–2007 are used to study the attenuation characteristics of the Garhwal–Kumaun Himalayas. The coda attenuation characteristics are represented in terms of coda Q or Q _c . It is observed that Q _c increases with frequency. Q _c also varies with increase in lapse time of coda waves. Q _c increases up to an 85-s average lapse time. This is similar to observations around the world reported by many workers who have interpreted this as a manifestation of the fact that heterogeneity decreases with depth. However, around a 90-s average lapse time Q _c is lower than its values for lower and higher average lapse times. This is interpreted as an indication of possible presence of a fluid-filled medium or a medium having partial melts at around a 160-km depth. Q ₀, i.e., Q _c at 1 Hz, increases, and frequency parameter n decreases with increasing lapse time, barring around a 90-s lapse time. This again shows that in general, heterogeneity decreases with increasing depth. The Q ₀ and n values for smaller lapse times are similar to those for tectonically active areas. By comparing Q _c values obtained in this study with those obtained by us using the 1999 Chamoli earthquake aftershocks, it is concluded that the crust is turbid and the mantle is more transparent. However, whether the variation in Q _c values between 1999 and 2006–2007 is temporal or not cannot be definitely established from the available data set.  相似文献   

Saddle-shaped reticulate <Emphasis Type="Italic">Nummulites</Emphasis> from Early Oligocene rocks of Khari area,SW Kutch,India     

S Sengupta  Sampa Sarkar  S Mukhopadhyay 《Journal of Earth System Science》2011,120(2):263-268

Saddle-shaped reticulate Nummulites from the Early Oligocene rocks of Khari area, SW Kutch, India is reported here for the first time. Unusual shape of this Nummulites is due to the curved nature of the coiling plane, indicating space constrained postembryonic test growth. With regular development of chambers, septa and septal filaments, the saddle-shaped Nummulites constitutes the third morphotype of N. cf. fichteli Michelotti form A. Other morphotypes of the species reported earlier include inflated lenticular and conical tests. Multiple morphotypes of N. cf. fichteli form A indicates varied test growth in response to substrate conditions. Morphological variability exhibited by N. cf. fichteli form A from Kutch and some Early Oligocene reticulate Nummulites from the Far East are comparable. This faunal suite is morphologically distinct from the contemporary reticulate Nummulites of the European localities.  相似文献